Female reproductive organs

Vagina

The vagina is the outermost internal female sex organ. It extends from the uterus to the vulva (external genitalia). Functionally, it facilitates menstruation, sexual intercourse and childbirth. The vagina is located posterior to the urinary bladder and urethra, and anterior to the rectum.

The upper end of the vagina is attached to the cervix of the uterus. These structures form a pouch (vaginal fornix) which has anterior, posterior, and lateral parts. The lower end of the vagina (vaginal orifice) opens into the vaginal vestibule just behind the urethral orifice. The vaginal orifice may be partially covered with a membrane called hymen.

The vagina is supplied by branches of the internal iliac artery; uterine, vaginal and internal pudendal arteries. Venous drainage of the vagina is provided by the vaginal veins which flow into the internal iliac veins. Nervous supply is derived from the: 

• Inferior hypogastric plexus via the uterovaginal plexus - the sympathetic and parasympathetic fibers are conveyed by the thoracolumbar (T12-L1) and pelvic splanchnic nerves (S2-S4), respectively.
• Pudendal nerve via the deep perineal nerve.  

Lymph is drained from the vagina into the iliac and superficial inguinal lymph nodes.

Uterus

The uterus (womb) is a hollow muscular organ located deep within the pelvic cavity. Anterior to the rectum and posterosuperiorly to the urinary bladder, the uterus normally sits in a position of anteversion and anteflexion. The endometrial lining of the uterus proliferates each month in preparation for embryo implantation. If fertilization occurs, the uterus acts to house the growing fetus and its placenta. If pregnancy does not occur, the endometrial lining is shed during menstruation.

The uterus is divided into three parts:

• Body (corpus) - the main part of the uterus, connected to the uterine (fallopian) tubes via the uterine horns. The body has a base (fundus) and an internal chamber (uterine cavity). 
• Isthmus - the constricted part of the uterus, located between the body and the cervix.
• Cervix - the inferior portion of the uterus. It consists of two parts (supravaginal, vaginal), two openings (internal os, external os) and a cervical canal.

The uterus is partially covered by peritoneum. As it reflects from the uterus to the rectum and urinary bladder, two folds are formed: the rectouterine pouch (of Douglas) and the vesicouterine pouch, respectively. Several peritoneal ligaments support the uterus and hold it in place: broad ligament, round ligament, cardinal ligament, uterosacral ligament and pubocervical ligament.

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The uterus is supplied mainly by the uterine artery which arises from the internal iliac artery. The superior branch of the uterine artery supplies the body and fundus, while the inferior branch supplies the cervix. The venous blood of the uterus is drained via the uterine venous plexus into the internal iliac vein.

The uterus receives innervation from the inferior hypogastric plexus via the uterovaginal nervous plexus, similar to the vagina. Lymphatic drainage of the uterus is into the lumbar, superficial inguinal, iliac (internal, external) and sacral lymph nodes.

Ovaries

The ovaries are bilateral female gonads and the equivalent of the male testes. They release the ovum (egg) for the purpose of fertilization. In addition, they act as endocrine glands, secreting various hormones necessary for fertility, menstruation and sexual maturation of the female.

Each ovary is located in the ovarian fossa of the true pelvis, adjacent to the uterus and below the fallopian tubes. The ovary contains four surfaces (anterior, posterior, medial, lateral) and two poles (superior, inferior). It is held in its normal position by several paired ligaments: suspensory ligament of the ovary, proper ovarian ligaments (ligament of ovary) and mesovarium. 

Ovaries receive arterial supply from the ovarian arteries, which arise from the abdominal aorta. These blood vessels reach the gonads by traveling within the suspensory ligaments. 

Venous blood of the ovaries is drained by the pampiniform plexus. These veins later coalesce and form the ovarian veins. The right ovarian vein drains into the inferior vena cava, whereas the left ovarian vein flows into the left renal vein. The ovaries are innervated by the ovarian nervous plexus which receives fibers from the aortic, renal and hypogastric (superior, inferior) plexuses. Sympathetic fibers are derived from the lesser splanchnic nerves (T10-T11). Parasympathetic innervation arises from the pelvic splanchnic nerves (S2-S4). Lumbar lymph nodes are responsible for lymphatic drainage of the ovaries.

Uterine tubes

The uterine (fallopian) tubes are bilateral muscular organs that extend from the uterine horns to the superior poles of the ovaries. The fallopian tubes represent the usual site for ovum fertilization. They also transport the resulting zygote into the uterus for implantation.

The uterine tubes are intraperitoneal organs, covered completely by a part of the broad ligament of the uterus called the mesosalpinx. They consist of four main parts: 

• Infundibulum - the distal part of the uterine tube that opens into the peritoneal cavity via the abdominal ostium. The infundibulum contains finger-like projections called fimbriae which extend over the medial surface of the ovaries.
• Ampulla - is the longest and widest part of the uterine tube. It is the most common site of fertilization.
• Isthmus - is the narrowest part of the uterine tube
• Intramural (uterine) part - it communicates directly with the uterine cavity via the uterine ostium. 

The uterine tube receives arterial supply from the uterine and ovarian arteries. The former is a branch of the internal iliac artery, and the latter arises from the abdominal aorta. Venous drainage of the uterine tubes is mediated by the tubal veins. These drain into the uterine and pampiniform venous plexuses.

The uterine tube receives sympathetic innervation from the superior hypogastric plexus (T10-L2) via the hypogastric nerve. Parasympathetic innervation stems from the pelvic splanchnic nerves and the vagus nerve. Lymph is drained from the uterine tubes to the para-aortic, internal iliac and inguinal nodes.

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Mons pubis

The mons pubis is a mass of subcutaneous adipose tissue located anterior to the pubic symphysis. The skin overlying the mons pubis is covered with a triangular patch of pubic hair.

Labia majora

Labia majora are two longitudinal skin folds covered with pubic hair. They are the most lateral part of the vulva, extending from the mons pubis to the perineum. The cleft between the labia majora is called the pudendal cleft. It contains the labia minora and the vestibule. The two labia majora merge anteriorly (anterior commissure) and posteriorly (posterior commissure). The labia majora are homologous to the scrotum of the male.

Labia minora

Labia minora are two longitudinal, thin and hairless skin folds found between the labia majora. They surround the vaginal vestibule and its urethral and vaginal orifices. The labia minora contribute to the formation of the prepuce and frenulum of the clitoris.

Clitoris

The clitoris is an erectile organ responsible for sexual sensations. It is analogous to the male penis. Located at the most superior part of the vulvar vestibule, the clitoris is surrounded by the anterior part of the labia minora. It has three parts: root, body and glans. The body consists of two corpora cavernosa and two attachment points (crura). 

Vestibule

The region between the labia minora is called the vestibule. This perineal area contains the vaginal orifice, opening of the female urethra and the openings for the excretory ducts of the greater and lesser vestibular glands.

Vestibular glands

There are three types of glands that open into the vestibule:

• The greater vestibular (Bartholin's) glands are found on each side of the vestibule. They are homologous to the bulbourethral glands in the male and serve to lubricate the vulva during sexual intercourse
• The lesser vestibular glands are located between the urethral and vaginal orifices. These glands are homologous to the male prostate.

Vestibular bulb

The bulbs of vestibule are a pair of subcutaneous erectile tissues analogous to the penile bulb and corpus spongiosum in males. They extend on each side of the vestibule and join in front of the urethral orifices.

Blood supply and innervation

The external genitalia are supplied by the pudendal arteries (internal, external) which are branches of the internal iliac and femoral arteries, respectively. Venous drainage is mediated by the internal and external pudendal veins.

The anterior aspect of the vulva receives sensory innervation from the ilioinguinal nerve and genitofemoral nerve. The posterior aspect is supplied by the pudendal nerve and the posterior cutaneous nerve of the thigh. The bulb of the vestibule and the clitoris receive parasympathetic innervation from the uterovaginal nerve plexus.Lymph from the external genitalia is drained by the superficial and deep inguinal lymph nodes, or directly into the internal iliac lymph nodes.