›

Uterus & Uterine Tubes

Notes

Uterus & Uterine Tubes

Ovarian hormones regulate the functioning of the uterine tubes and uterus.

Uterine tubes

3 tunics of the uterine tubes:

  • Serosa comprises the outermost layer.
  • Muscularis is the muscular middle layer.
  • Mucosa comprises ciliated epithelia; it faces the lumen of the tube.

Clinical Correlation:

Ectopic Pregnancy

These tunics facilitate fertilization via:

  • Peristaltic contractions and cilia that transport ova and sperm.
  • Mucosal secretions that initiate the final stages of sperm maturation.

Tube Segments

  • Uterine (aka, intramural) segment arises within the uterus; it regulates the passage of sperm and bacteria into the uterine tubes.
  • Isthmus comprises a relatively thick muscularis layer; sperm are held here for about 24 hours, while uterine tube secretions stimulate capacitation, which is required for fertilization.
  • Ampulla is the thin-walled, dilated portion; the ampulla is the most common site of fertilization (joining of ovum and sperm).
  • Infundibulum is the wide "trumpet-shaped" lateral end of the uterine tube.
  • Fimbriae are the terminal finger-like projections.
  • The fimbriae "catch" the ovulated ova from the ovaries as they burst into this space.
  • Ova are released into the peritoneal cavity and (usually) swept up by the fimbriae.
  • Abdominal ostium is the opening of the uterine tube to the peritoneal cavity.

Uterus

3 layers of the uterine wall:

  • Perimetrium is the outermost layer.
  • Myometrium comprises interweaving bundles of smooth muscle that contract during orgasm and to expel menstrual fluid during menstruation and the fetus and placenta during childbirth.
  • Endometrium is the dynamic innermost layer that undergoes periods of regeneration, differentiation, and shedding over the course of the menstrual cycle.
    • When conditions are favorable, a fertilized ovum will implant into the endometrium, and menstruation will not occur.

Regions of the uterus:

  • Uterine cavity is the lumen of the uterus.
  • Uterine horns are continuous with the uterine tubes.
  • Body comprises the majority of the uterus.
  • Superiorly is the fundus, which is the region above to the uterine cavity.
  • Inferiorly is the isthmus, which is where the uterus constricts.
  • Cervix is most inferior region of uterus.
    • Internal os is the opening between the cervix and the isthmus.
    • External os is the opening between the cervix and the vagina.
    • Cervical canal is between the internal and external os.
    • Glands within the cervical canal secrete mucus, which changes over the course of the menstrual cycle to allow or block the entry of sperm into the uterus.

Clinical correlations:

  • Infections (such as pelvic inflammatory disease) can spread from the uterine tubes to the peritoneal cavity. Agglutination of the fimbriae can close off the opening and prevent the spread of infection, but, because the uterine tube is effectively sealed off, fertility is impaired.
  • Cervical cancer is most commonly caused by HPV (human papillomavirus); thus, HPV vaccinations help prevent cervical cancer.