Pelvic Cavity LO4
4. Understand the gross anatomy and anatomical relationships of the female pelvic reproductive viscera & genital tract, associated fascial specializations, peritoneal specializations, and pertinent neurovasculature.
The female reproductive viscera consist of the uterus, uterine (Fallopian) tubes, ovaries, vagina, and associated mesenteries and ligaments. The uterus is positioned in an intermediate position between the bladder and rectum. The uterine (Fallopian) tubes and ovaries are superolaterally positioned to the uterus. The vagina is continuous inferiorly with the cervix of the uterus, and communicates with the external environment via the vaginal orifice in the vestibule of the vagina.
The uterus is a pyriform (pear-shaped), distensible organ which may shelter a developing embryo & fetus until parturition. The uterus is structurally comprised of two parts: the muscular, ‘upper’ two-thirds is the body, and the lower, fibrous third is the cervix. The most anterior portion of the body of the uterus is the fundus. Uterine (Fallopian) tubes are laterally continuous with the body of the uterus, and serve as a pathway for oocytes (and their ontogenetic derivatives) from the ovary to the uterine cavity. The uterine a. is the dominant source of blood to the uterus, but there are anastomoses with the ovarian & vaginal aa. The uterus is innervated by the uterovaginal (autonomic) plexus derived from the inferior hypogastric plexus.
Fertilization of an oocyte typically occurs in the ampulla of the uterine tube, whereas implantation of the zygote occurs in the uterus. Implantation and subsequent gestation occurring outside the uterus is known as ectopic pregnancy. Typically, ectopic pregnancies occur in the uterine tube, but they may occur in the abdominopelvic cavity as well.
Tubal ligation ("tubes tied") is a surgical means of female sterilization where the uterine tubes are ligated, incised, clamped, or occluded to prevent the passage of oocytes to the uterus.
The uterus and uterine tubes may be examined with hysterosalpingography (HSG), a method of fluoroscopic imaging that evaluates the lumen of the uterine tube and uterus.
Hysterectomy is the surgical removal of the uterus. Oophorectomy is the surgical removal of an ovary.
The broad ligament of uterus is composed of two layers of peritoneum and serves to divide the true pelvis of females into an anterior part (containing the bladder) and a posterior part (containing the rectum), in addition to attaching the uterus to the lateral pelvic walls. The uterine (Fallopian) tubes are suspended within the superior-most portions of the broad ligament (mesosalpinx), while the ovaries are posteriorly oriented and associated with the mesovarium. Superolaterally, the broad ligament is attached to the suspensory (infundibulopelvic, or IP) ligament of ovary, which contains the ovarian neurovasculature. The inferior and largest portion of the broad ligament (mesometrium) is continuous with the parietal peritoneum of the pelvis. The body of the uterus is subperiteoneal, and located between the rectum and urinary bladder. The vesico-uterine pouch is the inferior-most extension of peritoneum between the bladder and the uterus. The recto-uterine pouch is comparatively deeper and is located between the uterus/vagina and the rectum. The posterior fornix of the vagina is in contact with the recto-uterine pouch and offers access to the peritoneal cavity.
Components of the broad ligament:
Other, non-peritoneal, condensations of endopelvic fascia (viscera fascia/connective tissues that connect pelvic organs to the pelvic wall) are found within the pelvic cavity, supporting viscera. Two major aggregates include the hypogastric sheath and the perimetrium. The hypogastric sheath connects the lateral pelvic wall to pelvic viscera. There are three main components of the hypogastric sheath:
The endopelvic fascia associated with the uterus (inclusive of the transverse cervical ligament) is known as the perimetrium. A visceral peritoneum derivative, the perimetrium, extends inferiorly, and is known as the paracolpium when associated with the vagina. The paracolpium transmits the vaginal aa.
Several other important pelvic ligaments are noteworthy for the anatomical and clinical significance. These include:
The vagina is a muscular passage from the cervix of the uterus to the vestibule of the vagina. The vagina is posteriorly adjacent to the base of the urinary bladder and urethra, and is anteriorly adjacent to the rectum. The vaginal a. is the dominant source of blood to the vagina. The proximal (upper) two-thirds of the vagina is innervated by the uterovaginal (autonomic) plexus, whereas the distal (lower) third of the vagina is innervated by the deep branch of the perineal n. (from pudendal n.). Proximally, the vaginal fornix surrounds the protrusion of the cervix into the vagina. The vaginal fornix may be conceptually dived into anterior, lateral, and posterior parts, with the posterior vaginal fornix being most clinically significant, as it offers access to the recto-uterine pouch.