Uterus

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Abdomen • Anatomy

UTERUS

The uterus is a child-bearing organ in females. It lies in the pelvis between the bladder and rectum.

1

Tubectomy

  • For purposes of family planning, a woman can be sterilized by removing a segment of the uterine tube on both sides.
  • This can be done by:
    • Laparoscopy.
    • Through an incision in the abdominal wall.
2

Uterus — Definition / General Features

  • Uterus is a child-bearing organ in females.
  • It lies in the pelvis between the bladder and rectum.
  • It is a thick-walled, firm, muscular organ.
  • It protects and provides nutrition to a fertilized ovum, enabling it to grow into a fully formed foetus.
  • During childbirth or parturition, contractions of the muscles in its wall result in expulsion of the foetus from the uterus.

Synonyms

  • In layman’s language → womb.
  • Also called hystera.
  • The word hysterectomy is based on hystera.
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Size and Shape

Shape

Pyriform.

Weight

30–40 g

Length

3 inches (7.5 cm)

Breadth

2 inches (5 cm)

Thickness

1 inch (2.6 cm)

Consistency

Firm.

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Subdivisions / Parts of Uterus

The uterus is divided into two regions:

1. Muscular body of uterus

Forms upper 2/3rd part.

2. Fibrous cervix

Forms lower 1/3rd part.

  • Junction of the body and cervix is marked by a circular constriction called the isthmus.
  • The part of the uterus above the opening of the fallopian tube is called the fundus.
  • The superolateral angle of the body at the junction of body and fundus projects outwards and is called the cornua of uterus.

Structures Attached to the Cornua

  • Uterine tube
  • Ligament of ovary
  • Round ligament.

Communications

Superiorly

Uterus communicates on each side with the uterine tube.

Inferiorly

Uterus communicates with the vagina.

5

Normal Position and Angulation

1. Anteversion

  • The angle of anteversion is a forward angle between:
    • Long axis of body of uterus
    • Long axis of vagina.
  • Normally → about 90°, opening forwards.
  • Forward tilting of the uterus relative to the vagina → anteversion.

2. Anteflexion

  • The angle of anteflexion is a forward angle between:
    • Long axis of body of uterus
    • Long axis of cervix at the isthmus.
  • Measures about 120°–170°.
  • The uterus is also slightly flexed at the level of the internal os of cervix → anteflexion.
Note
  • Roughly, the long axis of the uterus corresponds to the axis of the pelvic inlet.
  • Axis of the vagina corresponds to the axis of the pelvic cavity and pelvic outlet.
  • Normally, the uterus is deviated to the right side → dextrorotation.

Retroversion

In a retroverted uterus, the uterus is tilted or tipped backward relative to the vagina.

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Features of Uterus

The uterus comprises:

1. Body

  • Fundus
  • Two surfaces:
    • Anterior or vesical
    • Posterior or intestinal
  • Two lateral borders

2. Cervix

Body of Uterus

Fundus

  • Fundus is formed by the free upper end of the uterus.
  • It lies above the openings of the uterine tubes.
  • It is convex like a dome.
  • It is covered with peritoneum.
  • It is directed forward when the bladder is empty.
  • The fertilized oocyte is usually implanted in the posterior wall of the fundus or upper part of the body of uterus.

Surfaces and Borders

1. Anteroinferior Surface

  • Flat.
  • Related to the urinary bladder.
  • Covered with peritoneum.
  • Forms the posterior or superior wall of the uterovesical pouch.

2. Posterosuperior Surface

  • Convex.
  • Related to:
    • Coils of terminal ileum
    • Sigmoid colon.
  • Covered with peritoneum.
  • Forms the anterior wall of the rectouterine pouch.

3. Lateral Borders

  • Rounded and convex.
  • Provides attachment to the broad ligament of uterus, which connects it to the lateral pelvic wall.
  • Uterine tube opens into the uterus at the upper end of this border.

Attachments at the Upper End of Lateral Border

  • Round ligament of uterus → anteroinferior to the uterine tube.
  • Ligament of ovary → posteroinferior to the uterine tube.
  • Uterine artery ascends along the lateral border of uterus between the two layers of the broad ligament.

Usual Site of Implantation

On the 7th day after fertilisation, the blastocyst usually implants in the endometrium of the uterus at the posterior wall of the superior part of uterus.
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Cervix of Uterus

  • Cervix is the lower, cylindrical part of the uterus.
  • It is less mobile than the body.
  • About 2.5 cm long.
  • Slightly wider in the middle than at either end.
  • The lower part of the cervix projects into the anterior wall of the vagina.
  • It divides into:
    • Supravaginal part
    • Vaginal part.

A. Supravaginal Part

Related to:

  1. Anteriorly → bladder.
  2. Posteriorly → rectouterine pouch containing coils of intestine and rectum.
  3. On each side → ureter and uterine artery, embedded in parametrium.
  • The fibrofatty tissue between the two layers of the broad ligament and below it is called the parametrium.
  • It is most abundant near the cervix and vagina.

B. Vaginal Part

  • Projects into the anterior wall of vagina.
  • Spaces between it and the vaginal wall are called vaginal fornices.
  • Cervical canal opens into the vagina through an opening called the external os.
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Cavity of Uterus

Cavity of Body of Uterus

  1. In sagittal section:
    • Cavity appears as a mere slit because the uterus is compressed anteroposteriorly.
  2. In coronal section:
    • Cavity is triangular in shape.
    • Apex is directed downwards.
  3. At the apex:
    • Cavity becomes continuous with the canal of the cervix.
    • Junction is called the internal os.
  4. Superolateral angles of the cavity:
    • Receive the openings of the right and left uterine tubes.

Cervical Canal

  • Cavity of cervix is fusiform in shape.
  • Communicates:
    • Above → with cavity of body of uterus through internal os.
    • Below → with vaginal cavity through external os.
  • Canal is flattened from before backwards, giving it:
    • Anterior wall
    • Posterior wall.
  • These walls show mucosal folds resembling branches of a tree called arbor vitae uteri.
  • Folds in anterior and posterior walls interlock with each other and close the canal.

External Os

In a nulliparous woman

Woman who has not borne children:

  • External os is small and circular.

In multiparous women

External os is bounded by:

  • Anterior lip
  • Posterior lip.
  • Both lips are in contact with the posterior wall of the vagina.
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Relations of the Uterus

Relations of Body

Anterior

  • Uterovesical pouch.
  • Surface of urinary bladder.

Posterior

  • Rectouterine pouch.
  • Coils of ileum.
  • Sigmoid colon.

Lateral

  • Broad ligament.
  • Ureter.
  • Uterine vessels.

Relations of Cervix

Anterior

Supravaginal part of cervix → related to posterior surface of urinary bladder.

Posterior

  • Supravaginal part of cervix → related to rectouterine pouch with coils of ileum and sigmoid colon.
  • Vaginal part of cervix → related to posterior fornix of vagina.

Laterally

  • Supravaginal part of cervix → related to ureter and uterine vessels.
  • Vaginal part of cervix → related to fornices of vagina.
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Ligaments of Uterus

Peritoneal Ligaments

  • These are mere peritoneal folds.
  • They do not provide any support to the uterus.

1. Anterior ligament

Consists of uterovesical fold of peritoneum.

2. Posterior ligament

Consists of rectovaginal fold forming rectovaginal pouch of peritoneum.

3. Right and left broad ligaments

  • Folds of peritoneum.
  • Attach uterus to the lateral pelvic wall.

4. Rectouterine folds

Right and left.

Fibromuscular Ligaments

  1. Round ligaments of uterus.
  2. Transverse cervical ligaments.
  3. Uterosacral ligaments.

These are described separately under the heading of supports of uterus.

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Broad Ligament of Uterus

Paired folds of peritoneum extending from the lateral borders of uterus to the lateral wall of pelvis on each side.

External Features

Two Surfaces

When bladder is empty

  • Superior
  • Inferior

When bladder is full

  • Anterior
  • Posterior.

Two Borders

When bladder is empty

  • Anterior free border
  • Posterior attached border.

When bladder is full

  • Upper free border
  • Inferior attached border.

Parts of Broad Ligament

1. Mesosalpinx

Part of broad ligament between the uterine tube and ligament of ovary.

2. Mesometrium

Part of broad ligament extending from the pelvic floor to the ovary, ligament of ovary and body of uterus.

3. Mesovarium

Fold of peritoneum extending posteriorly from the broad ligament to the ovary.

4. Infundibulopelvic ligament

  • Also called suspensory ligament of ovary.
  • Part of broad ligament extending from the infundibulum of uterine tube to the upper part of lateral wall of pelvis.

Contents of Broad Ligament

1. One tube

  • Uterine tube.

2. Two ligaments

  • Round ligament of uterus.
  • Ligament of ovary.

3. Arteries

  • Uterine artery.
  • Ovarian artery.

4. Nerve plexuses

  • Uterovaginal plexus.
  • Ovarian plexus.

5. Embryological remnants

  • Epoophoron.
  • Gartner’s duct.
  • Paroophoron.
  • Vesicular appendices.

6. Lymph nodes and lymphatic vessels.

7. Fibrofatty tissue / parametrium.

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Arterial Supply

The uterus is supplied:

1. Chiefly by two uterine arteries

They are markedly enlarged during pregnancy.

2. Partly by ovarian arteries.

Uterine Artery

  • Branch of the anterior division of internal iliac artery.
  • First runs medially towards the cervix.
  • Crosses the ureter:
    • Above the lateral fornix of vagina.
    • 2 cm lateral to cervix.
  • Then ascends along the side of the uterus with a tortuous course.
  • Finally runs laterally towards the hilus of ovary.
  • Ends by anastomosing with the ovarian artery.
  • Tortuosity permits expansion of the uterus during pregnancy without stretching the artery.

Branches / Supply to Other Structures

Apart from uterus, it gives branches to:

  • Vagina.
  • Medial 2/3rd of uterine tube.
  • Ovary.
  • Ureter.
  • Structures present in broad ligament.

Venous Drainage

  • Veins form a plexus along the lateral border of uterus.
  • Plexus drains through:
    • Uterine veins.
    • Ovarian veins.
    • Vaginal veins.
  • These drain into the internal iliac veins.
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Lymphatic Drainage

Lymphatics of uterus begin at three intercommunicating networks:

1. Endometrial

2. Myometrial

3. Subperitoneal.

These plexuses drain into lymphatics on the side of uterus as follows:

1. Upper Lymphatics

  • From fundus and upper part of body.
  • Drain mainly into aortic nodes.
  • Drain only partly to superficial inguinal nodes along the round ligament of uterus.

2. Middle Lymphatics

  • From lower part of body.
  • Drain into external iliac nodes.

3. Lower Lymphatics

  • From cervix.
  • Drain into internal iliac and sacral nodes.
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Nerve Supply

  • Uterus is richly supplied by both:
    • Sympathetic nerves
    • Parasympathetic nerves
  • They reach through:
    • Inferior hypogastric plexuses.
    • Ovarian plexuses.

1. Sympathetic Nerves

  • From T12, L1 segments of spinal cord.
  • Produce uterine contraction and vasoconstriction.

2. Parasympathetic Nerves

  • From S2–S4.
  • Produce uterine inhibition and vasodilatation.
  • These effects are complicated by the pronounced effects of hormones on the genital tract.

3. Pain Sensations

From body of uterus

Pass along sympathetic nerves.

From cervix

Pass along parasympathetic nerves.

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Age and Reproductive Changes

In Foetal Life

  • Cervix is larger than the body.
  • Cervix projects a little above the pelvic brim.

At Puberty

  • Uterus enlarges and descends to the adult position.
  • Arbor vitae uteri also appears.

During Menstruation

  • Uterus is slightly enlarged.
  • Becomes more vascular.
  • Lips of external os are swollen.

During Pregnancy

  • Uterus becomes enormously enlarged.
  • Mainly due to hypertrophy of smooth muscle fibres.
  • Partly due to hyperplasia.
  • As pregnancy advances, uterine wall becomes progressively thinner.
  • After parturition:
    • Uterus gradually involutes.
    • Returns almost to non-pregnant size.

In Old Age

  • Uterus becomes atrophic and smaller in size.
  • Becomes more dense in texture.
  • Internal os is frequently obliterated.
  • Lips of external os disappear.
  • External os itself may be obliterated.
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Supports of the Uterus

Uterus is a mobile organ.

It undergoes extensive changes in size and shape during the reproductive period of life.

It is supported and prevented from sagging down by several factors, chiefly muscular and fibromuscular.

Primary Supports

1. Muscular / Active Supports
  • Pelvic diaphragm
  • Perineal body
  • Distal urethral sphincter mechanism
2. Fibromuscular / Mechanical Supports
  • Uterine axis
  • Pubocervical ligaments
  • Transverse cervical ligaments of Mackenrodt
  • Uterosacral ligaments
  • Round ligaments of uterus

Secondary Supports

Of doubtful value.

Formed by peritoneal ligaments:

  1. Broad ligaments.
  2. Vesicouterine pouch and fold of peritoneum.
  3. Rectovaginal or rectouterine pouch and fold of peritoneum.

Role of Individual Supports

1. Pelvic Diaphragm
  • Supports the pelvic viscera.
  • Resists raised abdominal pressure.
  • Pubococcygeus (part of levator ani) inserts on the perineal body and supports the vagina by forming a sling.
  • Rupture of these fibres during childbirth causes loss of support of vagina and it may prolapse.
2. Levator Ani Muscle
  • Fixes the perineal body.
  • Supports the pelvic viscera.
3. Perineal Body
  • Fibromuscular node in the centre of perineum between vagina and rectum.
  • Gives attachments to:
    • Perineal muscles.
    • Pelvic diaphragm.
  • Maintains the integrity of the pelvic floor.
4. Sphincter Urethrae Fibres
  • Compressor urethrae and sphincter urethrovaginalis fibres are inserted into the vagina.
  • Hence, they support the uterus and vagina.
5. Uterine Axis
  • Anteverted and anteflexed position of uterus prevents the organ from sagging down through the vagina.
  • Increased intra-abdominal pressure further accentuates anteversion of uterus.
  • Prevents prolapse of uterus.
6. Pubocervical Ligaments
  • Connect the cervix to the posterior surface of pubic bone.
  • Pair of fibrous bands derived from endopelvic fascia.
  • Correspond to the puboprostatic ligaments in males.
7. Transverse Cervical Ligaments of Mackenrodt

Also called:

  • Cardinal ligaments.
  • Cervical ligaments.
  • Paracervical ligaments.
  • Retinacula uterine sustentaculum of Bonny.
  • Fibrous bands derived from endopelvic fascia.
  • Fan-shaped bands.
  • Connect the lateral aspect of cervix and upper vaginal wall to the lateral pelvic wall.
  • Form a hammock which supports the uterus and prevents its prolapse.
8. Uterosacral Ligaments
  • Pair of fibrous bands derived from condensation of endopelvic fascia.
  • Connect cervix to the second and third sacral vertebrae.
9. Round Ligaments of Uterus
  • Pair of fibromuscular bands.
  • Extend from the lateral angle of uterus.
  • Run forward and laterally.
  • Pass through the deep inguinal ring.
  • Traverse the inguinal canal.
  • Merge with connective tissue of labia majora.
  • Round ligament pulls the fundus forward.
  • Helps to maintain anteversion and anteflexion of the uterus.
Note
  • Surgical tightening of Mackenrodt’s ligament is commonly done for repair of prolapsed uterus.
  • Round ligaments pull the cervix forward, whereas uterosacral ligaments pull backward.
  • They help to maintain the anteflexed and anteverted position of the uterus.

Canal of Nuck

  • Canal of Nuck is a patent extension of peritoneum in the inguinal canal, along with the round ligament.
  • It extends externally up to the labia majora.
  • It is homologous to processus vaginalis in males.
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Histology of Uterus

The body and fundus of the uterus have three layers:

1. Endometrium

2. Myometrium

3. Perimetrium

Endometrium

Consists of:

  • Simple columnar epithelial lining.
  • Simple tubular glands.
  • Connective tissue stroma.

Myometrium

Consists of smooth muscle cells showing:

  • Inner longitudinal fibres.
  • Outer longitudinal fibres.
  • Middle spirally arranged fibres.

Perimetrium

Consists of a connective tissue layer covered by mesothelium.

Cyclic Changes in Endometrium

Proliferative Phase

  • Glands are long with narrow lumen.
  • Stroma is thick.
  • Spiral arteries are less coiled.

Secretory Phase

  • Glands are highly coiled.
  • Lumen is wide.
  • Secretions are present.
  • Stroma has coiled spiral arteries.

Menstrual Phase

  • Endometrium becomes ischaemic.
  • It starts being shed.
  • Vessel wall gets necrosed.
  • Blood enters the stroma.
  • Menstrual flow starts.
UTERUS
Anatomy study notes.