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Uterine anatomy

Overview

  • Size: About 8cm x 5cm x 3cm

  • Fundus

    • Part above the entrance of the tubes
    • Possess a serous coat of pelvic peritoneum which continues over the front and back of the body

  • Body

    • Cornu
      • Upper angle, at the junction of the Fundus and Body
      • Receives the Uterine Tubes
    • Enclosed by peritoneum
      • Becomes the Broad Ligament laterally
    • Intestinal surface – faces upwards with coils of intestine lying upon it
    • Vesical surface – faces downwards resting on the Bladder with the peritoneum of the Vesicouterine Pouch intervening

  • Cervix

    • Lower end clasped by the vault of the Vagina
    • Deep sulcus that surrounds the Cervix = Fornix of the Vagina
      • Deepest posteriorly

  • Peritoneum

    • Posterior surface covered by peritoneum that continues from the body onto the upper part of the Fornix forming the anterior wall of the Rectouterine pouch (of Douglas)
      • NB: Thus, cervix has no direct extra-peritoneal relation to the rectum
    • Anterior surface has no peritoneal covering
      • Deep to the Vesicouterine Pouch
      • Attached to the Bladder above the Trigone by dense connective tissue
        • NB: i.e. attached to the Base of the Bladder

  • Ureter is 2cm from the Cervix as it passes first lateral to and then in front of the Fornix

    • NB: Uterus body is rarely in the midline – when deviated to one side, the Cervix becomes deflected to the opposite side – thus, one Ureter may be closer to the Cervix

  • Internal Os – the point where the Canal of the Cervix is continuous with the cavity of the body

  • External Os – lower opening into the Vagina

    • Circular in the nulliparous
    • Transverse slit after childbirth with anterior and posterior lips – anterior lying at a lower level
    • On a level with the Ischial Spines

  • NB: Forms an angle of 90 degrees or more with the vagina

Uterine Tubes

  • Length: 10cm
  • Medial 1cm (intramural part) embedded within Uterine wall
  • Lies in the upper edge of the Broad Ligament
  • Two layers of smooth muscle – inner circular, outer longitudinal
  • Lined by mucous membrane thrown into folds
  • Surface epithelium – mixture of ciliated and non-ciliated columnar cells
    • Cilia most abundant at fimbriated end (which is least muscular)
  • Mesosalpinx – the peritoneal fold embracing the Uterine Tube
  • Isthmus:
    • The part adjacent to the Uterus
    • Straight and narrow
  • Ampulla:
    • Next to Isthmus
    • More than half the length of the tube
  • Infundibulum:
    • Lateral end of the tube
    • Fimbriated end with finger-like processes, the Fimbriae
    • Open end lies behind the Broad Ligament adjacent to the lateral pelvic wall

Blood Supply

Uterine Artery

  • Supplies Uterus
  • Branch of the Internal Iliac Artery (NB: The anterior division)
  • Passes medially across the Pelvic Floor in the base of the Broad Ligament
  • Above the Ureter
  • Reaches the side of the Supravaginal part of the Cervix
  • Gives branch to the Cervix and Vagina
  • Turns upwards between layers of the Broad Ligament
  • Runs in tortuous manner alongside the Uterus as far as the Cornu
  • Gives off branches which penetrate the Uterine walls and anastomose across midline with corresponding branches of the opposite Uterine Artery
  • At junction of Uterus and Uterine Tubes, artery turns laterally
  • Ends with anastomosing with the Tubal branch of the Ovarian Artery

Ovarian Artery

  • Supplies Uterine Tube and Ovary

Veinous Drainage

  • Course below the artery at the lower edge of the Broad Ligament
  • Form a wide plexus across the pelvic floor
  • Communicates with the Vesical and Rectal Plexuses
  • Drains to the Internal Iliac Veins
  • Tubal Veins join the Ovarian Veins

Lymph Drainage

  • From Cervix:
    • External and Internal Iliac Nodes
    • Sacral Nodes along Uterosacral Ligaments
  • Lower part of Uterine Body:
    • External Iliac Nodes
  • Upper part of Uterine Body, Fundus and Uterine Tube:
    • Accompany lymph from Ovaries
    • Drain to Para-aortic Nodes
    • Few pass to External Iliac Nodes
    • Few from region of Uterine Cornua accompany Round Ligaments to reach the Superficial Inguinal Nodes

Nerve Supply

  • Branches from the Inferior Hypogastric Plexus
  • Smooth muscle of Uterus sensitive to hormonal influences
  • Sympathetic supply:
    • Vasoconstrictor
    • Facilitating function in relation to Uterine muscle
    • Division of all Uterine nerves or high transection of the Spinal Cord does not affect Uterine contractility, even in labour
    • Pain from Upper Cervix and Body of Uterus (including labour pains)
      • Involves T10-L1 – referred to corresponding Dermatomes
    • Pre-sacral neurectomy (cutting hypogastric nerves from the Superior Hypogastric Plexus) does not abolish labour pain, but may improve dysmenorrhoea
    • Abolition of Uterine sensation requires division of all nerves or transection of the cord above T10
  • Pain from Cervix:
    • Carried by Pelvic Splanchnic Nerves
    • Pain from Upper Cervix appears to run with Sympathetic nerves
  • Cervix and Body relatively insensitive to cutting and burning
  • Uterine Tube sensitive to touching and cutting

Structure

Myometrium

  • Smooth muscle
  • Bulk of the Uterus
  • Fibres in 3 layers but ill-defined
  • Outer longitudinal and expulsive
  • More deeply placed are circular and act as sphincters round the larger blood vessels, the openings of the Uterine Tubes and the Internal Os

Endometrium

  • Columnar epithelium that dips down into the endometrial stroma to form the endometrial glands
  • At menstruation, the bases of the glands remain to provide the source for the new epithelial covering
  • Mucosa of Cervix does not take part in the cyclical changes and is not shed at menstruation
    • Surface cells are mucus-secreting and there are also mucous glands
  • Just inside the External Os the epithelium changes to the Stratified Squamous epithelium of the Vagina
  • Outer or serous covering of the Uterus is the Peritoneum

Supports

  • Normal position of Uterus: Anteflexion and Anteversion
    • External os thus opens through the anterior wall of the Vagina
  • 20% of nulliparous females may have a retroverted Uterus
  • Most fixed part of Uterus is Cervix
  • Pubovaginalis part of Levator Ani and the Perineal Body support the Vagina
    • Assists indirectly in holding the Cervix up
    • If muscles unduly stretched or damaged during childbirth, posterior Vaginal wall sinks downwards (prolapses) and this often followed by prolapse or retroversion of the Uterus
    • NB: Thus, it can be said the uterus is supported by the Levator Ani muscle

Broad Ligament

  • Lax double fold of Peritoneum
  • Lies lateral to the Uterus
  • Plays little part in uterine support
  • Medial edge attached to side wall of Uterus
  • Flows over its intestinal and vesical surfaces as its serous coat
  • Lateral edge attached to side wall of pelvis
    • Line of lateral attachment crosses:
      • Obturator Nerve
      • Superior Vesical or Obliterated Umbilical Vessels
      • Obturator Artery and Vein
  • Upper border
    • Free
    • Forms Mesosalpinx
    • Contains Uterine Tube
    • Upper lateral part contains Ovarian Vessels and Lymphatics
    • Extended over the External Iliac Vessels as a fold – Suspensory Ligament of the Ovary
  • Two layers of inferior edge pass forwards and backwards to line pelvic cavity
    • Ureter adhering underneath
  • Anterior layer of Broad Ligament bulged forwards by Round Ligament of Uterus just below the Uterine Tube
  • Posterior layer has a fold projecting backwards suspending the ovary – Mesovarium
  • Between layers of Broad Ligament is a mass of areolar tissue – Parametrium
    • Lies the Uterine Vessels
    • Lymphatics
    • Round Ligament of Uterus
    • Ligament of the Ovary
    • Vestigial remnants of Mesonephric Tubules

Round Ligament of Uterus

  • Comprised of smooth muscle and fibrous tissue
  • Holds the Uterus forwards in anteflexion and anteversion – esp. when forces tend to push the Uterus backwards, e.g. bladder distension, gravity during recumbency Course:
    • Extends from junction of Uterus and Tube to Deep Inguinal Ring
    • Lies in Broad Ligament below Uterine Tube
    • Bulges anterior layer of the Broad Ligament forwards
    • Round Ligament passes through Inguinal Canal
    • Attached at distal extremity to fibrofatty tissue of the Labium Majus of the Vulva
  • Continuous with Ligament of the Ovary (through its uterine attachment)
    • Two ligaments together represent the Gubernaculum
  • Arterial Supply:
    • Branch of Ovarian Artery in the Broad Ligament
    • Branch of Inferior Epigastric Artery in the Inguinal Canal

Transverse Cervical Ligament

  • A.k.a. Lateral Cervical, Cardinal or Mackenrodt’s Ligament
  • Thickenings of connective tissue in the base of each Broad Ligament
  • Extends from Cervix and Vaginal Fornix laterally to the side wall of the Pelvis
  • Following traverse the connective tissue of this ligament:
    • Ureter
    • Uterine Artery
    • Inferior Hypogastric Plexus
  • Imparts lateral stability to the Cervix and an important support of the Uterus
  • Uterosacral Ligaments:
    • Fibrous tissue and smooth muscle
    • Extend backwards from the Cervix below the peritoneum
    • Embraces the Rectouterine Pouch and Rectum
    • Becomes attached to the front of the Sacrum
    • Palpable on rectal exam
    • Keep Cervix braced backwards against forward pull of the Round Ligaments on the Fundus
    • Maintains the body of Uterus in anteversion

Development

  • Paramesonephric (Mullerian) Ducts develop as a linear invagination of the Coelomic Epithelium on the lateral aspect of the Mesonephros
  • Grow caudally lateral to the Mesonephric Ducts
  • Cross ventral to them and fuse at their caudal ends to make the Uterus
  • Continue to reach the dorsal wall of the Urogenital Sinus – forms the upper part of the Vagina
  • Cranial ends persist as the Uterine Tubes
  • Incomplete fusion results in a Median Septum in the Uterus or a Bicornuate Uterus

Surgical Approach

  • Total Hysterectomy:
    • Broad, Round and Ovarian Ligaments and Uterine Tubes divided on each side near the Uterus
    • Lower ends of Ureters need to be safeguarded esp. when Uterine Arteries are divided
    • Anterior and Posterior Vaginal walls cut across below the Cervix
  • If Subtotal Hysterectomy via abdominal route:
    • Cervix is cut across the level of the Lateral Ligaments without opening into the Vagina

Graph View

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