Anatomy

uterus, fallopian tube, ovaries midwives revision

THE NON-PREGNANT UTERUS

The uterus is a hollow muscular organ of the female reproductive system where offspring gestate.
A pear-shaped organ, the uterus lies posterior-superior to the bladder and anterior to the rectum in the female pelvis. It consists of the fundus (top), body (middle), and cervix (lower). The uterus is composed of the endometrium (inner mucosal lining), myometrium (smooth muscular middle layer), and perimetrium.

Situation: The uterus lies in the true pelvis in an anteverted (leans forward) and ante-flexed (bends over its body) position. The body of the uterus lies above the urinary bladder.

Shape – it resembles that of an avocado or it is pear shaped.

Size – 7.5cm long, 5cm wide and 2.5cm thick.

Weight – 60 grams.

Gross-structure:

The uterus consists of two main parts; the body or corpus and the neck or cervix.

1. THE BODY OR CORPUS
Forms the upper 2/3 of the uterus and it is the whole part above the cervix.

The Fundus: This is the portion of the body which lies between and above the cornua.
NOTE: This is the part a midwife palpates during abdominal examination to measure the height of the uterus/fundus during pregnancy and fundal height during puerperium.
The cornua: These are the lateral angles of the uterine body where the fallopian tubes are attached. In normal labour, the uterine contractions start at the cornua and spread downwards the uterus.
The cavity: This is the potential space between the posterior and anterior walls. It is triangular in shape and it is occupied by the products of conception during pregnancy, mainly the fetus and the placenta.
The isthmus: Is the narrowest part of the body of the uterus immediately above the internal os. During pregnancy, this develops into the lower uterine segment.

2. THE NECK OF THE UTERUS
This forms the lower 1/3 of the uterus and enters the vagina at right angles.

Microscopic structure of the uterus
There are three layers of tissue from within.

1. The endometrium: It is the mucus membrane which lines the cavity of the uterus. It is made up of three layers; The compact layer, the Functional (spongy) layer and the Basal layer. The appearance of this lining varies with each day of the menstruation cycle. During menstruation, it is shed up to the basal layer.

2. The myometrium: It is the thickest muscle layer and has three layers.

Outer layer or longitudinal fibres — These pass over the fundus from front to back, starting and finishing at the level of the internal os with a few fibres into the cervix. In labour as the muscles contract and relax, they help to shorten the upper uterine segment and help to pull up and shorten the cervix.
The middle layer — Oblique fibres
These are the interlacing fibres. They are known as living ligatures. They close the bleeding blood vessels after the separation of the placenta and so control bleeding.
The circular muscle fibres — Found in the cervix and cornua. Help in dilatation of the cervix. They relax during labour as they are more in the cervix.

3. The perimetrium – This is the outer covering of the peritoneum which covers the uterus except at the side where it forms the broad ligaments and at the level of the isthmus.

Relations to the uterus

Superiorly: The intestines and the abdominal muscles.
Anteriorly: The bladder, Uterovesical pouch, anterior vaginal fornix.
Posteriorly: The rectal uterine pouch, rectum, utero-sacral ligaments.
Laterally: The broad ligaments, ureters, Fallopian tubes, ovaries and round ligaments.
Inferiorly: The vagina.

Blood supply: Uterine arteries: These arise from the internal iliac arteries and ovarian arteries.
Venous return: Uterine veins.
Lymphatic drainage: Into the internal iliac and sacral glands.
Nerve supply: By the sympathetic and the parasympathetic nerves which are branches of the lee Franken Hauser plexus.

Supports

The round ligaments: Maintain the uterus in its position of anteverted and anteflexed. They extend from the cornua at each side, pass downwards and insert into the tissue of the labia majora.
The broad ligaments: These are not true ligaments but folds of peritoneum extending laterally between the uterus and the side walls of the pelvis.
Cardinal ligament or Transverse cervical ligaments: They run out from the side walls of the cervix to the side walls of the pelvis.
The uterosacral ligament: These pass from the cervix to the sacrum.
Pub cervical ligament: These pass from the cervix under the bladder to the pubic bone.
The ovarian ligament: These begin at the cornua and attach to the ovaries.

Functions of the Uterus:

Responsible for menstruation as the endometrium sheds during each monthly period.
The endometrial cavity accommodates the fetus during pregnancy.
Uterine muscles facilitate contractions during labor, enabling the expulsion of the infant through the birth canal.
To accommodate and nourish the fertilized ovum for the gestation period.
To involute following childbirth.
It is a site for intra-Uterine Device insertion.

Clinical note

The uterus undergoes physiological changes in structure when one is pregnant due to the action of progesterone and oestrogen hormone.

Guiding questions

Describe the non-pregnant uterus with a well-labeled diagram.
List three layers of the uterus.
Describe the myometrium of the uterus.
Outline three uterine supports.
Outline four functions of the uterus.

Clinical procedure: Antenatal Examination

An antenatal mother is waiting to be examined. Using the Leopold method, palpate her abdomen.

TASK: Abdominal examination

Step	Action:	Rationale:
1.	Welcome and explain the procedure to the mother, wash hands.	To allay anxiety and promote cooperation.
2.	Request mother to empty bladder.	For comfort.
3.	Put the mother in a recumbent position and expose the xiphisternum and symphysis pubis.	To aid relaxation of the abdominal muscles.
4.	While standing at the foot of the bed, inspect and observe the abdomen for: – Striae gravidarum, linear nigra, Fetal movements, Size and shape – Linea alba, – Skin rashes, skin hyper-pigmented spots and scars	To rule out pregnancy.
5.	Stand on the right hand side of the mother, – Ask the woman if she has any pain palpation in the abdomen. – Do light palpation of her left and right abdomen, and ensure to exclude enlargement of the spleen and liver.	To detect anatomical conditions of the organs.
6.	Fundal grip. Palpate the upper abdomen with both hands to feel the gravid uterus.	To detect the size and position of the uterus.
7.	Umbilical grip. Place the hand to apply deep pressure with the palm on the lateral sides to feel the uterus. Take note of the irregular nodules which indicate fetal limbs.	To identify the location and position of the fetal back.
8.	Pawlik’s grip – Turn and face the mother’s legs. – Use the fingers and thumbs to feel the moving fetal limbs in the lower abdomen.	To determine the presentation and the amniotic fluid volume.
9.	Pelvic grip. Move the finger towards the pelvis to determine where the brow is located.	To confirm presentation and the lie.
10.	Auscultation Place Pinard’s stethoscope over the maternal abdomen where the fetal back was felt. Move the stethoscope until maximum intensity is felt. Place the right hand on the maternal radial pulse and compare it with the fetal heart rate. Count the fetal heart beats per minute.	To determine fetal viability.
11.	Tell the mother findings

Fallopian Tubes

Fallopian tubes are two muscular tubes leading from the ovaries to the uterus.

They consist of the infundibulum (with fimbriae near the ovary), ampullary region, isthmus (narrowest part linking to the uterus), and interstitial part traversing the uterine musculature. They are also called oviduct or fallopian tubes named after Fallopius, an ancient Greek anatomist.

Situation

They are situated in the true pelvis on either side of the uterus.
Each tube extends from the cornua of the uterus and travels towards the side walls of the pelvis, then turns downwards and backwards before reaching it.
The tubes lie in the broad ligaments.

Shape

They are tubes. The lumen of each communicates with the cavity of the uterus superiorly and the peritoneal cavity inferiorly.

Size

The length of each tube is approximately 10 cm.
The lumen is about 3mm.
The thickness is that of an ordinary pencil.

Gross Structure/Surface Anatomy

Each tube is divided into four parts namely;

1. The interstitial portion/intramural.
a. This lies within the walls of the uterus.
b. It is 1.25cm thick.
c. Its lumen is about 1mm in diameter.

2. The isthmus.
Is the narrow part immediately adjoining the uterus. It is 2.5cm long.

3. The ampulla.
Is a widened area of the tube where fertilization is thought to occur. It is 5cm long.

4. The infundibulum.
a. It is the funnel-shaped extremity.
b. It is the terminal portion of the tubes, which turns backwards and downwards.
c. It extends in finger-like processes which surround the orifice of the tube.
d. It measures 1.25cm long.

Microscopic Structure

The fallopian tube has 4 coats (from within outwards):

A lining of ciliated columnar epithelium.
a. This forms the lining of the tube and aids the passage of the ovum to the uterus.
b. This epithelium is arranged in folds known as placae which slows down the journey of the fertilized ovum and so making it ready for embedding when it reaches the uterus.
A layer of connective tissue:
Lies beneath the epithelium.
Muscle coat/Muscularis.
This is a thin muscular coat arranged in two layers:
a. Inner layer of circular fibres, which are numerous, near the infundibulum.
b. Outer layer of longitudinal fibres.
Peritoneum: A covering of the peritoneum of the broad ligament.
hangs over the tubes but absent on their inferior surface.

Blood Supply

The blood comes from the uterine and ovarian arteries.
The venous return is by corresponding veins.

Lymphatic Drainage: The lymphatic drainage is into the lumbar glands.

Nerve Supply: From the ovarian plexus.

Supports: The Infundibulo-pelvic ligaments. These are formed from folds of the broad ligament and run from the infundibulum of the tube to the side walls of the pelvis.

FUNCTIONS

The tube forms a canal through which the ovum and sperm pass.
Provide a site for fertilization (ampulla) and guide the zygote to the uterus for implantation.
Commencements of early development of the fertilized ovum take place in the tube.
Female sterilization is hence a Family Planning site.
Facilitate sperm movement using tubal cilia and transport the ovum from the ovaries to the uterus.
Supply nutrients to the fertilized ovum during its journey to the uterus.

Relations

Anteriorly: Intestines and the peritoneal cavity.
Posteriorly: The peritoneal cavity and the intestines.
Superiorly: Peritoneal cavity.
Inferiorly: The broad ligaments and the ….
Laterally: Infundibulo-pelvic ligaments and the side walls of the pelvis.
Medial: The uterus.

Clinical note

Conditions like ectopic pregnancy and Salpingitis are associated with the fallopian tubes.

Important

Cleanliness of the vulva is very significant.
Early detection of abnormal vaginal discharge like the pus discharge of Gonorrhea is important so that treatment is given on time.

Revision Questions

List four parts of the uterine tubes.
Outline two functions of the ampulla.
Describe the uterine tubes with the aid of a diagram.
Explain three functions of the uterine tubes.

Ovaries:

The ovaries are two small glandular structures. They are the female sex endocrine glands in which ova are produced.

Two glands on each side of the uterus, ovaries are attached to the uterus by the ovarian ligament and the pelvic wall by the suspensory ligament. Covered by the mesovarium (part of the broad ligament), the ovary’s size varies with age and menstrual cycle stage.

Situation

a. They lie within the peritoneal cavity in a small depression of the posterior wall of the broad ligaments.

b. They are situated at the fimbriated end of the uterine tubes, about the level of the pelvic brim.

c. Each is attached to the upper part of the uterus by the ligament of the ovary and the tissue called Mesovarium, a band of the broad ligament.

Shape: They are small, with a corrugated surface, like an organ, dull white in colour.

Size: The size of ovaries varies in age and in different individuals. They are about 2.5cm-3.5 cm long, 2cm wide and 1cm thick.

Development: The ovaries develop in the germinal ridges of the posterior wall and during fetal life, they descend into the pelvic cavity in the same manner as the testes.

Gross Structure/Surface Anatomy

The structure of the ovaries varies with the age of the woman.

From birth to puberty: The organs are smooth, dull white and solid in consistency.
Menstrual phase: Between puberty and menopause, the organs are larger and irregular on the surface, more like a walnut than an almond.
Post-menopausal phase: The ovaries become smaller and shrunken and are covered with scar tissue where month after month, the Graffian follicles have ruptured.

Microscopic Structure

The ovaries have two layers of tissue or zones:

The Medulla.

This is the central portion, consisting chiefly of fibrous tissue, blood vessels, lymphatics and nerves.
Has the hilum which is the central point of entry for blood vessels, lymphatics and nerves.
Contains no follicular structures but in pregnancy, the corpus luteum may spread towards the medulla.

The cortex.

This is the functional part of the ovary, because it’s where Graffian follicles grow.
It surrounds the medulla.
It consists mostly of stroma in which the Graffian follicles are embedded.
Before puberty, the ovaries are inactive, but the stroma already contains immature or primitive follicles known as primordial follicles.
In the cortex of each ovary of every female child, 100,000 to 200,000 primordial follicles can be found, although not all of them reach maturity.
As the child grows, the primitive structures become mature and are known as Graafian follicles.
With the onset of puberty, one Graffian follicle grows more rapidly each month than the others.
And after its full development, it bursts, releasing a mature ovum. This process is called ovulation.
The empty Graffian follicle starts to undergo certain changes and develops into a corpus luteum (a yellow body).
If fertilisation does not take place, the corpus luteum lasts for two weeks, then fibrosis occurs, and so it turns into corpus albicans (white body) then into the final stage of corpus fibrosum.
If the ovum becomes fertilized, the corpus luteum does not die but increases in size. It produces progesterone and a little amount of oestrogen under the influence of the Luteinizing hormone from the anterior pituitary gland. This maintains pregnancy until the placenta has developed sufficiently to fulfil its own function at 12 weeks of gestation.

Tunica albuginea – This is a dense fibrous coat which surrounds the cortex.

Germinal epithelium encloses the ovary.

Blood Supply: Ovarian arteries.
Venous drainage: Is into the ovarian veins.
Lymphatic drainage: Into the lumbar glands.
Nerve supply: Ovarian plexus.

Supports

The fossa where it lies.
The ovarian ligament.
The broad ligament that extends between the uterine tube and the ovary.
Ovarian fimbria and infundibulo-pelvic ligament.

Ovarian Functions:

Produce ova and female sex hormones—predominantly estrogen and progesterone.
Oestrogen promotes the development of secondary sex characteristics, growth, and maturity of reproductive organs.
Progesterone prepares the endometrium for pregnancy, aids in placental development, breast enlargement during pregnancy, and inhibits ovum production during gestation.
Together, estrogen and progesterone regulate menstrual cycle changes in the endometrium.

Clinical note:

The ovaries may become infected with microorganisms (Oophritis), a fertilized ovum may embed in the ovary (Ovarian pregnancy) and tumors and cysts can affect them as well.

Revision questions

Describe the development of the Graffian follicle.
Describe the cortex of the ovary.
State two functions of the medulla.
State two hormones produced by the ovary.
With the aid of a diagram, describe the mature ovary.
Define ovulation.
Give three reasons why ovulation takes place.
List four ovarian supports.
State two functions of the ovary.

Uterus, Fallopian tubes and Ovaries Read More »

Pelvic Assessment During Labor

A mother who is pregnant for the second time (Gravida 2, Para 1+0) reports with labor pains. Your task is to perform an internal pelvic assessment and create a plan for the mode of delivery.

Pelvic Assessment

Pelvic assessment is a process to determine whether a mother’s pelvis is wide enough for a baby to pass through safely during delivery.

Methods of Pelvic Assessment

External Pelvic Assessment: This is a non-invasive assessment that can be performed by a midwife or healthcare provider. It involves observing the woman’s physical characteristics and taking a detailed history.
Internal Pelvic Assessment: This is a more invasive assessment that requires a vaginal examination. It is typically performed by a doctor, especially during labor.

External Pelvic Assessment

The woman is observed/as she moves towards the HCW/ midwife, note the stature, gait and shape of the abdomen. Any mother with a pendulous abdomen is suspected of having a contracted pelvis.

1. Observation:
Observe the woman as she approaches. Pay attention to her;

Stature: Observe the woman’s height and build. A woman with a shorter stature might have a smaller pelvis.
Gait: Observe how the woman walks. A waddling gait can indicate a wider pelvis.
Abdomen: Observe the shape of the abdomen. A pendulous abdomen (protruding belly) can suggest a contracted pelvis

2. History Taking:

Social History:
- - Age:
Under 18 years may indicate an immature pelvis with smaller diameters.
Over 30 years may suggest that the pelvic joints are less flexible due to ossification, making labor more difficult.
- - Tribe: Some tribes are known to have smaller or larger pelvises, which can influence delivery outcomes.
Medical History:
Ask if the mother has had diseases like poliomyelitis or rickets, which can affect the pelvis’s shape and size.
Surgical History:
Inquire about any accidents or surgeries involving the spine, pelvis, or lower limbs, as these may lead to a contracted pelvis.
Past Obstetrical History:

This is especially important for mothers who have been pregnant before (multigravida).
Ask about previous deliveries: Were they normal or assisted?
Ask about the condition of babies at birth: This can help rule out obstructed labor.
Ask about the baby’s health: This can help rule out mental retardation, which could be a result of abnormal labor.
Ask about the baby’s birth weight: This gives an idea of the size of baby that can pass through the pelvis without complications.

3. General Examination:

Shoe Size: A woman wearing a smaller shoe size (size 4 or less) might have a smaller pelvis.
Size of Hands and Feet: Smaller hands and feet can indicate a smaller pelvis.
Height: A woman shorter than 152 cm might have a smaller pelvis that may not allow an average-sized baby to pass through.

Internal Pelvic Assessment

Internal pelvic assessment is usually done around 36 weeks of pregnancy for first-time mothers (primigravida) or by a midwife during labor. This assessment helps determine if the pelvis can accommodate the baby during delivery.

Scenario

A mother who is pregnant for the third time (Gravida 3, Para 1) arrives with labor pains. Your task is to perform a pelvic assessment to evaluate pelvic capacity.

Objectives

Prepare the necessary equipment for an internal pelvic assessment.
Conduct the internal pelvic assessment for the mother in labor.

Requirements

A pack containing

Two receivers
A gallipot of sterile swabs
Clean pad, Antiseptic lotion, Sterile gloves, Sterile bowl for lotion, Clean gloves, Lubricant, Mackintosh and draw sheet.

At the bedside

Screen
Hand washing equipment
Bedpan

NOTE: Measure the length of your fingers from the curve of the thumb to the middle finger, to measure the diagonal conjugate.

Procedure

Step	Action	Rationale
1	Explain the procedure to the mother using soft skills.	To ensure the mother understands and feels comfortable.
2	Ask the mother to empty her bladder and provide privacy by screening the bed.	To allow accurate assessment and maintain the mother’s privacy.
3	Put on clean gloves.	To maintain hygiene.
4	Assist the mother into the dorsal position.	To allow proper access for the examination.
5	Place the mackintosh and draw sheet under her buttocks.	To provide a clean field.
6	Drape the mother.	To create a sterile area for the procedure.
7	Remove gloves, wash hands, and put on sterile gloves.	To prevent infection.
8	Observe the vulva.	To rule out any abnormalities.
9	Swab the vulva.	To prevent infection.
10	Lubricate the index and middle fingers of your dominant hand and insert them into the vagina, reaching under the symphysis pubis to feel for the sacral promontory. This must not be prominent /tipped as this will reduce the Anteroposterior diameter of the pelvic brim.	To measure the diagonal conjugate.
11	Examine the sacral hollow, ensuring it is well curved, to allow proper rotation off the fetal head.	To check if internal rotation of the fetal head is possible.
12	Feel the left and right greater sciatic notches. They should be wide and round.	To assess the transverse diameter of the pelvic outlet.
13	Feel for the ischial spines; they should be blunt and round, not sharp, not to reduce the diameters of the outlet. If prominent, it can cause obstructed labour.	Prominent spines can obstruct labor.
14	Examine the subpubic arch; it should accommodate two fingers with some space left.	If the space is less, it may reduce the pelvic outlet diameter.
15	Place four knuckles between the ischial tuberosities.	To measure the intertuberous diameter.
16	Clean the vulva, make the mother comfortable, and provide feedback.	To ensure the mother knows her status.
17	Clear the surroundings and record findings.	For follow-up and documentation.

Note:
During labour, while performing pelvic assessment, also assess the station of the fetus. Stations indicate how far the fetus has descended into the pelvis and can be felt during a vaginal examination, especially at stations -3, -2, and -1.

Station Table:

Station	Measurement from the Ischial Spine	Part of the True Pelvis
-3	-5 cm	Pelvic inlet or brim
-2	-3.3 cm
-1	-1.6 cm
0	0	Ischial spine
+1	+1.6 cm	Pelvic outlet
+2	+3.3 cm
+3	+5 cm

The table represents fetal station measurements during labor, which describe the position of the fetus’s presenting part (usually the head) in relation to the maternal ischial spines.
The ischial spines are bony protrusions in the pelvis and serve as a key landmark in determining the station.

Stations and their Significance:

Station 0: When the fetal head is at the level of the ischial spines, it is said to be at “0 station.” This is considered the midpoint, meaning the fetal head has engaged in the pelvis but hasn’t descended past the spines.

Negative Stations (-3 to -1): When the fetal head is above the ischial spines, it is in a negative station. The numbers reflect the distance in centimetres above the spines. For example:

-3 Station: The head is 5 cm above the ischial spines, closer to the pelvic inlet.
-2 Station: The head is 3.3 cm above the ischial spines, indicating descent but not yet engaged.

Positive Stations (+1 to +3): When the fetal head is below the ischial spines, it is in a positive station. The numbers reflect the distance in centimetres below the spines:

+1 Station: The head is 1.6 cm below the ischial spines.
+3 Station: The head is 5 cm below the ischial spines, nearing the pelvic outlet, indicating significant descent and progress toward delivery.

PELVIC ASSESSMENT CHECKLIST

PELVIC ASSESSMENT Read More »

Introduction To Obstetric Anatomy

This field focuses on the anatomical structures involved in pregnancy, labor, and the postpartum period. Key areas of study include the pelvis, pelvic floor, female reproductive system, female breast, male reproductive system, embryology, fetal skull, and the female urinary system.

Definition of Terms

Anatomy: The study of the structures of the body.
Physiology: The study of how the body functions.
Obstetrics: A branch of medicine that focuses on pregnancy, childbirth, and the postpartum period (puerperium).

The Female Pelvis

The pelvis, or pelvic girdle, is a bony structure that forms a canal through which a fetus passes during birth.

Location: The pelvis is positioned between the movable vertebral column, which it supports, and the lower limbs, upon which it rests. It connects to the fifth lumbar vertebra above and the head of the femur (thigh bone) in the acetabulum (hip socket) below.

Shape: The pelvis resembles a bony basin.

Size: It is the largest bony structure in the body, with size varying based on individual age and body size.

Structure: The pelvis consists of the following components:

Bones
Joints
Ligaments

Bones of the Pelvis

1. The Innominate Bones:

These are two large bones on either side of the sacrum, where the femur bones connect. Each innominate bone is made up of three parts that meet at a cup-shaped depression known as the acetabulum:

Ilium:
The largest and flared-out part of the innominate bone. It articulates with the alae (wings) of the sacrum and forms the upper two-fifths of the acetabulum.

Iliac Crest: The upper border of the ilium.
Anterior Superior Iliac Spine: The point where the iliac crest ends at the front.
Anterior Inferior Iliac Spine: Located about 2.5 cm below the anterior superior iliac spine.
Posterior Superior Iliac Spine: The point where the iliac crest ends at the back.
Posterior Inferior Iliac Spine: Located about 2.5 cm below the posterior superior iliac spine. This marks the upper border of the greater sciatic notch, where the sciatic nerves pass.

Ischium:
The lowest part of the innominate bone, forming the lower two-fifths of the acetabulum.

Ischial Tuberosity: The body of the ischium, where the body rests.
Ischial Spine: Located about 2.5 cm above the ischial tuberosity. It divides the lesser and greater sciatic notches.

Pubis:
The smallest part, forming the lowest fifth of the acetabulum. It includes the superior ramus, body, and inferior ramus. The two pubic bones join at the symphysis pubis.

Superior Ramus: The upper part of the pubis.
Body: The main part of the pubis.
Inferior Ramus: The lower part of the pubis.
Symphysis Pubis: The right and left pubic bones fuse together with a pad of cartilage at the symphysis pubis.
Obturator Foramen: The space surrounded by the inferior and superior pubic rami.

2. The Sacrum:

A wedge-shaped structure made up of five fused sacral vertebrae, with foramina (holes) through which blood vessels, nerves, and lymphatics pass. The sacrum is smooth inside to protect organs and rough outside for muscle attachment.
Parts of the Sacrum:

Sacral Promontory: The upper border of the first sacral vertebra, projecting forward over the hollow of the sacrum.
Hollow of Sacrum: The smooth, concave anterior surface.
Alae of Sacrum: Wing-like extensions on each side of the first sacral vertebra.
Sacral Canal: Runs through the center of the bone and opens at the level of the fifth sacral vertebra. It provides a passage for the spinal cord and spinal nerves. At the level of the second and third sacral vertebrae, the nerves spread out to form the Cauda equina (horse’s tail).

3. The Coccyx:

A vestigial tailbone, made up of four fused coccygeal vertebrae. It is triangular in shape and articulates with the sacrum at the sacro-coccygeal joint.

Pelvic Joints

1. Sacroiliac Joints:
The strongest joints in the body, located between the first two sacral vertebrae and the ilium. These joints allow limited movement and are supported by ligaments.

Location: Between the first two bodies of the sacral vertebrae and the upper surface of the ilium.
Function: Strongest joints in the body, allowing limited movement. They are surrounded and supported by ligaments.

2. Symphysis Pubis:
A pad of cartilage between the two pubic bones, forming a cartilaginous joint that unites the pubic rami.

Definition: A pad of cartilage lying between the two bodies of the pubic bone.
Function: A cartilaginous joint uniting the two rami of the pubic bone.
Size: Approximately 4 cm in length, with supporting ligaments around it. Clinical Note:
During pregnancy, the hormone progesterone relaxes and softens the smooth muscles of these joints, causing backache and pain at the symphysis.

3. Sacrococcygeal Joint:
This joint allows the coccyx to bend backward during labor, providing more room for the fetal head to pass through the birth canal.

Location: Where the base of the coccyx articulates with the tip of the sacrum.
Function: Allows a bend backwards during labor, providing more room for the fetal head as it passes through the birth canal.

Pelvic Ligaments

These strong fibrous bands strengthen the pelvic joints and support the pelvic organs. They include:

Sacro-Iliac Ligaments: Strengthen the sacroiliac joint.
Sacro-Tuberous Ligaments: Stretch from the lower sacrum to the ischial tuberosities.
Sacro-Spinous Ligaments: Extend from the lower sacrum to the ischial spines, forming the posterior wall of the pelvic outlet.
Inter-Pubic Ligament: Strengthens the pubic bones.
Inguinal Ligaments: Extend between the anterior superior iliac spine and the pubic body.
Lacuna Ligaments: Lie beneath the inguinal ligaments.
Sacro-Coccygeal Ligament: Strengthens the sacro-coccygeal joint.
Obturator Ligaments: Cover the obturator foramen, allowing the passage of blood vessels, nerves, and lymphatics.

Divisions of the Pelvis

The pelvis is divided into:

1. The Lesser or True Pelvis (Pelvis Minor): The lower part of the pelvis, crucial in childbirth.

Location: The bottom part of the false pelvis.
Importance: It is for childbirth as it forms the birth canal.
Components:

Brim (Inlet): The ring-shaped bone separating the false pelvis from the true pelvis.
Cavity: The space between the brim and the outlet.
Outlet: The lowest part of the true pelvis.

2. The Greater or False Pelvis (Pelvis Major): The upper part, less important in midwifery.

Location: The part above the pelvic brim.
Importance: Less significant in midwifery.

The True Pelvis

Brim/Inlet: A ring-shaped bone separating the false pelvis from the true pelvis.

Importance: The site where the engagement of the fetal head takes place.
Shape: Round, except where the sacral promontory projects into it.
Circumference: Approximately 36 cm, allowing a fetal head with a circumference of 35 cm to pass.

Landmarks:

Promontory of the sacrum
Alae of the sacrum
Sacroiliac joint
Ilio-pectineal eminence
Superior pubic ramus
Upper inner border of the body of the pubic bone
Upper border of the symphysis pubis
Ilio-pectineal line

Important Landmarks:

Sacral Promontory: If prominent, it can reduce the antero-posterior diameter, obstructing labor.
Ilio-pectineal Eminence: Important for determining the fetal head’s position. Important because it’s the point where the denominator (the presenting part of the fetus) faces during labor.
Symphysis Pubis: If narrow, it reduces the antero-posterior diameter.
Engagement: The oblique diameter is crucial for the engagement of the fetal head.

Diameters of the Pelvic Brim/Inlet:(11-12-13)

Antero-Posterior Diameter: Measures 11 cm from the sacral promontory to the upper inner border of the symphysis pubis. Three conjugates are involved: anatomical (12 cm), obstetrical, and diagonal (12-13 cm, subtracting 1-2 cm for tissues).
Oblique Diameters: Right and left, measuring 12 cm from the sacro-iliac joint to the ilio-pectineal eminence.
Transverse Diameter: The largest diameter on the brim, measuring 13 cm from the ilio-pectineal line.

The Pelvic Outlet

Definition: The lowest part of the true pelvis.
Significance: Forms the narrow pelvic strait through which the fetus must pass.
The pelvic outlet is the narrowest part of the pelvis, through which the fetus must pass.
Shape: Diamond-shaped.
Circumference: 36 cm.

Measurements of the outlet:

Antero-posterior Diameter: Measured from the lower border of the symphysis pubis to the lower border of the sacrum (13 cm).
Oblique Diameter: Difficult to measure accurately due to the stretching of the sacro-tuberous ligaments by the fetal head. It’s accepted to lie parallel to the oblique diameter of the brim and cavity and should be at least 12 cm.
Transverse Diameter: Measured between the ischial spines (11 cm).

Important Landmarks of the Pelvic Outlet:

Coccyx: Important because it tilts (extends) backwards during labor to give more room for the passing fetus.
Sub-pubic Arch: Should accommodate at least two fingers and leave space for the passage of the baby.
Ischial Spines: Should be round. If prominent, they reduce the transverse diameter and obstruct labor.
Sacro-spinous Ligament: Should be soft and stretch outwards for the baby to pass.

Functions of the Pelvis:

Birth Canal: Provides the passage through which the fetus must pass to be born.
Protection: Contains and protects internal reproductive organs such as the bladder, uterus, and vagina.
Weight Transmission: Transmits the weight of the trunk to the legs, acting as a bridge between the femurs.
Movement: The primary function of the pelvic girdle is to allow movement of the body.
Sitting and Kneeling: Permits a person to sit or kneel.
Nerve Transmission: The sacrum transmits the cauda equina (the continuation of the nerve roots in the lumbar and sacral region) to and conveys nerves to various parts of the pelvis.

Types of Pelvis

There are four main types of pelvis, each with distinct characteristics:

Gynaecoid Pelvis (Normal Female Pelvis)

The normal female pelvis for childbirth. Found in women of average weight and height with a shoe size 4 or larger.

Characteristics:

Brim: Round, except where the sacral promontory protrudes slightly inward.
Cavity: Generous fore pelvis (the part in front of the transverse diameter), shallow cavity, broad, and well-curved sacrum.
Outlet: Blunt ischial spines, well-rounded sciatic notches, and a subpubic angle of 90 degrees.

Effects on Labour:

The rounded shape is favourable for childbirth. The fetus presents with its head in the occipito anterior position, which aligns with the rounded part of the pelvis, facilitating a smoother labor.
Favorable for the fetus at the start of labor because the pelvis is well-rounded anteriorly, allowing the fetus to present with the most rounded part of its head (occipital anterior).

Android Pelvis (Male-like Pelvis)

Resembles a male pelvis. Found in short and heavily built women.

Characteristics

Brim: Heart or triangular-shaped.
Cavity: Narrow fore pelvis, deep cavity, and straight sacrum.
Outlet: Prominent ischial spines, narrow sciatic notches, and a subpubic angle less than 90 degrees.

Effects on Labour:

Brim: Favours a posterior position of the occiput (fetus presents with the occiput lying posteriorly).
Outlet: May become obstructed at the outlet due to prominent ischial spines reducing the transverse diameter (Deep transverse arrest). Emergency Caesarean section is often necessary.

Platypelloid Pelvis (Flat Pelvis)

A flat pelvis characterized by a kidney/bean-shaped brim and a short anteroposterior diameter.

Characteristics

Brim: Kidney or bean-shaped with a short anteroposterior diameter.
Cavity: Wide transverse diameter, flat sacrum, and shallow cavity.
Outlet: Blunt ischial spines, wide sciatic notches, and a subpubic angle greater than 90 degrees.

Effects on Labour:

The fetus’s head usually engages in the transverse diameter. However, due to the narrow anteroposterior diameter, the head may require tilting (asynclitism) to pass through, sometimes leading to face presentation or requiring a Caesarean section if the head remains high.

Engagement: The head must engage with the sagittal suture in the transverse diameter.
Descent: Descent through the cavity is usually without difficulty.
Asynclitism: Lateral tilting of the head is necessary to allow the bi-parietal diameter to pass the narrowest anteroposterior diameter of the brim.
Presentation: Can result in face presentation.
Contracted Brim: If the brim is severely contracted, the fetal head remains floating high above it, requiring a Cesarean section.

Anthropoid Pelvis

Found in tall women with narrow shoulders.

Characteristics

Brim: Long oval shape, with a longer anteroposterior diameter than the transverse diameter.
Cavity: Long, deep sacrum with side walls that diverge.
Outlet: Less prominent ischial spines, very wide sciatic notch, and a subpubic angle greater than 90 degrees.

Effects on Labour:
Labour is usually not problematic, but the fetus often remains in a posterior position, leading to delivery with the face towards the pubis instead of the perineum.

Labor: Usually does not present any difficulties.
Position: Direct occipito posterior position is often a feature, and the position adopted for engagement may persist up to delivery.
Delivery: The fetus passes through the pelvis remaining in the same position and so delivers face to pubis instead of face to perineum.

Summary of Pelvic Types

Features	Gynaecoid	Android	Anthropoid	Platypelloid
Brim	Rounded	Heart-shaped	Long oval	Kidney-shaped
Fore pelvis	Generous	Narrow	Narrowed	Wide
Side walls	Straight	Convergent	Divergent	Divergent
Ischial spines	Blunt	Prominent	Blunt	Blunt
Sciatic notch	Rounded	Narrow	Wide	Wide
Subpubic angle	90°	<90°	>90°	>90°
Incidence	50%	20%	25%	5%

Other Pelvic Variations

These variations can result from developmental anomalies, dietary deficiencies, injuries, or diseases. They often lead to a contracted pelvis, where one or more diameters are reduced, complicating the normal labor process.

1. Developmental Anomalies.

Robert’s Pelvis: The sacrum’s wings are underdeveloped or absent, causing contraction in all diameters, requiring a Caesarean section.
Naegele’s Pelvis: The sacrum has only one wing due to congenital abnormalities or disease, a true Naegele’s pelvis may occur in a woman who has walked with a limp for many years, also requiring a Caesarean section.
Assimilation Pelvis: Can be high (six vertebrae in the sacrum) or low (four vertebrae in the sacrum). Normal is 5.

High Assimilation Pelvis: The sacrum consists of six vertebrae.
Low Assimilation Pelvis: The sacrum consists of four vertebrae.

Justominor Pelvis: A smaller version of the gynaecoid pelvis, common in petite women, with proportional reductions in all measurements. A Gynaecoid type of pelvis where all measurements are reduced but in correct proportions. Common in petite women of small stature. Effects on Labor:

Small Baby: Can be delivered vaginally with little or no problems.
Large Baby: May require Cesarean section.

2. Dietary Deficiencies.

Rachitic Pelvis: Deformity due to rickets, which affects the person in early childhood due to lack of vitamin D and calcium.
Osteomalacic Pelvis: An extreme deformity due to osteomalacia from dietary deficiencies, caused by a deficient diet and lack of vitamin D, leading to softening of the bones and a Y-shaped pelvic brim.

3. Injuries and Diseases.

Asymmetrical Pelvis: May result from congenital hip dislocation or polio, causing distortion on one side.

Main Differences Between Male and Female Pelvis

Feature	Male	Female
General structure	Thick and heavy	Thin and light
Muscle attachments	Well marked	Poorly marked
False pelvis	Deep	Shallow
True pelvis	Narrow and deep	Wide and shallow
Superior pelvic aperture	Heart-shaped	Oval or rounded
Inferior pelvic aperture	Comparatively small	Comparatively large
Subpubic angle	Narrow	Wide
Obturator foramen	Round	Oval
Acetabulum	Large	Small

Revision Questions

Describe the four bones of the gynaecoid pelvis.
Describe the innominate bones.
List four diameters of the pelvic brim.
Outline three important landmarks of the pelvic brim.
Describe the three parts of the true pelvis in structure.
List four joints of the pelvis.
Outline six ligaments of the pelvis.
Describe the main four types of pelvis.
A prime gravida at 36 weeks of gestation comes for antenatal care. How would you assess her pelvis?
Explain five causes of a contracted pelvis.

Female Pelvis Read More »

THE NON-PREGNANT UTERUS

Microscopic structure of the uterusThere are three layers of tissue from within.

Relations to the uterus

Supports

Functions of the Uterus:

Clinical note

Guiding questions

Clinical procedure: Antenatal Examination

Fallopian Tubes

Ovaries:

Pelvic Assessment During Labor

Pelvic Assessment

Methods of Pelvic Assessment

External Pelvic Assessment

Internal Pelvic Assessment

Scenario

Procedure

Station Table:

PELVIC ASSESSMENT CHECKLIST

Introduction To Obstetric Anatomy

The Female Pelvis

Bones of the Pelvis

1. The Innominate Bones:

2. The Sacrum:

3. The Coccyx:

Pelvic Joints

Pelvic Ligaments

Divisions of the Pelvis

The True Pelvis

Important Landmarks:

The Pelvic Outlet

Measurements of the outlet:

Important Landmarks of the Pelvic Outlet:

Functions of the Pelvis:

Types of Pelvis

Gynaecoid Pelvis (Normal Female Pelvis)

Android Pelvis (Male-like Pelvis)

Platypelloid Pelvis (Flat Pelvis)

Anthropoid Pelvis

Other Pelvic Variations

Microscopic structure of the uterus
There are three layers of tissue from within.