Uterus

Other Names: Hystera, Womb
Uterus is a female reproductive organ present in the pelvis. It serves as a site for the reception, retention, and nutrition of the fertilized ovum. At the time of child birth, contraction of muscles of the uterus results in expulsion of the fetus from the uterus.The uterus is a hollow, pear-shaped organ with thick muscular walls. In nulliparous (women who has not borne child) women uterus is about 40grams, 8cm long, 5cm wide, and 2.5cm thick.

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Description
The uterus is divided into three parts:

  1. Fundus lies superior to the entrance of the uterine tubes.
  2. Body lies inferior to the entrance of the uterine tubes, narrows inferiorly to become continuous with the cervix.
  3. Cervix is the lower cylindrical part of the uterus. It is about 2.5cm in length and slightly wider in the middle than at the ends. The junction between the body and the cervix is marked by a circular constriction. The cervix pierces the anterior wall of the vagina and is subdivided into:
    • supravaginal part
    • vaginal part

Uterine cavity is cavity of the body of the uterus. It is triangular in shape in coronal section, merely a cleft in sagittal section.

Cervical canal is a cavity of the cervix. The canal opens to the uterine cavity through an opening called the internal os and to the vagina through the external os. External os is circular in the nulliparous women and opened out transversely in the multiparous women, so that it presents with an anterior lip and a posterior lip.

Structural layers of the Uterus from inside to outside

  1. Endometrium is an inner lining of the body of the uterus; continuous with the lining of the uterine tubes and the cervix.
  2. Myometrium is a thick muscle layer. It is made up of smooth muscle and connective tissue
  3. Parametrium is an outermost covering of the uterus. It is derived from the pelvic fascia

Anatomical Relations

  • Anterior:urinary bladder, uterovesical (vesicouterine) pouch, and anterior fornix of the vagina
  • Posterior:rectouterine pouch (of Douglas) with coils of ileum or sigmoid colon within it
  • Lateral:broad ligament, uterine artery and vein, ureter, lateral fornices of the vagina, uterine tubes, round ligament of the ovary, round ligament of the uterus

Positions of the Uterus

Normally, in majority of women, the uterus is anteverted and anteflexed
Anteversion: the long axis of body of uterus is bent forward on the long axis of the vagina, forming an angle of 90o
Anteflexion: the long axis of body of uterus is bent forward at the level of the internal os on the long axis of the cervix, forming an angle of 170o

Retroverted: in some women, fundus and body of uterus bent backward on the vagina
Retroflexed: if body of uterus bent backward on cervix

Supports of the Uterus:

I. Primary Supports/ Major Support

  • Muscular/ Active Support:
    1. Pelvic diaphragm
    2. Perineal body
    3. Urogenital diaphragm
  • Fibromuscular & Mechanical Support
    1. Uterine axis
    2. Round ligaments of the uterus: it represent the lower end of the gubernaculum
      extend from the superolateral angle of the uterus, through the inguinal canal, to the labia majora
      helps to keep the uterus anteverted and anteflexed
    3. Condensations of pelvic fascia which form 3 important ligaments
      • Transverse cervical (cardinal; Mackenrodt’s) ligaments – from cervix and upper part of vagina to lateral pelvic wall
      • Pubocervical ligaments – from cervix to symphysis pubis
      • Sacrocervical (uterosacral) ligaments – from cervix and upper end of vagina to lower end of sacrum

II. Secondary Supports/ minor supports

  1. Uterovesical fold of peritoneum
  2. Rectovaginal fold of peritoneum
  3. Broad ligaments: It is a two layered folds of peritoneum that extends across the pelvic cavity from the lateral margins of the uterus to the lateral pelvic walls. It continuous superiorly to form its upper free margin but separated inferiorly to cover the pelvic floor. The ovary attached to its posterior layer by the mesovarium

Contents of broad ligament:

  • Uterine tube in its upper free border
  • Round ligament of the ovary
  • Round ligament of the uterus
  • Uterine vessels, nerves, and lymphatics
  • Ovarian vessels, nerves, and lymphatics
  • Epoophoron represents remains of mesonephros
  • Paroophoron mesonephric remnant

Blood Supply

  • Arteries
    Mainly from the uterine arteries (from internal iliac artery)
    Ovarian artery
  • Veins
    Venous plexus drains through uterine, ovarian and vaginal veins into internal iliac vein
  • Lymphatic drainage; fundus of the uterus to lumbar, body of uterus to external iliac, Cervix to internal iliac

Nerve Supply

  • Sympathetic – T12, L1
  • Parasympathetic – S 2, 3, 4