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A N A T O M Y FOR DIAGNOSTIC I M A G I N G
THE FEMALE REPRODUCTIVE TRACT (Figs 6.19-6.26)
Lymph drainage
The vagina (Fig. 6.19; see Fig. 6.21)
The upper two-thirds drain to internal and external iliac nodes. The lower third drains to superficial inguinal nodes.
The vagina is an extraperitoneal structure. This muscular canal extends from the uterus to the vestibule, opening between the labia minora behind the urethra and clitoris. It has a rectangular shape, being flattened from front to back. Superiorly the cervix of the uterus projects into its anterior wall at an acute angle. The cervix invaginates the upper vagina and arbitrarily divides it into a shallow anterior and deep posterior and lateral recesses or fornices. The ureters pass medially above the lateral fornices. In front of the vagina is the base of the bladder and the urethra. Behind the upper vagina is the pouch of Douglas, containing loops of bowel. Below and behind this peritoneal reflection is the rectum. On either side are the levator ani muscles and the pelvic fascia, which are slung around the vagina and rectum, supporting these structures. The vagina traverses levator ani and the urogenital diaphragm, which have a sphincter-like action. The levator muscles insert into a fibromuscular node called the perineal body, which lies between the lower vagina and the anal canal. Blood supply Vaginal branches of the internal iliac and the uterine arteries supply the vagina. Venous drainage is via a plexus on its lateral walls to the internal iliac vein.
Fig. 6 . 1 9
Female pelvis: sagittal section showing pelvic floor.
The uterus (Figs 6.19-6.21) The uterus is extraperitoneal. It is a pear-shaped muscular organ lying between the bladder and rectum. It has a fundus, a body and a cervix. It lies on the posterosuperior surface of the bladder with its cervix projecting into the anterior wall of the upper vagina. The cavity of the uterus is triangular in coronal section, but its anterior and posterior walls are apposed, giving it a slit-like appearance in the sagittal plane. The uterine tubes open into the cornua of the uterus superolaterally. The uterus leads to the vagina via the cervical canal. Just above the cervical canal the uterine cavity narrows to an isthmus. The internal os is at the upper end of the cervical canal and the external os at its lower end. The inner lining of the uterus is the endometrium, which undergoes cyclical changes of proliferation and desquamation in the premenopausal female. Peritoneum covers the fundus, body, cervix and upper part of the vagina posteriorly. From here it is reflected on to the anterior surface of the rectum, forming the pouch of Douglas. Anteriorly, the peritoneum is reflected from the upper part of the body to the superior surface of the bladder. On either side of the uterus the peritoneum is reflected to the lateral pelvic walls covering the fallopian tubes. The
