The female reproductive system is a complicated but fascinating subject. It has the capability to function intimately with nearly every other body system for the purpose of reproduction.
The female reproductive organs can be subdivided into the internal and external genitalia (see the images below). The internal genitalia are those organs that are within the true pelvis. These include the vagina, uterus, cervix, uterine tubes (oviducts or fallopian tubes), and ovaries. The external genitalia lie outside the true pelvis. These include the perineum, mons pubis, clitoris, urethral (urinary) meatus, labia majora and minora, vestibule, greater vestibular (Bartholin) glands, Skene glands, and periurethral area
External Genitalia
The vulva, also known as the pudendum, is a term used to describe those external organs that may be visible in the perineal area (see the images below). The vulva consists of the following organs: mons pubis, labia minora and majora, hymen, clitoris, vestibule, urethra, Skene glands, greater vestibular (Bartholin) glands, and vestibular bulbs. [1, 2, 3] The boundaries include the mons pubis anteriorly, the rectum posteriorly, and the genitocrural folds (thigh folds) laterally.
External female genitalia.
Deeper view of external structures.
Mons pubis
The mons pubis is the rounded portion of the vulva where sexual hair development occurs at the time of puberty. This area may be described as directly anterosuperior to the pubic symphysis.
Labia
The labia majora are 2 large, longitudinal folds of adipose and fibrous tissue. They vary in size and distribution from female to female, and the size is dependent upon adipose content. They extend from the mons anteriorly to the perineal body posteriorly. The labia majora have hair follicles.
The labia minora, also known as nymphae, are 2 small cutaneous folds that are found between the labia majora and the introitus or vaginal vestibule. Anteriorly, the labia minora join to form the frenulum of the clitoris.
Histologically, the vulva is predominantly keratinized, stratified squamous epithelium. [4] The labia majora are composed of both sebaceous and sweat glands; the labia minora are made up of dense connective tissue with erectile tissue and elastic fibers.
The hymen consists of fibrous tissue with a few small blood vessels and is covered by stratified squamous epithelium. The body of the clitoris is composed of 2 channels of vessels and nerve endings that function as erectile tissue, the corpora cavernosa.
The mucosa of the proximal two-thirds of the urethra is composed of stratified transitional epithelium similar to that of the urinary bladder. The distal one-third is composed of stratified squamous epithelium. The greater vestibular glands are mostly made up of cuboidal epithelium, with the ducts lined by transitional epithelium.
The vagina has 3 layers. The first layer is the mucosa, the epithelium of which is composed of stratified squamous cells that contain a small amount of keratin. The lamina propria is composed of loose connective tissue that has a vast amount of elastic fibers, giving the vagina its capability to distend. The second layer is muscular, mainly smooth muscle. The final layer is the adventitia, which is also rich in elastic fibers. A large plexus of blood vessels is also present. [4]
The uterine corpus has 3 layers, from innermost to outermost: endometrium, myometrium, and serosa. The endometrium is composed of cells resembling embryonic connective tissue, with scant amounts of cytoplasm and large nuclei. It can be subdivided into 2 more layers: the inner stratum basale and the outer stratum functionale. The stratum functionale is the layer of the endometrium that responds to hormonal stimulation. The myometrium is composed of 3 layers of smooth muscle. The serosa is a continuation of the visceral peritoneum. [4]
Most of the cervix is composed of collagenous connective tissue, smooth muscle, and mucopolysaccharide ground substance. The endocervical canal is rich in mucous glands and is primarily columnar epithelium. The external portion of the cervix that lies within the vagina is composed of stratified squamous epithelium.
The area surrounding the external os is termed the transformation zone, which is the transition point between squamous cells externally and columnar cells of the endocervical canal. The transformation zone is the area where cervical cell changes (ie, dysplasia) can occur. Most cell changes are picked up during a Papanicolaou smear, the screening test for cervical cancer. [4]
Internally, the uterine tubes have many folds, or plicae, which are most evident in the ampulla. Within the mucosa of the uterine tubes, 3 different dell types exist: columnar ciliated epithelial cells (25%), secretory cells (60%), and narrow peg cells (< 10%). A muscular layer of smooth muscle surrounds the mucosa. [4]
Variations of female reproductive anatomy often stem from dysfunction during development in utero. They can also be caused by genetic changes or teratogenic effects.
Clitoromegaly, imperforate hymen (see the image below), labial fusion, and vaginal agenesis are the most common variants of the external genitalia. Performing a thorough physical examination of newborns to detect these changes is important.
Imperforate hymen.
Internally, the most common variants include vaginal septa, arcuate uterus, bicornuate uterus, didelphic uterus (see the image below), unicornuate uterus, and septate uterus. Uterine anomalies are most frequently diagnosed by performing hysterosalpingography, a radiologic study in which dye is injected into the uterine cavity to visualize any abnormalities. Uterine anomalies are often detected during evaluation for infertility. These conditions are commonly diagnosed at the time of cesarean section.