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Significance of female urinary system in obstetrics

The female urinary system is important in obstetrics because changes to the urinary tract during pregnancy can increase the risk of urinary tract infections (UTIs) and other complications:

UTIs: UTIs are the most common bacterial infection during pregnancy, affecting up to 18% of pregnancies. Hormonal and mechanical changes during pregnancy can cause urinary stasis, which increases the risk of UTIs. Untreated UTIs can lead to serious complications for both the mother and fetus, such as preterm labor, low birth weight, and fetal death.
Urinary incontinence: Urinary incontinence (UI) is a common urogenital symptom during pregnancy, affecting between 32% and 64% of pregnant women. UI is usually permanent and can increase toward the end of pregnancy.
Other urogenital symptoms: Other urogenital symptoms during pregnancy include frequency, nocturia, intermittent urination, straining, genital pain, and discomfort.

The urinary system filters waste from the body, regulates blood pressure and volume, and controls electrolyte and metabolite levels.

THE FEMALE URINARY SYSTEM

COMMON TERMS IN URINARY SYSTEM

Proteinuria : Daily excretion of proteins in the urine is more than 150mg. It signifies that the kidney is damaged/ perforated.
Haematuria : Means passing urine containing blood and is due to bleeding into the urinary tract.
Crystalluria : Presence of crystals like oxalates, phosphates in the urine detected by microscopic examination of urine
Glycosuria : Means presence of sugar (glucose) in urine either due to diabetes mellitus or due to renal glycosuria
Azotemia : Increase in the serum concentration of urea and creatinine above their normal values. This occurs when glomerular filtration pressure (GFR) of the kidneys falls due to renal failure. “uremia”.
Oliguria : Diminished urine volume output of urine i.e. 100 mL to 400 mL per day.
Anuria – Complete absence of urine formation i.e zero to 100 mL per day
Dysuria – Difficulty or pain in passing urine
Polyuria – Urine volume above 3 litres per day
Retention of urine – occurs due to obstruction of urine outflow from the bladder, this is relieved by catheterization

Anatomy of the Renal System

The urinary system is the main excretory system eliminating waste products from blood through urine.

Its anatomy consists of two kidneys, each joined to the bladder by the tube called ureter, which conveys urine from the kidneys to the bladder for storage. Following bladder contraction, urine is expelled through the urethra.

The Kidneys

There are two kidneys which lie behind the peritoneum on either side of the vertebral column. In adults, they measure approximately 12 to 14 cm.

The urine is formed in the kidney by the nephrons.

Each kidney has approximately one million nephrons.

Role of the Kidneys

• Influence blood pressure control

• Release renin to activate the renin-angiotensin system

• Can lead to water retention or excretion

• Waste excretion(Urea, Creatinine, Uric Acid)

• Blood filtration

• Blood glucose regulation(glucose absorption)

• Acid Base Balance/pH regulation

• Electrolyte balance (Sodium, Potassium, Chloride)

•Erythropoiesis regulation(also produces Erythropoietin)

URINARY BLADDER

It is made up of four layers i.e.

Mucosa; this is the innermost layer with rugae that allows its distention.
Sub mucosa which provides rich vascular supply
Smooth muscle layer/ detrusor muscle; which contracts during urination for urine expulsion.
Serosa: a continuation of peritoneum

The bladder has a triangular area called trigone with three openings at its angles i.e two for ureters laterally and one for the urethra at the apex

URETHRA

This conveys urine from the urinary bladder to outside of the body.

The internal sphincter of smooth muscle and external urethral sphincter of skeletal muscles constricts the lumen of the urethra causing bladder to fill.

Female urethra is 4cm long and male urethra is 20 cm

NEPHRON

This is a functional (urine) forming units of the kidneys

Components of the Nephron

Bowman’s Capsule a cup-like structure made of squamous epithelium and inner layer has modified cell (podocytes) closely associated with glomerular capillaries
Glomerulus made of highly permeable capillary network
Proximal convoluted tubule, made of cuboidal epithelium with microvilli. It is a primary site of tubular reabsorption and secretion mechanisms.
Loop of Henle, both ascending and descending loops are involved in urine concentration
Distal Convoluted tubule; this is shorter than the proximal and contains macula densa specialized sensory cells which monitor NaCl concentrations. it’s a site of tubular reabsorption and secretion
Collecting Ducts; these empty urine into the renal pyramids

Physiology of the urinary system

The volume of the urine excreted per day is about 1500m/s or roughly 1 ml /min. The processes responsible for urine formation are ultra filtration at the glomeruli and reabsorption in the tubules of the nephrons.

The kidneys are largely responsible for maintaining this constancy and the excretion of waste products of metabolism.

For example, urea which is a waste product of protein metabolism is excreted in a large quantity. Various renal functions are illustrated below

FUNCTIONS OF THE RENAL SYSTEM

Regulation of the water content of the body: About 2/3 of water filtered by the glomeruli is reabsorbed in the proximal tubules iso-osmotically. The remaining water is reabsorbed in distal tubules and collecting duct; under the influence of antidiuretic hormone (ADH).
Regulation of normal acid-base balance of the blood. The kidneys help to maintain a normal internal environment by preventing body fluids from becoming too acidic or too alkaline.
Regulation of electrolyte content of the body. A large part of sodium ions (Na+), chloride ions (Cl- ) are actively reabsorbed in the PCT, DCT and collecting ducts. The kidney regulates the fluid balance by excreting more urine when a large amount of urine is taken and retains fluid when much has been lost.
Hormonal and metabolic functions. The kidney produces many hormones which take part in various metabolic functions >Renin is produced in the “Juxta glomerular apparatus” and stimulates aldosterone secretion.

> Erythropoietin – stimulates red blood cells production
> Prostaglandins produced in the kidneys help in vasodilation of blood vessels.

Processes Involved in urine formation

Filtration
Selective Reabsorption
Tubular Secretion

FILTRATION

This takes place through the semipermeable walls of the glomerulus and glomerular capsule/Bowman’s Capsule. Water and other small molecules pass through, although some are reabsorbed later. Blood cells, plasma proteins and other large molecules are too large to filter through and therefore remain in the capillaries.

Filtration takes place because there is a difference between the blood pressure in the glomerulus and the pressure of the filtrate in the glomerular capsule.

Because the afferent arteriole is narrower than the afferent arteriole, a capillary hydrostatic pressure builds up in the glomerulus. This pressure is opposed by the osmotic pressure of the blood, provided mainly by plasma proteins, and by filtrate hydrostatic pressure in the glomerular capsule,

The volume of filtrate formed by both kidneys each minute is called the glomerular filtration rate (GFR). In a healthy adult the GFR is about 125 ml/min, i.e. 180 liters of filtrate are formed each day by the two kidneys. Nearly all of the filtrate is later reabsorbed from the kidney tubules with less than 1%, i.e. 1 to 1.5 liters, excreted as urine. The differences in volume and concentration are due to selective reabsorption of some filtrate constituents and tubular secretion of others

SELECTIVE REABSORPTION

Most reabsorption from the filtrate back into the blood takes place in the proximal convoluted tubule, whose walls are lined with microvilli to increase surface area for absorption.

Materials essential to the body are reabsorbed here, including some water, electrolytes and organic nutrients such as glucose. Some reabsorption is passive, but some substances are transported actively. Only 60–70% of filtrate reaches the loop of the nephron.

Much of this, especially water, sodium and chloride, is reabsorbed in the loop, so only 15–20% of the original filtrate reaches the distal convoluted tubule, and the composition of the filtrate is now very different from its starting values. More electrolytes are reabsorbed here, especially sodium, so the filtrate entering the collecting ducts is actually quite dilute. The main function of the collecting ducts therefore is to reabsorb as much water as the body needs.

TUBULAR SECRETION

Filtration occurs as the blood flows through the glomerulus.

Substances not required and foreign materials, e.g. drugs including penicillin and aspirin, may not be cleared from the blood by filtration because of the short time it remains in the glomerulus.

Such substances are cleared by secretion from the peritubular capillaries into the convoluted tubules and excreted from the body in the urine.

Tubular secretion of hydrogen ions (H+) is important in maintaining normal blood pH.

Effects of a Full Bladder in Labor

A full bladder during labor can have several negative consequences:

Compression of the bladder: The fetal head can compress the bladder, leading to bruising and edema.
Delayed descent of the presenting part: A full bladder can impede the descent of the baby.
Increased pain and prolonged labor: A full bladder contributes to discomfort and can lengthen labor.
Delayed placental delivery: A full bladder can hinder placental expulsion.
Retained products of conception and postpartum hemorrhage (PPH): A full bladder increases the risk of retained placental fragments and subsequent PPH.
Increased risk of urinary tract infections (UTIs) during the puerperium (postpartum period): Urinary stasis increases the chance of infection.
Vesicovaginal fistula: In severe cases, prolonged pressure can lead to the formation of a fistula between the bladder and vagina.

Importance of the Urinary Bladder in Midwifery (During Pregnancy, Labor, and Puerperium)

Frequency of Micturition:

First trimester: Frequent urination is due to the pressure of the growing uterus on the bladder.
Second trimester: Frequency may be caused by UTIs, resulting in dysuria (painful urination).
Late pregnancy: Frequency is often due to the presenting part descending into the pelvis.
Labor: Frequent urination can be caused by malpositions (e.g., occipital posterior position) and increased fluid intake, as well as pressure from the presenting part.
Puerperium: Frequency occurs due to autolysis (self-digestion of tissues) and ischemia (reduced blood flow) as the body eliminates waste products.

Retention of Urine:

Pregnancy: Retention can be caused by retroversion of the uterus.
Labor: The bladder lumen is pulled upward due to elongation of the urethra.
Puerperium: Retention is often due to pain after episiotomy and nerve injury during delivery.

Incontinence of Urine:

Pregnancy: Incontinence can result from relaxation of the pelvic floor muscles, causing urine leakage with coughing, sneezing, or laughing.
Labor: Incontinence is often due to the descending presenting part.
Puerperium: Incontinence may be due to pelvic floor injuries, such as vesicovaginal fistula.
Stress incontinence: This is caused by increased intra-abdominal pressure.

Prevention of Urinary Complications

During Pregnancy:

Avoid using traditional medicines that weaken pelvic floor muscles.

During Labor:

Keep the bladder empty.
Avoid overstretching of the pelvic floor muscles.
Perform episiotomy when necessary.
Avoid prolonged labor; consider Cesarean section to prevent injuries.

During Puerperium:

Perform postnatal exercises like Kegel exercises.
Treat any infections, such as UTIs.
Delay sexual intercourse until after the postpartum period.

Physiology of Micturition (Urination)

The sensation of a full bladder is transmitted to the brain via sensory sympathetic nerves. When it is appropriate to urinate:

Voluntary nerves relax the membranous sphincter.
Sympathetic nerves relax the internal sphincter.
Parasympathetic nerves cause the detrusor muscles to contract, pulling on the pubovesical muscle and opening the internal urethral meatus.
Intra-abdominal pressure increases, and urine is passed with a bearing-down movement. The bladder pressure increases rapidly once its volume exceeds approximately 400-500 ml.

Clinical Procedure: Catheterization

Scenario: A mother in labor has contractions with delayed descent of the presenting part, possibly due to a full bladder.

Task: Carry out catheterization.

Objectives:

State indications for catheterization.
Prepare the requirements for passing a urethral catheter.
Perform the procedure of passing a urethral catheter.

Indications for Catheterization:

To obtain a urine specimen for investigation.
To facilitate descent of the presenting part.
To prevent retention of products of conception and PPH.
To ensure an empty bladder before surgery to avoid injury.

Catheterization Procedure

Top Shelf:

A sterile park containing:

Towel
Drape 1
Receiver 2
Gauze swabs
Cotton wool swabs
Gallipot 2

Bottom Shelf:

Two Foley catheters of required sizes.
Spigot and drainage bag.
Sterile water.
Antiseptic lotion.
Sterile surgical gloves.
3 receivers.
Sterile water and needle.
Specimen bottles.
Mackintosh apron.
Syringes of sterile water.
Plastic sterile chart.
Strapping.
Measuring jar.

Bed Side:

Screens
Hand washing equipment
Basin
Soap.
Hand towel.

EXAMINER’S CHECKLIST.

Station:

Scenario: FEMALE CATHETERISATION.

Examiner’s name ………………………………………..…date………………………………..

School code……………………………………………………candidate’s No……………………………

NO.	AREAS TO BE ASSESSED	SCORE	DONE	PARTIALLY DONE	NOT DONE	TOTAL
1	Creates rapport with the patient.	½
2	Explains the procedure	½
3	Screens the bed and extends the trolley to the bed side.	½
4	Puts the small mackintosh and towel to protect the linens	½
5	Washes hands methodically and puts on surgical gloves.	1
6	Inspects and cleans the vulva in a methodical way.	1
7	Drapes the mother	½
8	Selects the appropriate catheter and lubricates the tip with k.y jelly.	½
9	Place the receiver in between the thighs and puts the catheter, inserts slowly until urine is seen emptying into the receiver	1
10	Injects into the catheter to balloon it and aid it remain in situ.	1
11	Connects the catheter to the urinary bag and Fastens it on the thigh	1
12	Removes the receiver, drape, and small mackintosh.	½
13	Measures the urine collected and records in the fluid balance chart.	½
14	Clears away, leaves the mother comfortable and thanks her.	½
15	Washes hands and documents the findings.	½
	TOTAL	10

Examiner’s comments………………………………………………………………………………………………………

Revision Questions

Explain the role of the sympathetic nerves.
Outline the different parts of the kidney.
Explain the endocrine activity of the kidneys.
Explain the role of the renin-angiotensin system.
State five functions of the kidneys.
Explain the functional part of the renal system.
Describe the gross structure of the bladder.
Describe the microscopic structure of the bladder.
State two functions of the urinary bladder.
Outline the relations of the bladder.
Explain the three processes of production of urine.
Describe the urethra.
Explain the importance of the urinary bladder during pregnancy.
Explain the importance of the urinary bladder in labor.
Outline the importance of the urinary bladder during the puerperium.
List seven effects of a full bladder in labor.
Explain the prevention of complications of the renal system during pregnancy.
List five ways how complications of the renal system can be prevented during pregnancy.

Significance of female urinary system in obstetrics Read More »

FETAL SCALP TISSUE

The scalp refers to the layers of skin and subcutaneous tissue that cover the bones of the cranial vault.

This is a soft outer covering of the fetal skull.

Structure of the Scalp Tissue

Consists of five layers.

The mnemonic ‘SCALP’ can be a useful way to remember the layers of the scalp: Skin, Dense Connective Tissue, Epicranial Aponeurosis, Loose Areolar Connective Tissue and Periosteum.

1. SKIN: It is the outer covering and contains hair. contains numerous hair follicles and sebaceous glands (thus a common site for sebaceous cysts).

It’s thicker than skin on most other parts of the body, densely populated with hair follicles, sebaceous (oil) glands, and sweat glands.
The abundance of sebaceous glands makes the scalp prone to sebaceous cysts.
The skin’s rich blood supply contributes to its rapid healing capabilities but also makes it susceptible to significant blood loss during trauma.

2. DENSE CONNECTIVE TISSUE (SUPERFICIAL FASCIA): This is the subcutaneous layer made of fibrous fat tissue. This layer, immediately beneath the skin, is composed of dense fibrous connective tissue interwoven with fat.

This layer is highly vascular, containing numerous blood vessels that nourish the hair follicles and the scalp itself.
Its fibrous nature makes it strong and resilient but also contributes to the difficulty of separating it from the underlying layers.
In prolonged or difficult labor, it can become edematous (swollen) and accumulate fluid, resulting in a caput succedaneum—a soft, fluctuant swelling that typically resolves without intervention.

3. EPICRANIAL APONEUROSIS OR MUSCLE LAYER(GALEA APONEUROTICA): A thin, tendon-like structure that connects the occipitalis and frontalis muscles. It is a layer of tendon covering the vertex.

It connects the frontalis muscle of the sinciput and the occipitalis muscle of the occiput. This is known as the tendon of Galea.
The aponeurosis plays a crucial role in scalp mobility and protects the underlying tissues from excessive movement. It firmly adheres to the underlying layers and its strong composition prevents widespread injury.

4. LOOSE AREOLAR CONNECTIVE TISSUE (SUBAPONEUROTIC LAYER):
This is the layer of loose connective tissue covering the areola which permits limited movements of the scalp to occur over the skull.

A thin connective tissue layer that separates the periosteum of the skull from the epicranial aponeurosis.
This allows for the scalp’s considerable mobility over the skull, an important protective mechanism against trauma.

5. PERIOSTEUM: The periosteum is the thin, fibrous membrane that tightly adheres to the outer surface of the cranial bones.

This covers the outer surface of the bone and it envelops each bone separately.
It is a vascular layer supplying the cranial bone with blood.
Because it is tightly adherent to the skull, it resists separation, unlike the subaponeurotic layer.
During difficult births, where some forces are applied to the fetal head, rupture of the blood vessels in this layer can cause a cephalohematoma—a collection of blood that is confined to the region of one or more bones.
Unlike caput succedaneum, a cephalohematoma is confined by the sutures of the skull.

Blood Supply, Lymphatic Drainage, and Innervation:

The scalp receives blood supply primarily from the external and internal carotid arteries.

Lymphatic drainage from the scalp is intricate and occurs in multiple regions with connections to pre-auricular and posterior auricular lymph nodes.

Innervation of the scalp, comes from various cranial nerves:

Greater occipital nerve: supplies the posterior vertex
Lesser occipital nerve: supplies the posterior scalp near the ear
Auriculotemporal nerve: supplies the temporal region and part of the mandible
Supraorbital nerve: supplies the forehead above the orbit
Supratrochlear nerve: supplies the medial forehead
Zygomatic temporal nerve: supplies the lateral temporal region

BIRTH INJURIES INVOLVING THE SCALP

CAPUT SUCCEDANEUM

Caput succedaneum is an oedematous swelling on the subcutaneous layer of the scalp of the fetal skull. It is a swelling which contains serum.

Caput succedaneum is a collection of serum (fluid) that causes a soft, edematous (swollen) area on the baby’s scalp. It’s located in the subcutaneous layer (beneath the skin).

Causes of Caput Succedaneum

Pressure from the cervix (the lower part of the uterus) during labor causes slowed blood flow and fluid buildup in the scalp. This is especially likely if the membranes (bag of waters) have ruptured early and are not protecting the fetal head.

It is due to pressure of the dilating cervix to the girdle of contact following early rupture of membranes. Since the fore water is not there to take away the pressure of the dilating cervix off the fetal head.
The pressure of the dilating cervix causes various blood supply retardation and the area lying over the internal os becomes congested and oedematous.
The size of the swelling depends on the degree of cervical dilatation.

Predisposing Factors of Caput Succedaneum

Any condition causing early rupture of membranes during labour e.g.

Mal presentations like breech presentations and transverse lie.
Mal positions like occipital posterior position, face brow.
In vacuum extraction when the vacuum extractor cup causes pressure on the scalp. Incases where a vacuum extractor was used, the swelling is called a Chignon.

Characteristics of a caput succedaneum

This swelling develops during labour therefore it may be felt on vaginal examination.

Develops during labor; it may be noticeable during vaginal exams.
Present at birth.
Can cross the suture lines (the joints between the baby’s skull bones) — unlike cephalohematoma which is confined by these sutures.
Usually gets smaller over time.
Leaves an indentation when pressed (because of the fluid).
Typically disappears within 24-36 hours. This is a key differentiator between caput succedaneum and cephalohematoma.
More common than cephalohematoma.
Contains serum (fluid), not blood.

Management of Caput Succedaneum

The HCW must reassure the mother and tell her that this is a temporary condition.
No treatment is needed unless the caput is excessive in size.
No local treatment should be applied.
Injection vitamin k 1mg can be administered especially when mother went through difficult labour and the baby is cot nursed for at least 24 hours depending on the severity of the condition.
The baby is observed carefully for signs of cerebral irritation.

CEPHALOHEMATOMA

A cephalohematoma is a swelling on the fetal skull due to the effusion (collection) of blood under the Periosteum (pericranium) covering the bone of the fetal skull.

A cephalohematoma is a collection of blood (hematoma) that forms between the periosteum and the skull bone. Slight separation of the periosteum from the bone allows blood to accumulate. Unlike caput succedaneum, it is contained by the sutures of the skull and does not cross suture lines.

Causes Of Cephalohematoma

Friction between the fetal skull and the mother’s pelvis during delivery.
Cephalopelvic disproportion (baby’s head is too large for the birth canal).
Precipitous labour (very rapid labour).
Persistent posterior position of the baby’s head (occiput posterior).
Excessive moulding of the fetal head (the skull bones overlap during labour). These factors cause tearing of the periosteum, leading to bleeding.

All the above conditions cause tearing of the Periosteum from the bone leading to bleeding.

Characteristics of Cephalohematoma

Unlike caput succedaneum, it is not present at birth; it typically appears within 12-24 hours after delivery.
It does not cross suture lines because the periosteum is attached along the suture lines. This is a key difference from caput succedaneum. It can, however, be bilateral (on both sides of the head).
It tends to increase in size over several days and can persist for weeks (at least 6 weeks, or longer).
Does not indent/pit with pressure (unlike the edematous caput succedaneum).
Usually resolves spontaneously through reabsorption.

Management and Treatment of Cephalohematoma

Observation: Usually, no specific treatment is required, provided the cephalohematoma is not increasing in size rapidly or causing other issues. Close observation is key.
Vitamin K: In some cases, a Vitamin K injection (1mg) may be administered to a full-term infant to improve blood clotting. This is especially pertinent in the event of difficult labor or clinical concern about blood clotting. The clinical circumstances determine this decision, and is not uniformly recommended.
Hemoglobin Levels: The infant’s hemoglobin levels should be monitored; if anemia is present, hematinics (iron supplements or other blood-building medications) may be prescribed.
Blood Transfusion: In cases of severe anemia, a blood transfusion might be necessary.
Reassurance: Parents should be reassured that this is usually a benign condition that resolves on its own. They should be instructed not to puncture the swelling.

Rare Complications:

Although rare, potential complications include:

Meningitis (infection of the brain and spinal cord membranes) – This would be secondary to another infection and is not directly caused by the cephalohematoma itself.
Neonatal tetanus (rare, only if the swelling is broken, allowing infection)
Anemia (low red blood cell count)

Note: Care should be taken not to injure the Scalp features because they can bleed profusely since they are well supplied with blood.

Importance of the knowledge of the fetal skull During Pregnancy

It is an easily recognized part of the fetus so the midwife being aware of the size and shape locates it and builds up her concept of the fetus as a whole.
Size compared with the height of fundus. The fetal skull helps the midwife to assess the period of gestation.
The fetal skull is used to assess the rate of growth, normal or small for dates.
The presentation is identified by the fetal head. In cephalic presentation, it is found over the pelvis in the lower pole of the uterus. In Breech presentation, it’s found in the fundus.

During Labour

The knowledge of the fetal skull gives midwife indication to the outcome of labour.
The level of descent is estimated on abdominal palpation in order to assess the progress of labour.

Vaginal examination

The level of the presenting part is compared to the ischial spine. If the head is above the ischial spines, it is not yet engaged. If the head is at the level of the ischial spine, it is engaged and the outcome is good.
In the flexed head the occiput will be found lower than the same level with a flexed head the occiput will be at the ischial pines.

Revision Question

What is scalp tissue?
List five layers of the scalp tissue from inside out.
State two common injuries of the scalp tissue.
Give four characteristics of a caput succedaneum.
Explain two causes of a cephalohematoma.
Outline eight differences between a caput succedaneum and a Cephalohematoma.

THE ANATOMY OF THE INTERNAL STRUCTURES OF THE FETAL SKULL

Nervous system: It is a network of nerve cells and fibres which transmits nerve impulses between parts of the body. It is a central processing unit of the body and also controls and balances the body functions.

Divisions

Central Nervous System (CNS): Comprises the brain and spinal cord, the primary control centers.
Peripheral Nervous System (PNS): Consists of nerves that extend from the CNS to all parts of the body, relaying information to and from the CNS.
Autonomic Nervous System (ANS): A part of the PNS that regulates involuntary functions like heart rate, digestion, and breathing. It further subdivides into the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) systems.

Internal Structures of the Fetal Skull

The fetal skull houses the;

developing brain,
its protective coverings (meninges),
fluid-filled spaces (ventricles), and
the blood vessels that supply it.

A. THE BRAIN:

The brain, the largest part of the CNS, resides within the cranial cavity. It is divided into three main parts: Cerebrum (fore head), Cerebellum (hindbrain) and Brain stem consists of the midbrain, pons varolii and medulla oblongata.

Cerebrum: The largest part, filling most of the cranial vault. It is divided into two hemispheres (right and left), each controlling the opposite side of the body. Each hemisphere is further subdivided into lobes:

Frontal Lobe: Responsible for higher-level cognitive functions like planning, decision-making, and voluntary movement.
Parietal Lobe: Processes sensory information (touch, temperature, pain).
Temporal Lobe: Involved in auditory processing, memory, and language comprehension.
Occipital Lobe: Processes visual information.

The surface of the cerebrum is highly folded, increasing its surface area. The folds are called gyri, and the grooves separating them are called sulci. The outer layer is gray matter (neuronal cell bodies), while the inner layer is white matter (axons).

Cerebral Functions

The cerebrum is the center for higher mental functions such as intellect, memory, willpower, imagination, emotions, and reasoning. It receives and interprets sensory stimuli, initiates voluntary movements, and controls other parts of the nervous system.
Receive and perceive the stimuli i.e. It contains sensory centres which give sensitivity to the skin, muscles, bones and joints.
It contains centres for special senses e.g. sight, hearing, smell, taste and touch.
To give command for reaction with the help of past experience.
To control other parts of the nervous system.

Cerebellum: Located beneath the cerebrum, the cerebellum is smaller but crucial for coordination and balance.

It has two hemispheres and consists of an outer layer of gray matter and an inner layer of white matter.
Situated below and behind the cerebrum.
It is the hindbrain.
It is smaller than the cerebrum.
It consists of the grey matter on the outside and white matter inside due to axons.

Functions of cerebellum

The cerebellum coordinates muscle movements, maintains posture and balance, and contributes to smooth, precise motor control.
Controls muscle tone and maintains equilibrium. (Helps balancing the body)
Helps coordination of body movements.
Damage to the cerebellum leads to ataxia (loss of coordination), causing clumsy movements and impaired balance.

Clinical note

Destruction of the cerebellum by disease results in loss of power to coordinate muscular activity therefore the movements are exaggerated and awkward e.g. a full cup cannot be lifted to drink without spilling the fluid, patient cannot walk or stand steadily but staggers and moves like a drunkard man.

Brainstem: It is comparatively very small and occupies the back lower part of the cranial cavity.

Connects the cerebrum and cerebellum to the spinal cord. It consists of:

Midbrain: It is found under the cerebrum.
It contains nerve fibres that connect the cerebrum with the lower parts of the brain and the spinal cord. Relays signals between the cerebrum and lower brain centers.
Pons: It is the central part of the CNS just above the spinal cord.
A relay center for signals between the cerebrum, cerebellum, and medulla oblongata; also involved in regulating breathing. Also plays part in control of consciousness, control level of concentration.
Medulla Oblongata: Extends from the pons and is continuous with the spinal cord.
Controls vital functions such as breathing, heart rate, and blood pressure. It contains vital centers whose damage can lead to immediate death. Reflex centers for swallowing, vomiting, coughing, and sneezing are also located here.
Any injury to it causes instant death.

General Functions of Nervous system

Control over voluntary and involuntary functions / actions.
To control body movements, respiration, circulation, digestion, hormone secretion, body temperature.
To receive stimuli from sense organs, perceive them and respond accordingly.
Higher mental functions like memory, receptivity, perception & thinking.

B. THE CEREBRAL MEMBRANES/MENINGES

The brain and the spinal cord are covered by three membranes arranged from out inward, these cover and protect the brain. They are; Dura (outer), Arachnoid matter (middle) and Pia matter (inner).

Dura Mater: The outermost, thickest, and toughest layer. It has two layers:
the periosteal layer (attached to the skull) and the meningeal layer (covering the brain).
Extensions of the dura mater, the falx cerebri (separates the cerebral hemispheres) and the tentorium cerebri (separates the cerebrum from the cerebellum), further protect the brain.
Arachnoid Mater: A delicate, web-like middle layer. The subarachnoid space, between the arachnoid and pia mater, contains cerebrospinal fluid (CSF).
Pia Mater: The innermost, thin, and highly vascular layer adhering directly to the brain’s surface, providing it with blood supply.

C. THE VENTRICLES

The brain contains four interconnected cavities, the ventricles, filled with CSF. The CSF cushions and protects the brain and spinal cord. CSF is produced in the ventricles and circulates throughout the subarachnoid space.

The brain is not solid but contains four cavities known as ventricles.

There are two lateral ventricles on either hemispheres of the cerebrum.
The third lies in the midline of the cerebrum, the fourth is between the pons, medulla oblongata and cerebellum.
These ventricles communicate with one another and contain the cerebral spinal fluid.
This fluid is secreted in the four chambers and they have openings where the cerebrospinal fluid flows from one ventricle to the other. It flows into the subarachnoid space and the straight canal of the spinal cord through the opening of the fourth ventricle.

THE CEREBRAL SPINAL FLUID

CSF is a clear, colorless fluid that circulates within the ventricles of the brain, the subarachnoid space (between the arachnoid and pia mater), and the central canal of the spinal cord.
In adults, the total volume is approximately 130-150 mL, and it is continuously produced and reabsorbed. Its specific gravity is 1.004-1.008.

Composition of CSF:

CSF is primarily composed of water, but also contains glucose, proteins, electrolytes (sodium, potassium, chloride, calcium, magnesium), amino acids, and a small number of cells (mostly lymphocytes).
Its composition closely reflects the plasma, but with significant differences in protein and cell content.

Production and flow of CSF

CSF is primarily produced by the choroid plexus, a network of specialized capillaries and ependymal cells lining the ventricles.
The choroid plexus actively secretes CSF through a process involving ion transport and filtration.

The flow of CSF is as follows:

Lateral Ventricles: CSF is produced in the lateral ventricles (two), the largest ventricles.
Interventricular Foramina (Foramina of Monro): CSF flows from the lateral ventricles through the interventricular foramina into the third ventricle.
Cerebral Aqueduct (Aqueduct of Sylvius): CSF passes through the narrow cerebral aqueduct, located in the midbrain, into the fourth ventricle.
Fourth Ventricle: CSF flows from the fourth ventricle through three openings: the median aperture (foramen of Magendie) and two lateral apertures (foramina of Luschka).
Subarachnoid Space: CSF enters the subarachnoid space, surrounding the brain and spinal cord.
Arachnoid Granulations (Villi): CSF is reabsorbed into the venous system via arachnoid granulations, small protrusions of the arachnoid mater that extend into the superior sagittal sinus (a major intracranial venous channel).

Clinical Significance – Hydrocephalus:

Blockage of CSF flow at any point in the circulation can lead to hydrocephalus, a condition characterized by an accumulation of CSF within the ventricles and/or subarachnoid space, causing increased intracranial pressure.

Congenital Hydrocephalus: Results from developmental anomalies affecting the ventricles or their outflow pathways.
Acquired Hydrocephalus: Can be caused by various factors including tumors, infections (meningitis, encephalitis), head trauma, and hemorrhage.
Communicating Hydrocephalus: Obstruction occurs after the CSF leaves the ventricular system. The problem lies in the impaired absorption of CSF through the arachnoid granulations.
Non-Communicating (Obstructive) Hydrocephalus: Obstruction occurs within the ventricular system, often at the level of the foramina of Monro, cerebral aqueduct, or foramina of Luschka and Magendie.

Functions of CSF:

Buoyancy and Protection: CSF reduces the effective weight of the brain, preventing it from being crushed by its own weight. It also acts as a shock absorber, protecting the brain and spinal cord from trauma.
Homeostasis: CSF helps maintain a stable chemical environment for the brain and spinal cord by regulating the extracellular fluid composition.
Nutrient Transport: CSF transports nutrients and removes metabolic waste products from the brain.
Excretion: CSF assists in the removal of waste products from the brain.

SPINAL CORD

The spinal cord is a long, cylindrical structure extending from the medulla oblongata to the level of the first or second lumbar vertebra (L1-L2).
It is approximately 45 cm long in adults and is encased within the vertebral canal of the spine. 31 pairs of spinal nerves branch off from the spinal cord.

Functions of spinal cord

Sensory Transmission: Carries sensory information from the body to the brain.
Motor Transmission: Transmits motor commands from the brain to the muscles and glands.
Reflex Actions: Mediates reflex actions (involuntary responses to stimuli), allowing rapid responses without the involvement of the brain.

Intracranial Blood Sinuses

It is important to note that the draining territories of intracranial veins are different from those of arterial territories of the major cerebral arteries.

Intracranial venous sinuses are channels located within the dura mater. Unlike other veins in the body they run alone and not parallel to arteries, they lack valves and have rigid walls. Their drainage patterns differ significantly from those of the cerebral arteries. They ultimately drain blood into the internal jugular veins.

The key sinuses include:

Superior Sagittal Sinus: Runs along the superior border of the falx cerebri, from the crista galli to the internal occipital protuberance. It receives superior cerebral veins and veins from the pericranium (outer layer of the scalp).
Inferior Sagittal Sinus: Runs along the inferior border of the falx cerebri.
Straight Sinus: Formed at the junction of the inferior sagittal sinus and the great cerebral vein of Galen.
Great Cerebral Vein of Galen: A large vein draining the deep structures of the brain.
Transverse Sinuses: Two sinuses running horizontally across the posterior cranial fossa, along the line of attachment of the tentorium cerebri to the occipital bone.
Sigmoid Sinuses: Continuations of the transverse sinuses that descend into the neck as the internal jugular veins.

Revision questions

Explain the features of the cerebrum.
Outline the features of the cerebellum.
Describe the Mid brain.
Outline three functions of the cerebellum.
Explain five functions of the cerebrum.
State two functions of the medulla oblongata.
Outline five cerebral sinuses.
With the use of a table, explain the situation and functions of;
I. Meninges.
ii. Cerebral ventricles.
iii. Cerebral spinal fluid.
State two contents of the cerebral spinal fluid.
List four lobes of the brain.
List two functions of the pons varolli.

FETAL SCALP TISSUE AND THE ANATOMY OF THE INTERNAL STRUCTURES OF THE FETAL SKULL Read More »

FETAL CIRCULATION

Fetal circulation is the process by which a fetus in utero receives nutrients and oxygen from the placenta for growth and development.

In utero, the fetus relies on the placenta for respiration, nutrition, and excretion. The lungs are non-functional because they are sealed off by membranes, and blood from the placenta is already oxygenated.

Important Notes:

The fetus develops its own blood during intrauterine life; it does not mix with maternal blood except in pathological situations.
The fetus produces its own red and white blood cells.
During intrauterine life, the fetal gastrointestinal and respiratory systems are non-functional. The fetus obtains nutrients and oxygen from maternal blood through diffusion and osmosis, facilitated by the selective action of the cytotrophoblast and syncytiotrophoblast.

Blood Circulation in Temporary Structures:

(i) Umbilical Vein: Blood from the placenta, 80% saturated with oxygen and nutrients, is transported to the fetus via the umbilical vein. It branches in the liver, joining the portal vein and supplying the liver. This is the only vessel in the fetus carrying unmixed blood.

(ii) Ductus Venosus: Connects the umbilical vein to the inferior vena cava. Here, the blood mixes with partially oxygenated blood returning from the lower body.

(iii) Foramen Ovale: Approximately 75% of the mixed blood passes through this temporary opening between the two atria. This diversion occurs because the blood is already oxygenated and doesn’t need to go to the lungs. A small amount of blood flows through the pulmonary artery to the lungs (to maintain viability) and returns to the left atrium via the pulmonary vein. 25% of this blood enters the left ventricle and then the aorta. The heart and brain receive relatively well-oxygenated blood because the coronary and carotid arteries are early branches. The arms are more developed than the legs at birth because they receive oxygenated blood from the aorta.

(iv) Ductus Arteriosus: Moves blood from the pulmonary artery to the descending aorta, entering just beyond where the subclavian and carotid arteries branch from the aorta.

(v) Hypogastric Arteries: Blood then flows to the hypogastric arteries (branches of the internal iliac arteries), becoming the umbilical arteries, which return approximately 15% oxygen-saturated blood to the placenta for re-oxygenation.

Simplified Flow:

Oxygenated blood from the mother enters the placenta.
Oxygenated blood travels via the umbilical vein to the fetus.
Most of this blood bypasses the liver via the ductus venosus.
The blood enters the inferior vena cava.
Most of the blood flows through the foramen ovale into the left atrium.
The blood is then pumped to the rest of the body.
Deoxygenated blood returns to the heart.
Some blood goes to the lungs, but most is shunted via the ductus arteriosus to the aorta.
Deoxygenated blood travels back to the placenta through the umbilical arteries.

Mnemonic:

P-U-D-I-F-D-U (sounds like “Poo-dee-fid-you”):

Placenta: Receives oxygen from mom
Umbilical Vein: Brings oxygen to baby
Ductus Venosus: Bypasses liver
Inferior Vena Cava: Blood mixes
Foramen Ovale: Bypasses lungs
Ductus Arteriosus: Bypasses lungs again
Umbilical Arteries: Returns blood to placenta

Changes After Birth and Adaptation to Extrauterine Life:

Physiological changes after birth are initiated by inspiration and cutting/clamping of the umbilical cord.

Clamping the cord stops circulation through the umbilical vein, causing it to collapse. Its abdominal portion thromboses and occludes, forming the fibrous ligamentum teres, running from the umbilicus to the liver, enclosed in the falciform ligament.
These changes lead to the collapse of the ductus venosus, which becomes the ligamentum venosum. Umbilical vein collapse reduces atrial pressure.
The onset of respiration and pulmonary circulation increases right atrial pressure, closing the foramen ovale flap-like valve, which seals to form the fossa ovalis.
When the neonate cries, lung expansion increases the vascular field. Blood that previously flowed through the ductus arteriosus to the aorta now flows through the pulmonary artery to the lungs for oxygenation. The ductus arteriosus becomes the ligamentum arteriosum.
The hypogastric arteries contract, becoming obliterated; however, the first few inches remain patent, forming the internal iliac and superior vesicle arteries. The baby now receives nutrients through feeding and eliminates waste via the kidneys and gastrointestinal system.

CONGENITAL HEART DEFECTS (ANOMALIES)

1. Ventricular Septal Defect (VSD): Incomplete closure of the wall between the two ventricles results in mixing of oxygenated and deoxygenated blood, flowing from left to right. These defects often close spontaneously during childhood or adolescence. Large defects, however, can lead to pulmonary hypertension due to increased blood flow through the pulmonary circulation.

2. Atrial Septal Defect (ASD): Incomplete closure of the wall between the two atria causes blood mixing. The right side of the heart handles a larger-than-normal blood volume, leading to hypertrophy. Excess blood flows through the pulmonary artery to the lungs, causing higher-than-normal pressure in the pulmonary blood vessels and potentially congestive heart failure. Treatment involves open-heart surgery.

3. Patent Ductus Arteriosus (PDA): Failure of the ductus arteriosus to close creates a communication between the aortic arch and the pulmonary artery. A large, persistent PDA increases pulmonary artery pressure, potentially leading to Eisenmenger’s syndrome—a reversal of flow (right-to-left shunt). Congestive heart failure may necessitate medication to inhibit prostaglandins and promote ductus arteriosus closure.

4. Transposition of the Great Vessels: The aorta and pulmonary artery are reversed. The aorta receives poorly oxygenated blood from the right ventricle and delivers it to the body without further oxygenation. Similarly, the pulmonary artery receives well-oxygenated blood from the left ventricle but returns it to the lungs. Early surgical correction is necessary for survival.

5. Ectopia Cordis: Failure of the anterior thoracic wall to form during development results in the heart being exposed on the surface of the body.

6. Tetralogy of Fallot: This condition involves four simultaneous defects:
(i) Right Ventricular Hypertrophy: Enlargement of the right ventricle.
(ii) Ventricular Septal Defect (VSD): Communication between the two ventricles.
(iii) Overriding Aorta: The aorta originates above the VSD.
(iv) Pulmonary Stenosis: Narrowing of the pulmonary artery entrance, decreasing blood flow and causing right ventricular hypertrophy due to increased preload.

7. Coarctation of the Aorta: Narrowing or partial closure of the aorta after the ductus arteriosus closes, obstructing left ventricular blood flow. The lower body receives less blood than the upper body.

Other Defects:

Mitral Stenosis: Narrowing of the mitral valve slows blood flow.
Left Ventricular Hypoplasia: The left ventricle may be too small to eject a normal cardiac output. Treatment involves surgery.
Left Ventricular Hypertrophy: Enlargement of the left ventricle.
Prostaglandin Treatment: Used to keep the ductus arteriosus open, improving blood flow beyond a coarctation.
Pulmonary Atresia and Tricuspid Atresia: These anomalies prevent effective blood flow from the right ventricle to the pulmonary arteries. Survival depends on a patent ductus arteriosus.
Epstein’s Anomaly: Abnormal tricuspid valve leaflets causing blood regurgitation.

Conclusion: Congenital heart anomalies are often incompatible with life and require immediate attention.

Revision Questions:

Describe the fetal circulation.
Outline five temporary structures of fetal circulation.
Explain the flow of blood in the fetus during intrauterine life.
Describe the changes that occur within the temporary structures during adaptation to extrauterine life.
State three differences between fetal and adult circulation.

Fetal Circulation Read More »

PLACENTA AT TERM

Placenta is a temporary organ of vital communication between the mother and the fetus.

Situation: It is situated in the upper posterior wall of the uterus before the third stage of labour. During the third stage of labour, it separates, descends, and is finally expelled.
Shape: It is a flat, round mass.
Size: It is 18-20 cm in diameter and about 2.5 cm thick around the centre, thinning out towards its edges.

Structure of the Placenta

It is made up of two surfaces:

Maternal surface: Dark red in colour and made up of 18-20 irregular lobes known as cotyledons, each containing masses of chorionic villi. They are divided by deep grooves known as sulci or fissures.
Fetal surface: Whitish-grey and shining in appearance due to the amniotic membranes which cover it. The umbilical cord is inserted in its center, and blood vessels radiate to the periphery like the roots of a tree. These vessels give off branches which reach the cotyledons, thus each has its own supply of fetal blood.

The Fetal Sac

Consists of two membranes:

Amnion membrane: This membrane covers the fetus and contains the fluid in which the fetus lives during pregnancy. It is smooth, tough, shiny, and translucent. It is derived from the inner cell mass; its cells (amniotic cells) secrete amniotic fluid.
Chorion membrane: This is the outer membrane which lies under the decidua capsularis and becomes adherent to the uterine wall. It is thick, rough, opaque, and friable (easily torn). This membrane is derived from the trophoblast. It peels off from the uterus as the placenta separates during the third stage of labor. It sometimes tears, and the pieces may remain inside the uterus; if not expelled in lochia, it may cause sepsis.

THE AMNIOTIC FLUID (LIQUOR AMNII)

Amniotic fluid is a protective liquid contained within the amniotic sac in which the fetus floats.

Amount: Ranges between 500-1500 ml. The amount increases from approximately 30 ml at 10 weeks of gestation to 450 ml at 20 weeks and 800 to 1000 ml at 37 weeks.
Content: It consists of 99% water, various mineral salts, urea (derived from fetal urine), and a trace of proteins (0.25%).
It sometimes contains meconium (fetal rectal waste), vernix caseosa (the white, fatty substance covering the fetus), and hair. It is alkaline due to the presence of phosphates and chloride salts.
Colour: It is a pale straw-coloured fluid and should be odourless and sterile.
Origin: The fluid is produced by amniotic cells/epithelium but is primarily derived from maternal blood. The volume is replaced every 3 hours.
From the beginning of the fifth month, the fetus swallows amniotic fluid (approximately 400 ml daily, about half the total amount).
Fetal urine is added daily from the fifth month onwards, but this urine is mostly water as the placenta handles metabolic waste exchange. The amnio-chorionic membrane forms a hydrostatic wedge that aids in cervical dilation.

Abnormalities of Amniotic Fluid:

Polyhydramnios: An excess of amniotic fluid (1500-2000 ml).
Oligohydramnios: A decreased amount of amniotic fluid (less than 400 ml).

Both conditions are associated with increased incidence of birth defects. Polyhydramnios is associated with anencephaly and esophageal atresia, while oligohydramnios is related to renal agenesis.

Other Abnormalities Associated with Liquor Amnii:

Green-tinged Color: This indicates the presence of meconium and suggests fetal distress. Fetal heart rate should be investigated. Thick meconium during the second stage of labor in breech presentation may not indicate distress; however, in cephalic presentation, it may indicate obstructed labor. This is sometimes seen in rhesus haemolytic disease.

Functions of Amniotic Fluid:

During Pregnancy:

Distends the amniotic sac, allowing free fetal movement.
Acts as a shock absorber, protecting the fetus from injury.
Maintains a constant temperature for the fetus.
Prevents pressure on the umbilical cord.
Prevents adherence of the embryo/fetus to surrounding tissues and prevents limbs from sticking together.
Aids in lung and digestive system development.
Supports muscle and bone development.

During Labor:

Equalizes uterine pressure, preventing interference with placental circulation during contractions.
Forms a bag of membranes that helps dilate the cervix.
Protects the fetus’s head from injury during the first stage of labour.
Washes out the maternal passage with sterile fluid.

FUNCTIONS OF THE PLACENTA (SERPENTE)

Storage: The placenta stores glucose in the form of glycogen and reconverts it to glucose as required. Iron and fat-soluble vitamins are also stored.
Endocrine: Production of hormones: The placenta produces the following hormones:

Human chorionic gonadotropin (HCG): Secreted by trophoblastic cells from the time of implantation for the first two months. Its production falls, and the placenta maintains it at lower levels until term.
Progesterone: By the end of the third month, it is produced in increasing quantity to maintain pregnancy until term.
Estrogenic hormones: Predominantly estriol, which boosts intrauterine growth and development of breasts.
Human placental lactogen: Produced by the syncytium trophoblast and can be measured in maternal blood to assess placental function.
Somatomammotropin: A growth hormone-like substance. Others believed to be produced by the placenta are corticosteroids, adrenocorticotropic hormone, thyroid-stimulating hormone, and oxytocin.

Respiration: The fetus obtains oxygen and gives off carbon dioxide through the placenta. Oxygen is brought to the uterine sinuses by branches of uterine and ovarian arteries; therefore, oxygen from the mother’s haemoglobin passes into the fetal blood by simple diffusion, and carbon dioxide is given off in the same way. The exchanged gases include oxygen, carbon dioxide, and carbon monoxide.
Protection: The placenta acts as a barrier to the passage of most bacteria (e.g., E. coli or bacilli). They do not pass from maternal to fetal blood. However, small organisms such as the spirochete of syphilis and viruses are able to pass through the walls of the chorionic villi. Certain drugs and anaesthetic agents cross to the fetus, and some of them have teratogenic effects. Carbon monoxide from cigarette smoking crosses the placenta and reduces fetal haemoglobin available for oxygen transport.
Excretion: Waste products of metabolism, including carbon dioxide, are excreted into the maternal blood by diffusion and then excreted by the mother.
Nutrition: The fetus obtains its food in the form of nutritive substances from the maternal blood through the placenta. Passage of nutrients such as amino acids, free fatty acids, glucose for energy, iron for blood formation (RBCs), and vitamins occurs.
Transmission of Maternal Antibodies: The fetus gains passive immunity late in the first trimester through maternal immunoglobulin G (IgG), which begins to be transported from mother to fetus at approximately 14 weeks. This can give immunity to the baby during the first few months of life.
Clinical Note: Rhesus antibodies from the mother can pass to the fetus and cause hemolytic disease of the newborn.
Exchange of Electrolytes: Minerals like calcium, potassium, and sodium are exchanged from the maternal blood to the fetus for teeth and bone development.

ABNORMALITIES OF THE PLACENTA

1. Succenturiate Placenta: An accessory lobe of placental tissue is situated within the fetal sac (membranes), with blood vessels connecting it to the main placenta. This results from chorionic villi that failed to atrophy. Retention of this lobe (cotyledon) in the uterus after the main placenta separates can cause postpartum hemorrhage. Midwives should carefully examine the fetal membranes for small holes with placental vessels leading to them, indicating a retained lobe.

2. Circumvallate Placenta: A double fold of amnion and chorion membranes is present. The membranes attach to the fetal surface some distance from the placental edge, appearing as an opaque ring.

3. Bi-partite/Tripartite Placenta: The placenta has two or three complete lobes, with their blood vessels uniting at the umbilical cord.

4. Placenta Accreta: The placenta abnormally adheres to the uterine myometrium.

5. Placenta Increta: The placenta attaches too deeply into the uterine perimetrium.

6. Placenta Percreta: The placenta grows beyond the basal layer and may extend into nearby organs, such as the bladder.

DISEASES OF THE PLACENTA

(a) Infarcts: Red or white patches of dead placental tissue resulting from impaired blood supply. These occur in placentas from mothers with pre-eclampsia, syphilis, post-maturity, or hypertension, often due to fibrin calcification.

(b) Hydatidiform Mole: A trophoblastic disease characterized by excessive, rapid growth of chorionic villi into grape-like structures (hydatidiform mole), resulting in embryo absorption. This can be a benign or malignant mole.

(d) Edema of the Placenta: A large, pale placenta with oozing fluid, associated with hydrops fetalis. This is often due to hemolytic disease of the newborn caused by Rh incompatibility.

FACTORS INFLUENCING PLACENTAL HEALTH IN UTERO

Maternal Age: Advanced maternal age (typically over 35) is associated with increased risks of placental complications like preeclampsia, placental abruption, and growth restriction. This is likely due to age-related changes in the uterine blood vessels and overall maternal health.
Pre-existing Medical Conditions: Conditions like diabetes, autoimmune diseases (e.g., lupus), and chronic kidney disease can significantly impact placental development and function, leading to complications during pregnancy. These conditions often affect blood flow and nutrient delivery to the placenta.
Infection: Infections, especially those occurring during pregnancy, can cause inflammation that damages the placenta. Examples include cytomegalovirus (CMV), toxoplasmosis, and rubella. The resulting inflammation can disrupt placental blood flow and nutrient transport.
Genetic Factors: Genetic variations in both the mother and the fetus can influence placental development and function. These genetic factors can predispose to conditions like placental insufficiency or abnormal placental growth.
Environmental Factors: Exposure to environmental toxins, such as air pollution and certain chemicals, has been linked to adverse placental outcomes. These toxins can disrupt placental development and function, potentially leading to fetal growth restriction or other complications.
Smoking: Reduces blood flow to the placenta, depriving the fetus of oxygen and nutrients.
High Blood Pressure (Hypertension): Damages blood vessels, hindering placental perfusion.
Multiple Pregnancy (Twins, Triplets, etc.): Increased demand on the maternal system can strain placental function.
Maternal Substance Abuse: Drugs and alcohol can directly damage the placenta and interfere with fetal development.
Abdominal Trauma: Physical injury can compromise placental blood supply.
Premature Rupture of Membranes (PROM): Leads to infection and premature delivery, potentially affecting placental function.
Nutrition: Poor nutrition limits nutrient availability for placental development and fetal growth.

EXAMINATION OF THE PLACENTA

The examination of the placenta is done after delivery to identify potential problems and ensure maternal and neonatal well-being. The procedure should be conducted systematically, following these steps:

Aims:

To exclude retained membranes and cotyledons (lobes).
To confirm fetal maturity (though this is better assessed by other means).
To detect abnormalities.
To determine the type of twins (in multiple pregnancies).

Requirements:

Flat surface, adequate lighting.
Measuring jar for estimating blood loss.
Three buckets: one with a red liner for placenta disposal, one with a yellow liner for used gloves, and one with a green or blue liner for instrument decontamination.
Protective gear (gumboots, apron, gloves).
Placenta receiver.
Weighing scale.
Handwashing facilities.

Procedure:

Blood Loss Estimation: Collect all clots and place them in the measuring jar to estimate maternal blood loss.
Membrane Examination: Inspect the membranes for integrity. There should be one opening where the baby passed. Additional openings or vessels indicate retained succenturiate lobes or other abnormalities. Note any vasa praevia (blood vessels running over the membranes).
Fetal Surface Examination:

Clean the cord with a cotton swab to visualize blood vessels.
Examine the cord for the number of blood vessels, their arrangement, length, weight, and any abnormalities.
Peel the amniotic membrane from the fetal surface up to the cord insertion to check chorionic membrane completeness.

4. Maternal Surface Examination:

Hold the placenta in both hands, bringing cotyledons together to identify any missing lobes or abnormalities.
Weigh the placenta (normal weight is approximately 500g, about 1/6th the baby’s weight).
Disinfect the placenta appropriately and dispose of it according to guidelines. Clean the work area thoroughly.
Record all findings in the mother’s chart, noting any abnormalities.

THE UMBILICAL CORD

The umbilical cord connects the placenta to the fetus.

Situation: Between the fetus and the placenta.
Size: 50-60 cm long and 2 cm thick, although length varies considerably.
Shape: Spirally twisted, providing protection from pressure.
Structure: Composed of Wharton’s jelly (a gelatinous substance) covered by the amniotic membrane, protecting three blood vessels: one large vein carrying oxygenated blood to the fetus, and two arteries carrying deoxygenated blood from the fetus to the placenta.

Functions:

Supports and protects the blood vessels;
carries oxygenated blood and nutrients to the fetus;
removes waste products and carbon dioxide from the fetus to the placenta;
acts as a connection between mother and fetus.

ABNORMALITIES OF UMBILICAL CORD INSERTION

1. Velamentous Insertion: The cord inserts into the membranes, with blood vessels traversing the membranes to reach the placenta. If the placenta is in the lower uterine segment, the vessels may lie over the internal os (vasa praevia). Compression of these vessels during labor can cause fetal anoxia; rupture can cause fetal bleeding. Hemoglobin levels should be checked in newborns in suspected cases.

2. Battledore Insertion: The cord inserts at the placental edge. Significant only if the attachment is fragile and prone to rupture.

3. Eccentric/Lateral Insertion: The cord inserts to one side of the placenta; usually insignificant.

ABNORMALITIES OF UMBILICAL CORD LENGTH AND STRUCTURE

Very Short Cord (<35-40 cm): Can cause delayed head descent, difficult delivery, fetal asphyxia, premature placental separation, or cord separation from the placenta.
Very Long Cord (>60 cm): Increased risk of true knots, nuchal cords (entanglement around the fetal neck), cord prolapse, and compression of umbilical vessels leading to anoxia.
False Knots: Blood vessels looping within Wharton’s jelly; insignificant.
True Knots: The cord is tied in a knot; the fetus passes through a loop of the cord. Tightening during delivery can cause anoxia and stillbirth.
Very Thick/Thin Cord: Requires careful cord clamping to prevent hemorrhage.
Omphalocele: Rare protrusion of fetal intestines into the umbilical cord, often suspected if the cord is swollen near the umbilicus. This is a serious congenital abnormality requiring surgical repair. It’s a type of abdominal wall defect where the intestines (and sometimes other organs) protrude through the umbilical cord. The sac covering the protruding organs is usually transparent and contains amniotic fluid.

7. Abnormal Number of Blood Vessels:

Two Vessels: One umbilical artery is missing. This is associated with congenital internal abnormalities, especially renal agenesis (absence of one or both kidneys) and increased risk of cardiovascular defects.
One Vessel: Extremely rare, associated with serious cardiac and other vascular defects. This is a significant finding requiring careful monitoring and follow-up.

CLEANING OF THE BABY’S UMBILICAL CORD

Objectives:

Prepare the necessary supplies for cord cleaning.
Clean the cord systematically.

Trolley

Top shelf	Bottom shelf	At the side
Sterile park containing;	Normal saline.	Hand washing equipment.
2 Galipots.	Drum with cotton.
Sterile hand towel and draper.	Swabs.	Screen.
Cord ligatures.	Cheatle forceps.
2 Receivers.	Baby’s clothes.
Sterile gloves.	Gloves.
Sterile plastic cord clamps.	Plastic apron.
Cord scissors.

Procedure

Step	Action	Rationale
1.	Apply soft skills when explaining the procedure to the mother.	To facilitate cooperation.
2.	Position the baby, expose the cord stump only and keep the baby warm.	To prevent hypothermia and for accessibility of the cord.
3.	Put on sterile gloves.	To prevent spread of Infections.
4.	Show the mother how to clean the cord herself.	To empower her to do it.
5.	Inspect the cord clean the cord as follows; Hold the cord with the swab, clean base of the cord in single circular movement using a swab dipped in normal saline once and discard.	To detect any infection and bleeding.
6.	Clean the cord from the base upwards with a swab once until the cord is clean.	To detect any infection and bleeding
7.	Dry the cord	To prevent growth of microorganisms.
8.	Cover the baby and thank the mother.	To prevent hypothermia, motivate.
9.	Record findings	Recording for her continuity of care.

Points to Remember:

Clean the cord every day until it separates and heals.
Clean the cord with saline water 2–3 times a day.
Keep diapers/nappies below the umbilicus.
Examine the cord stump daily for any bleeding, infection, and separation.
If there are any signs of infection (e.g., reddening of the surrounding skin), report or refer.

Complications of Improper Cord Care:

Bleeding
Infections (e.g., omphalitis)
Anaemia
Delayed separation

Revision Questions:

Describe the fetal surface of the placenta.
Describe the maternal surface of the placenta.
Describe the placenta at term.
Outline eight functions of the placenta.
Explain four abnormalities of the placenta.
List two dangers of placenta succenturiate.
Give five abnormalities of the umbilical cord.
List three implications of a missing umbilical blood vessel.

VERNIX CASEOSA

A white, sticky, slippery subcutaneous fat found on the baby’s skin.

Quantity: Depends on the amniotic fluid temperature; premature babies may have a larger quantity. It gradually diminishes, and mothers should be advised not to rub it off the baby.

Functions:

Allows the baby to move freely without limbs sticking together.
Keeps the baby warm.

Revision Questions

What is amniotic fluid?
State two abnormalities of amniotic fluid.
Outline four functions of amniotic fluid during labor.
Give two importances of vernix caseosa.
State three differences between amnion and chorion membranes.

Placenta at Term Read More »

EMBRYOLOGY

Embryology is the study of embryo development. This includes the developmental process of a single-cell embryo to a baby.

Embryogenesis is the process by which an embryo develops into a foetus.

It begins when an ovum and sperm meet and fertilization(the union of the male gamete (sperm) and the female gamete (oocyte) to form a zygote.
The fertilization results in the formation of a zygote.
The zygote undergoes rapid division, developing into a morula, then a blastocyst, an embryo, and finally a fetus.

The entire process culminates in childbirth after approximately nine months.

FERTILIZATION

Fertilization is the fusion of male and female gametes. The process involves several stages:

1. VAGINA

During intercourse, approximately 400,000,000 spermatozoa are deposited into the vagina. They swim through the vaginal mucosa, but its acidic environment eliminates many; only the strongest survive. Some are unable to penetrate the cervical mucosa.

2. CERVIX

Spermatozoa surviving the vaginal acidity enter and traverse the cervix, aided by the arbor vitae and cervical crypts, which prevent them from flowing back into the vagina. They then move through the uterus and into the fallopian tubes. This journey takes 2 to 7 hours.

3. FALLOPIAN TUBES

Movement slows due to ciliary action and peristaltic movements of the tube. Fertilization occurs in the ampullary region of the uterine tube, its widest part, located near the ovary. Spermatozoa can remain viable in the female reproductive tract for three days but cannot immediately fertilize the oocyte. They undergo changes:

Capacitation: This involves the removal of a glycoprotein coat and seminal plasma proteins from the acrosomal region of the spermatozoon head, enhancing flagellar movement. The ruptured acrosome releases hyaluronidase, an enzyme that erodes the ovum’s wall, allowing the sperm head to enter. The ovum then secretes a substance sealing its cell membrane, preventing other sperm penetration. This process lasts approximately 7 hours in humans. The sperm’s body and tail detach and are absorbed.
Acrosome Reaction: Acrosin and trypsin-like substances are released to penetrate the zona pellucida and corona radiata. The zona pellucida, a glycoprotein shell surrounding the ovum, facilitates sperm binding and induces the acrosome reaction.
Fusion of oocyte and sperm cell membranes and pronuclei: A zygote is formed, receiving glycogen nourishment from the uterine goblet cells.

CHROMOSOMES

Fertilization restores the diploid chromosome number. The zygote contains 46 chromosomes: 23 from the father and 23 from the mother. One chromosome from each parent is a sex chromosome, determining the baby’s sex. An X-carrying sperm produces a female (XX) embryo, and a Y-carrying sperm produces a male (XY) embryo. Sex is determined at fertilization.

First Week of Development (Pre-embryonic)

The first week involves the formation of a zygote, morula, and blastocyst. Ciliary action in the fallopian tube transports the zygote towards the uterus (3 days after fertilization or 7 days after ovulation). Mitotic divisions increase cell number (2, 4, 8, 16, called blastomeres). Around day 4, compaction forms a cell mass called a morula.

Clinical Note: Cell differentiation begins, determining which cells will form specific organs; injury at this stage can result in limb or organ loss.

Second Week of Development

During the second week of development, the blastocyst forms the decidua, becomes embedded in the endometrium, and begins forming the placenta. As the blastocyst embeds in the endometrium, the trophoblast differentiates into two layers:

the syncytiotrophoblast and the cytotrophoblast.

The inner cell mass also begins to develop, and changes occur in the endometrium as it prepares to support the growing embryo.

The endometrium is now called the decidua and no longer sheds. The decidua thickens, and its middle layer becomes vascular and edematous. The glands in the decidua secrete nutrients such as glycogen to nourish the embryo.

Clinical Note: hCG, produced by the syncytiotrophoblast, is detectable in urine via medical pregnancy tests within the second week of gestation

Divisions of the Decidua

The decidua is divided into three parts:

Decidua Basalis – The part of the decidua that lies between the blastocyst and the myometrium.
Decidua Parietalis – The compact layer that covers the blastocyst and separates it from the uterine cavity.
Decidua Vera/Capisularis – The true decidua, which is the modified mucosal lining of the uterus.

Clinical note: Decidua reaction and implantation may lead to bleeding due to increased blood with lacunae spaces and rupture of capillaries. This occurs around the 13th day after fertilisation; bleeding lasts 1 to 2 days may be confused with normal menstruation and thus confuses marking the date of conception. It is called implantation bleeding.

Placentation (Formation of the Placenta)

During embedment, the trophoblast and inner cell mass continue to grow and differentiate. The trophoblastic cells form three layers: Syncytiotrophoblast, Cytotrophoblast and Mesoderm.

These layers form finger-like projections called villi, which invade the decidua and blood vessels. By 12 weeks, the villi disappear, and the chorionic membrane is formed. The placenta is fully developed by this time and takes over the production of progesterone from the corpus luteum.

Embryonic Period (3rd to 8th Week)

This phase is known as the period of organ formation or organogenesis. It starts from the third week and continues until the eighth week of development. During this time, the main organ systems of the body are established.

1. Formation of Three Germ Layers:

The cells of the embryoblast (inner cell mass) differentiate into two layers: the epiblast and hypoblast, forming the bilaminar embryonic disc.
Through a process called gastrulation, these layers form three primary germ layers: ectoderm, mesoderm, and endoderm, each giving rise to specific organs and tissues.

2. Amniotic and Yolk Sacs:

The amniotic sac is lined by ectoderm cells, and the yolk sac is lined by endoderm cells. Between these two cavities lies mesoderm cells. The developing fetus is formed from the embryonic plate, which is made up of endoderm cells.

Derivatives of the Germ Layers

1. Ectodermal Germ Layer: The ectoderm forms important parts of the nervous system and skin. Its derivatives include:

Central and peripheral nervous systems
Sensory organs (eyes, nose, ears)
Epidermis (skin), hair, nails
Glands such as mammary and subcutaneous glands
Tooth enamel

2. Mesodermal Germ Layer: The mesoderm forms bones, muscles, blood vessels, and connective tissues. Key derivatives include:

Cranial and spinal bones (vertebrae)
Muscles and connective tissue
Blood vessels and blood cells
Lymphatic system, kidneys, and reproductive organs
Serous membranes (lining of body cavities like pleura, peritoneum, and pericardium)

3. Endodermal Germ Layer: The endoderm primarily forms the lining of internal organs. Key derivatives include:

Gastrointestinal tract (GIT)
Epithelial lining of the respiratory system
Liver, pancreas, thyroid, and parathyroid glands
Lining of the urinary bladder and urethra
Parts of the auditory system (middle ear and auditory tube)

Clinical Notes

Most major organs develop between the third and eighth weeks. Exposure to harmful substances, like smoking or alcohol, during this period can cause birth defects.
Abortions during this stage result in the loss of a human life, stressing the importance of careful consideration.

Amniotic Cavity/Sac

The amniotic sac fills with fluid (amniotic fluid) over time, allowing the fetus to float and move freely. By the time of full formation, the fetus is suspended in this fluid inside the sac, providing a protective environment.

Body Stalk and Yolk Sac

The body stalk connects the trophoblast to the inner cell mass and eventually forms the umbilical cord, which carries blood between the fetus and placenta. Part of the yolk sac becomes the digestive tract, while the rest disappears into the umbilical cord, forming a structure known as the vitelline duct. By the end of this process, the fetus is floating in amniotic fluid, connected to the placenta by the umbilical cord, and surrounded by two membranes: the amnion (inner) and the chorion (outer).

Fetal Period (9th Week to Birth)

The fetal period begins at the start of the ninth week and continues until birth. During this time, the following key developments occur:

Organ and Tissue Development: The organs and tissues that began forming during the embryonic period continue to mature and develop further.
Rapid Growth: There is a significant increase in the fetus’s size, including both weight and height.
Placenta Functionality: The placenta becomes fully developed and plays a critical role in nourishing the fetus and supporting its growth.
Duration of Pregnancy: A full-term pregnancy is typically 280 days (about 40 weeks) from the first day of the last menstrual period.

Parturition (Birth)

The exact signals that initiate labor are not fully understood. However, preparations for labor usually begin between 34 and 38 weeks. This is influenced by:

A decrease in progesterone levels
An increase in prolactin
A reduced withdrawal of prostaglandins, which helps soften the cervix and prepare the uterus for labor.

Revision Questions:

Define fertilization.
Describe the events in the vagina, cervix, fallopian tube, and uterus in the early stages of development.
Explain the characteristics that determine an individual’s traits.
Define capacitation.
Discuss the causes of implantation bleeding.
List the layers involved in the formation of the placenta.
Explain how the fetus develops.
Describe the development of the placenta.
Define nidation.
Outline the layers of the decidua.
Describe the formation of the decidua.
Explain the changes in the first week of development.
Describe the activities of the second week of development.
Summarize the embryonic period.
Explain the derivatives of the endodermal germ layer.
Outline the derivatives of the ectodermal germ layer.
List the derivatives of the mesodermal germ layer.
Define neurulation.
Describe the fetal period.
Define parturition.

Fertilization and Embryology Read More »

THE MENSTRUAL CYCLE

The menstrual cycle is a sequence of events that occurs every 21-36 days in females after puberty, continuing throughout the childbearing years.

Factors that Influence the Menstrual Cycle

For a normal menstrual cycle to occur, the following components must be functioning properly:

The Hypothalamus: Stimulates the release of luteinizing hormone-releasing hormone (LHRH), which triggers the pituitary gland.
The Pituitary Gland: Secretes hormones that stimulate the ovaries.
The Ovaries: Produce hormones that trigger changes in the uterus and the growth of the ovum.
The Uterus: Experiences changes, shedding the endometrium regularly.
The Vagina: Acts as a passageway for menstrual flow.
Hormones: Key players in regulating the menstrual cycle and causing various changes.

Hormones Involved in the Menstrual Cycle

(a) Gonadotrophic Hormones: The hypothalamus, part of the diencephalon located in front of the thalamus, secretes gonadotropin-releasing hormone (GnRH), which stimulates the anterior pituitary gland to release follicle-stimulating hormone (FSH).

Functions of FSH:

Promotes the maturation of ovarian follicles (Graafian follicles), usually one at a time, and triggers estrogen secretion, leading to ovulation.
The developing follicle secretes estrogen, causing the uterus to proliferate and the breasts to enlarge, preparing for breastfeeding.
About 24-36 hours before ovulation, the anterior pituitary gland secretes luteinizing hormone (LH), causing the Graafian follicle to rupture, leading to ovulation and the formation of the corpus luteum.
The corpus luteum secretes progesterone, which thickens the endometrium and maintains pregnancy.

Note:

If fertilization doesn’t occur, progesterone withdrawal happens.
The corpus luteum degenerates into the corpus albicans (a white body) and finally becomes fibrous.
The cycle then begins again due to stimulation by the hypothalamus.

(b) Ovarian Hormones.

1. Oestrogen:

Produced by growing follicles (granulosa cells and theca).
Responsible for the development of female secondary sexual characteristics (e.g., breast growth).
Causes proliferation of the endometrium, prepares the vagina, and promotes the production of cervical mucus.

2. Progesterone:

After ovulation, LH stimulates the corpus luteum to produce high levels of progesterone and low levels of estrogen.
Progesterone causes the endometrium to become more tortuous, raises basal body temperature, and induces sensations of fullness in the breasts before menstruation.
The rise in ovarian hormones decreases the flow of GnRH, leading to reduced production of FSH and LH. This is a negative feedback loop.
A positive feedback mechanism occurs when blood estrogen levels rise, stimulating the hypothalamus to secrete more luteinizing hormone-releasing factor.

Uterine Phases/Events of the Menstrual or Endometrial Cycle

1. Menstrual Phase.

If the ovum is not fertilized, the corpus luteum degenerates, causing progesterone and estrogen levels to fall.
The functional layer of the endometrium, which relies on high levels of ovarian hormones, is shed during menstruation.
High circulating levels of progesterone and estrogen inhibit FSH and LH production in the anterior pituitary gland. If pregnancy occurs, these hormones prevent the release of another ovum.
When the corpus luteum degenerates, falling hormone levels cause the anterior pituitary to resume FSH secretion, initiating the next cycle.

2. Proliferative Phase

This phase begins immediately after the menstrual phase and lasts until ovulation. It coincides with the follicular phase.
The endometrium regenerates, forming a new layer.
This phase typically lasts 10 days in a 28-day cycle:

Early proliferative phase: Occurs 4-7 days after menstruation.
Mid proliferative phase: Occurs 8-10 days after menstruation.
Late proliferative phase: Occurs 11-14 days after menstruation.

FSH stimulates the growth and maturation of Graafian follicles, which produce estrogen to repair the endometrium.
The endometrium thickens, consisting of three layers:

Basal layer: Next to the myometrium, not shed during menstruation, as it contains the necessary structures to rebuild the endometrium.
Functional layer: Spongy, tubular glands, about 2.5 cm thick.
Compact layer: Cuboidal ciliated epithelium.

Note: The functional and compact layers (b and c) are shed during menstruation.

3. Secretory Phase

This phase follows the proliferative phase and is regulated by progesterone.
The endometrium becomes edematous (thickens and swells) and develops a spongy appearance.
Secretory glands produce increased amounts of glycogen to nourish a potential fertilized ovum.
This phase lasts for about 14 days.

Note:

If the ovum is not fertilized, menstruation begins, marking the start of a new cycle.
If the ovum is fertilized, the zygote travels to the uterus and becomes embedded in the endometrium, producing human chorionic gonadotropin (HCG). This hormone supports the corpus luteum, ensuring continuous secretion of progesterone and estrogen to maintain pregnancy.
After about 12 weeks, the placenta forms and takes over hormone production (estrogen, progesterone, and gonadotropins) to sustain the pregnancy.

Gametogenesis

Gametogenesis is the developmental process that leads to the creation of reproductive cells.

Before fertilisation, gametes have to be formed in the process of gametogenesis which takes place on the principles of meiosis.

Production of a Mature Ovum (Oogenesis)

Oogenesis is accomplished through meiosis, a process beginning during embryonic development.

A primary oocyte produces one secondary oocyte and a polar body.
The secondary oocyte and the first polar body then give rise to a mature ovum and three polar bodies, which degenerate. The ovum is the largest cell in the body.

Spermatogenesis (Production of Sperm)

Spermatogenesis, the formation of spermatozoa, begins at puberty (around 14-16 years). Sperms are produced in the basal layer of the germinal epithelium of the testes under the influence of Follicle-Stimulating Hormone (FSH). This occurs through meiotic cell division.

Primitive structures (spermatogonia) in the testes are nourished by Sertoli cells, developing into primary spermatocytes. These primary spermatocytes, possessing a diploid number of chromosomes, undergo meiosis to form two daughter cells: secondary spermatocytes.
The Luteinizing Hormone (LH) acts on the secondary spermatocytes, initiating the second meiotic division and forming spermatids. The larger portion of the spermatid develops into a spermatozoon (sperm). This transformation of spermatids into spermatozoa is called spermiogenesis.

The spermatozoon has three main parts:

Head: Contains the acrosome (with the hyaluronidase enzyme, which breaks down the ovum’s outer layer for sperm entry) and the nucleus (containing chromosomes and genetic material).
Body (Midpiece): Provides nutrients for the sperm.
Tail (Flagellum): Propels the sperm after ejaculation.

Male Hormones:

The hypothalamus produces gonadotropin-releasing factor (GnRH), which stimulates the anterior pituitary gland.
FSH acts on the seminiferous tubules to stimulate spermatozoa production.
LH stimulates interstitial cells to produce testosterone, the primary male sex hormone responsible for the development of secondary sexual characteristics in boys at puberty, including:

Increased muscle growth and height/weight gain.
Enlargement of the larynx (deeper voice).
Growth of hair on the face, armpits, chest, abdomen, and pubic area.
Enlargement of the penis, scrotum, and prostate gland

Revision Questions:

Define meiosis.
Describe the formation of a mature ovum.
State the differences between a primary and a secondary oocyte.
What is spermiogenesis?
State two functions of the testes.
Describe the male reproductive system.
List three hormones that influence spermatogenesis.
List three hormones involved in male reproduction.

Menstruation Cycle Read More »

THE FEMALE BREAST (MAMMARY GLAND)

Breasts are two accessory glands of the female reproductive system.

Situation: They are situated on the anterior chest wall over the pectoralis major muscles between the 2nd and 6th rib and each extend from the sternum to the axilla forming the axillary tail. It’s stabilized by the suspensory ligament.

Shape:

In a prime gravida, the shape is hemispherical and has a tail tissue extending towards the axilla forming the axillary tail.
It is flat and pendulous or pawpaw shaped in the multiparous women.
This varies with each individual and the stage of development as well as age.

Development: The nipples are present at birth but no further development takes place till puberty when the breast increases in size. Further development takes place during pregnancy, but it reaches its full maturity during lactation.

Gross Structure:

The breast has the following parts:

Axillary Tail: This is a tail of tissue called the axillary tail of Spence, extending from the breast towards the axilla.
Areola: It extends 2.5cm around the nipple and it contains sebaceous glands which become more visible in pregnancy and they are known as Montgomery tubercles. These lubricate the nipple.
The Nipple: It lies in the centre of the areolar at the level of the fourth rib. It is a protuberance about 6mm in length, composed of erectile tissue and is covered with epithelium, contains plain muscle fibres which have a sphincter-like action controlling the flow of milk. The surface of the nipple is perforated by small orifices which open in the lactiferous ducts.

Microscopic Structure:

It is composed largely of glandular tissue but also of some fatty tissue and is covered with skin. The glandular tissue is covered with connective tissue. They are 18-20 in number.

The internal structure is said to be composed of the following:

Nipple: This is located at the apex of the breast and projects up to 1 cm.
Areola: This is a roughly circular area of skin that surrounds the nipple. Its colour darkens during pregnancy due to the deposition of melanin. The areolar skin contains Montgomery glands which secrete a protective oily lubricant.
The Lobes: These separate the different batches of alveoli.
The Alveoli: Each gland is called alveolus and is the milk-secreting unit lined by milk-making cells called acini cells. These are covered by myo-epithelium which contract to expel milk.
The Lactiferous Tubule: Is also known as small ducts, they extend from the alveoli running into one another uniting to form bigger ducts which run into lactiferous ducts.
The Lactiferous Duct: This is the central duct into which small ducts or tubules run.
The Ampulla or Lactiferous Sinus: This is a widened out portion underneath the areola. It is a continuation of the lactiferous duct towards the nipple and terminates as minute openings on its surface. The ampulla is a milk reservoir during breastfeeding.

Blood Supply:

By internal and external mammary arteries.
Intercostal arteries which originate from the aorta.

Venous Return: From a circular network around the nipple and drain into internal mammary and axillary veins.

Lymphatic Drainage: Lymph drains freely between the breasts and into lymph nodes in the axilla and the medial sternum.

Nerve Supply: There is poor nervous supply. The skin is supplied by branches of the 4th, 5th and 6th thoracic nerves. The functions of the breasts are controlled by hormones i.e., oestrogen, progesterone, and prolactin. The breast is supported by the suspensory ligaments.

Functions of the Breast:

To supply milk to the baby.
To give shape to the female figure.
It is a secondary sex organ.

Physiology of the Breast

1. Before Pregnancy

Breasts are present at birth. They develop at puberty due to the effect of oestrogen, which passes from the growing ovarian follicle through the bloodstream to the breast.

Effects of Oestrogen on the Breast:

The breasts enlarge and assume the adult female size and shape.
It causes further growth of the nipple and areola.
It promotes growth and development of the lactiferous tubules and ducts. Therefore, breast enlargement is due to the enlargement of the ducts.

Before menstruation, breast fullness and tingling occur due to progesterone stimulation from the corpus luteum.

2. During Pregnancy

Further breast development and enlargement occur due to alveoli hypertrophy. This is due to progesterone stimulation in preparation for milk production.
Progesterone and oestrogen play an important part in the development of glandular tissue and its ducts.

3. After Delivery

Prolactin is responsible for milk production, beginning around the third day postpartum. This occurs after oestrogen is fully withdrawn, and the breasts reach their full development.

Factors Affecting Lactation:

Hormonal Control: Placental separation and expulsion alter the oestrogen-progesterone balance, resulting in prolactin release from the anterior pituitary gland.
Physical Factors: The neuro-hormonal reflex, involving oxytocin, causes milk letdown when the baby suckles.
Emotional Factors: Maternal willingness to breastfeed and the baby’s ability to breastfeed facilitate milk production.
Nutritional Factors: Well-nourished lactating women experience more successful breastfeeding.

Physiology of Lactation

1. Hormonal Control:

An alteration in the progesterone-oestrogen balance results in prolactin release from the lactotrophs of the anterior pituitary gland.
Clinical Note: To suppress lactation (e.g., after baby loss), oestrogen may be administered via drugs like doxinex, cabergoline, etc., which inhibit prolactin.

2. Milk Production:

Essential substances are extracted from the increased blood supply to the breast for milk formation. Fatty globules and protein molecules form at the base of acini cells, move into the alveoli, and travel through the lactiferous tubules. Lactation depends not only on hormones but also on breast blood supply.

3. Passage of Milk:

Milk transit from secretory cells to the nipple is aided by:

Back Pressure: Newly formed globules push preceding ones into the lactiferous tubules and ducts.
Neuro-Hormonal Reflex: Suckling empties the ampulla, causing large lactiferous ducts to contract and force milk towards the nipple. Nipple