Q4 LONG ANSWER 10M ★ High-yield

Describe the uterus under position, supports, relations and blood supply. Add a note on its applied anatomy.

Anatomy · 1st Professional — Pre-Clinical

General Features

The uterus is a hollow, thick-walled, pear-shaped muscular organ lying in the pelvis between the bladder in front and the rectum behind.

Measures about 7.5 5 2.5 cm and weighs 30–40 g in the nulliparous adult
Parts — fundus (above the entry of the tubes), body, isthmus (the lower 1 cm, which becomes the lower uterine segment in pregnancy), and cervix
Wall — perimetrium, myometrium and endometrium

Normal Position

Anteverted — the long axis of the uterus is bent forward on the axis of the vagina at about 90°
Anteflexed — the body is bent forward on the cervix at about 125°
In about 20% of women the uterus is retroverted, usually a normal variant
The anteverted position is important — rises in intra-abdominal pressure push the uterus against the bladder and the pelvic floor rather than down the vaginal axis, resisting prolapse

Supports of the Uterus

Group	Structures	Importance
Primary — muscular	Levator ani (pelvic diaphragm), perineal body, urogenital diaphragm	The most important supports
Primary — ligamentous (fibromuscular)	Transverse cervical (cardinal, Mackenrodt) ligament; uterosacral ligament; pubocervical ligament	Hold the cervix in position — the true ligamentous supports
Secondary	Round ligament, broad ligament, uterovesical and rectovaginal folds	Of little support value; the round ligament merely maintains anteversion

Relations

Direction	Relation
Anterior	Uterovesical pouch and the urinary bladder
Posterior	Rectouterine pouch (of douglas) with coils of ileum and sigmoid colon; rectum
Lateral	Broad ligament, uterine artery, and the ureter
Superior	Coils of intestine

Blood Supply

Uterine artery — from the anterior division of the internal iliac artery; runs medially in the base of the broad ligament
It crosses above the ureter about 2 cm lateral to the cervix, at the level of the internal os
Mnemonic — "water (ureter) under the bridge (uterine artery)"
It anastomoses with the ovarian artery (from the aorta) in the broad ligament
Veins form the uterine plexus, draining into the internal iliac vein

Region	Lymphatic drainage
Fundus and upper body	Para-aortic nodes (along the ovarian vessels)
Cornu (near the round ligament)	Superficial inguinal nodes — the round ligament traverses the inguinal canal
Body	External iliac nodes
Cervix	Internal and external iliac, obturator and sacral nodes

The Cervix and the Vagina

Feature	Detail
Cervix — parts	Supravaginal and vaginal portions; the external os is round in the nullipara and transverse after childbirth
Cervical canal	Between the internal and external os; lined by columnar epithelium
Squamocolumnar junction	Where columnar meets squamous epithelium; the transformation zone — the site of cervical carcinoma and the area sampled by a Pap smear
Vaginal fornices	Anterior, posterior and two lateral; the posterior fornix is the deepest and is related to the pouch of Douglas
Vagina — relations	Bladder and urethra in front; rectum and anal canal behind, separated below by the perineal body

The posterior fornix gives peritoneal access — the basis of culdocentesis and of posterior colpotomy
Vaginal pH is acid (about 4.5) from the action of Doderlein bacilli on glycogen; this protects against infection and is oestrogen dependent

Applied Aspects

The ureter is at risk in hysterectomy exactly where the uterine artery crosses it; the artery must be ligated close to the uterus, and the ureter identified first. Ureteric injury is the most feared complication of the operation
Uterine prolapse follows weakening of the pelvic floor and the cardinal and uterosacral ligaments, usually after childbirth; graded by the descent of the cervix
Culdocentesis — the pouch of Douglas is the lowest part of the peritoneal cavity in the erect position, and can be aspirated through the posterior fornix to detect blood in a ruptured ectopic pregnancy
Carcinoma of the cervix is the commonest genital malignancy in Indian women; it spreads laterally in the parametrium toward the ureters, causing obstructive uropathy and renal failure, the usual mode of death
Dilatation and curettage must respect the anteverted, anteflexed axis, or the uterus is perforated — the risk is greatest in a retroverted uterus that has not been recognised
The lower uterine segment develops from the isthmus and is the site of the incision in caesarean section, being thinner, less vascular and better healing
Fibroids (leiomyomas) are the commonest uterine tumour; submucous ones cause menorrhagia, subserous ones pressure symptoms
Asherman syndrome — intrauterine adhesions after over-vigorous curettage, causing amenorrhoea and infertility
The endometrium has two layers — the functional layer, shed at menstruation, and the basal layer, which regenerates it; loss of the basal layer is irreversible
Retroverted gravid uterus may become incarcerated in the pelvis and cause acute urinary retention in early pregnancy
Cervical cerclage for cervical incompetence is placed at the level of the internal os, and relies on the anatomy of the isthmus
Adenomyosis — endometrium within the myometrium, causing a bulky tender uterus with dysmenorrhoea, and often confused with fibroids
Uterine anomalies such as bicornuate and septate uterus arise from failure of fusion or of resorption of the paramesonephric ducts, and cause recurrent miscarriage

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