The Anatomy of the Female Pelvis
The female pelvic organs include the egg-producing ovaries and the uterine tubes that carry the eggs into the uterus for potential fertilization by male sperm. They also include the vagina, which is the entryway to the uterus.
The female urethra
The female urethra runs from the internal urethral orifice of the urinary bladder, anterior to the vagina, to the external urethral orifice in the vulva. Two paraurethral glands open into the urethra near the external urethral orifice.
The urethra is innervated by the vesical plexus as well as the pudendal nerve. The urethra receives blood from the internal pudendal and vaginal arteries and returns blood through their accompanying veins. Lymph drains into the internal iliac and sacral nodes.
The uterus and the vagina
The uterus is a pear-shaped hollow organ with muscular walls. Its function is to nourish a fertilized ovum. In a nonpregnant female, it lies on the urinary bladder. The fundus lies above the entrance of the uterine tube; the body is the part below. The cervix is the narrow part that protrudes into the vagina. It has a cervical canal, which opens into the vagina through the external os, which is the opening of the uterus.
The external os is circular in a woman who hasn’t given birth, but after childbirth, the external os becomes a transverse slit.
The walls of the uterus consist of three layers.
Perimetrium: A fascial layer
Myometrium: A thick layer made up of smooth muscle and connective tissue
Endometrium: Lines the body of the uterus and is the part of the uterus that’s involved with the menstrual cycle
Uterine fibroids are benign (noncancerous) tumors that grow in the lining of the uterus. The cause isn’t known, but it appears to be linked with the female hormone, estrogen. If they’re small, there’s no problem, but if they grow into larger masses, they can cause longer and heavier menstrual periods, pain, and a feeling of fullness in the pelvis. Treatment may include birth-control pills to regulate the hormones, intrauterine devices to reduce bleeding, iron supplements to prevent anemia, nonsteroidal anti-inflammatory medications for pain relief, and surgery if necessary for large and troublesome fibroids.
The uterus is supported by several ligaments, including the round ligament (attaches to the uterus near the junction of the uterine tube and runs through the inguinal canal to the labia majora), the ligament of the ovary (attaches to the uterus just posterior and inferior to the uterine tube), the broad ligament (extends from the sides of the uterus to the lateral walls and floor of the pelvis), the cardinal ligament (runs from the cervix to the lateral wall), and the suspensory ligament (attaches to the ovary).
Nerve supply comes from the inferior hypogastric plexuses. The uterus receives blood flow from the uterine artery and returns blood via the uterine vein. Lymph drains into the para-aortic, internal iliac, external iliac, and superficial inguinal nodes.
The vagina is a mostly muscular tube that extends from the uterus to an external opening surrounded by the labia and vulva. The part of the vagina that surrounds the cervix is divided into four fornices: anterior, posterior, and left and right lateral. The vagina is also known as the birth canal, because the baby passes through the vagina during birth. It also allows excretion of menstrual flow. Nerve supply comes from the inferior hypogastric plexus. Blood flow comes from the vaginal artery and vaginal veins. Lymph drains into the external and internal iliac nodes and the superficial inguinal nodes.
The uterine tubes and the ovaries
The uterine tubes lie between the ovaries and uterus, in the broad ligament. Each tube starts with the funnel-shaped infundibulum, which has fimbriae, finger-like projections that lie over the ovary. The ampulla is the widest part of the tube, which narrows to form the isthmus. The intramural part opens into the uterine wall.
An ectopic pregnancy occurs when the fertilized ovum implants outside of the uterus, usually within the walls of the uterine tubes. Symptoms include abnormal vaginal bleeding, amenorrhea, breast tenderness, lower back pain, and pain or pelvic cramps. The pregnancy cannot continue, and the implanted cells must be removed to save the woman’s life.
The ovaries are two oval-shaped organs attached to the broad ligament. The suspensory ligament of the ovary conveys blood vessels and nerves to the ovaries, while the round ligament runs between the uterus and the ovaries.
The nerve supply for the uterine tubes comes from the inferior hypogastric plexuses. The nerve supply to the ovaries comes from the aortic plexus. The uterine tubes and ovaries receive blood flow from the uterine and ovarian arteries, and they return blood via veins of the same names. Lymph drains into the internal iliac and para-aortic nodes.