Uterine Cavity

The uterine cavity is the hollow interior space of the uterus, designed to support embryo implantation and fetal development. It lies within the body of the uterus and communicates with the fallopian tubes at the uterine horns and with the cervical canal inferiorly through the internal os. Though small in the non-pregnant state, the cavity is highly distensible and undergoes dramatic expansion during pregnancy. The shape, dimensions, and lining of the cavity are all optimized for its reproductive functions, including menstrual shedding, sperm transport, fertilization support, and gestation.

Structure

The uterine cavity is a narrow, flattened, slit-like space in the non-pregnant state. Its walls are formed by the thick muscular myometrium and are internally lined by endometrium, which undergoes cyclical changes during the menstrual cycle. The cavity has a triangular shape when viewed in coronal section and communicates with the fallopian tubes laterally and the cervical canal inferiorly.

• Shape (non-pregnant): Inverted triangle
• Walls:
  • Anterior and posterior: Formed by myometrium and endometrium
  • Lateral angles: Uterine horns (open into fallopian tubes)
  • Inferior boundary: Internal os of the cervix

Layers of the Uterine Wall Surrounding the Cavity

1. Endometrium: Mucosal lining, responsive to hormonal changes
   • Stratum functionalis: Shed during menstruation
   • Stratum basalis: Regenerates the functionalis
2. Myometrium: Thick smooth muscle layer, responsible for contractions
3. Perimetrium: Outer serous layer (peritoneal covering)

Location

The uterine cavity is located centrally within the body of the uterus in the female pelvis. It is situated between the fundus and the internal os of the cervix. The cavity is oriented in an anteroposterior plane and is normally anteverted and anteflexed in alignment with the vagina and cervix.

Function

• Implantation Site: Provides the environment for blastocyst attachment and implantation
• Menstruation: Endometrial shedding occurs when implantation does not occur
• Gestation: Expands to accommodate a growing fetus during pregnancy
• Sperm Transport: Acts as a conduit for sperm from cervix to fallopian tubes
• Support for Embryo/Fetus: Secretes nutrients and forms the maternal part of the placenta

Blood Supply

• Arterial: Uterine artery (branch of internal iliac artery) — via arcuate, radial, and spiral arteries
• Venous: Uterine venous plexus → internal iliac vein

Lymphatic Drainage

• Fundus and upper cavity: Para-aortic and superficial inguinal nodes
• Lower cavity: Internal iliac nodes

Innervation

• Sympathetic: T10–L2 (via hypogastric plexus)
• Parasympathetic: S2–S4 (via pelvic splanchnic nerves)
• Afferent fibers: Travel via sympathetic pathways → referred pain to lower abdomen

Embryological Development

• Formed from the fusion of the paired paramesonephric (Müllerian) ducts
• Failure of fusion may lead to anomalies such as septate or bicornuate uterus

Clinical Significance

• Endometrial hyperplasia: Abnormal thickening of endometrium due to unopposed estrogen
• Endometrial carcinoma: Most common gynecologic malignancy; originates in uterine cavity lining
• Intrauterine adhesions (Asherman’s syndrome): Scar tissue in the cavity causing infertility or amenorrhea
• Submucosal fibroids: Benign growths that project into and distort the cavity; affect fertility
• Uterine septum: Congenital anomaly of the uterine cavity due to incomplete Müllerian duct resorption