Female Reproductive Tract (Anatomy)
Key functions of the reproductive system:
It facilitates sexual maturation of individuals and sexual reproduction of offspring.
In the female, this includes the production of ova (aka, eggs) and their transport through the reproductive tract (where fertilization occurs).
Houses and support a developing fetus.
Key organizational features of the reproductive system:
Reproductive structures are classified as either primary or accessory (aka, secondary):
- The primary structures are referred to as gonads, which produce gametes (aka, sex cells).
- In females, the primary structures are the ovaries, which produce ova (singular = ovum) and hormones.
- The accessory structures are the organs, ducts, and glands that facilitate transport of the ova.
- Oocytes become ova
- Ova pass through them from the ovaries to the uterus; fertilization is most likely to occur within the uterine tubes.
- Fimbriae are the finger-like projections that overlie, but do not attach to, the ovary (with the exception of a single ovarian fimbria, which does attach to the ovary).
- Aka, womb
- Undergoes cyclical changes in response to ovarian hormones.
- Lies posterior and superior to the urinary bladder
- Cervix is the narrow inferior region of the uterus.
Vagina
- A muscular tube that facilitates passage of menstrual fluid, the penis, and semen during intercourse, and the fetus and placenta, during parturition (childbirth).
- Fornix is the recess created by the projection of the cervix into the vagina. These "vaults" hold ejaculated semen near the cervical entrance of the uterus.
- Vaginal orifice is its inferior opening; recall that the vagina opens posterior to the external urethral orifice, within the vestibule of the vagina.
- Vestibule of the vagina is bound by the labia minora.
Connective tissues
Anchor and support the reductive organs within the pelvis.
Broad ligament
- A double-layered sheet of peritoneum that extends laterally from the uterus
- Subdivisions:
- The mesosalpinx is the superior part of the broad ligament that wraps over the uterine tubes;
- The mesovarium is a posterior extension of the broad ligament that attaches to the ovaries as surface epithelium;
- The mesometrium is the largest part of the broad ligament; it extends from the uterus to the pelvic walls.
Ovarian ligament
- Attaches the ovary to the outer surface of the uterus; it is enclosed by the mesovarium.
Round ligament of the uterus
- Is continuous with the ovarian ligament, and exits the pelvis anteriorly via the inguinal canal to terminate within the labia majora.
Suspensory ligament of the ovary
- Aka, infundibulopelvic ligament
- A peritoneal fold that extends laterally from the ovary; neurovascular structures that travel within it.
Clinical correlations:
- Ectopic pregnancy refers to the implantation of an embryo outside of the uterus, most commonly occur within the uterine tubes, but potentially in the ovary, abdomen, or pelvis. Treatment is required because ectopic pregnancies can be life-threatening.
- Endometriosis occurs when endometrial tissues from the uterine lining are displaced and implanted on the surfaces of the abdominopelvic organs. These tissues remain responsive to hormonal signals, and can cause significant pain and scarring. Treatments, including hormonal contraceptives, can limit the activity of lesions and reduce pain.
Details of the 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.