Female reproductive system and breast

The female reproductive system is composed of external and internal genitalia. The female internal genitalia consist of the vagina, uterus and cervix, fallopian tubes and ovaries. The female external genitalia is called the vulva. It consists of the mons pubis, labia majora and minora, hymen, clitoris, vestibule, urethra, Skene glands, Bartholin’s glands and vestibular bulbs. The labia majora cover the labia minora. The clitoris is an erectile tissue located within the glans clitoris, a fold formed by the joining of the two labia minora anteriorly. It has a rich nerve supply and is innervated by the dorsal nerve of the clitoris, a branch of the pudendal nerve. The urethra opens just anterior to the vaginal opening, in the vestibule. Skene’s glands also called as lesser vestibular glands or paraurethral glands are located along the anterior wall of the vagina and open on either side of the urethral opening or urethral meatus. They produce female ejaculate and are analogous to the male prostate gland.

Vagina

It is a fibromuscular canal that leads to the cervix on one end. It is located anterior to the rectum and posterior to the bladder and is positioned at a 90 degree angle to the uterus. It has four walls, namely, anterior and posterior and two lateral walls and a superiorly located vaginal fornix that connects to the cervix. Typically, the vaginal walls are collapsed, looking like the letter H in cross section. The walls have an inner mucosa lined by nonkeratinized stratified squamous epithelium, a middle smooth muscle layer and external adventitious layer. It shows numerous transverse folds called rugae which allow the vagina to expand during childbirth. The lower one-third of the vagina is fused with the perineal body. The pelvic diaphragm, sphincter urethrae and transverse peroneus muscles and the perineal membrane support the vagina. In the adult female, the vagina is rich in commensal Lactobacilli which help to maintain the vaginal pH below 4.5 (acidic) by the production of lactic acid. This has important antimicrobial properties. Cervical glands, Bartholin and Skene’s glands all help lubricate the vagina. Under the effect of estrogen such as at the onset of puberty, the epithelial cells accumulate glycogen and there is a proliferation of cells in the basal and parabasal layers. It is supplied by the vaginal artery which is a branch of the anterior division of the internal iliac artery. Sensory innervation is of lower part is by the pudendal nerve and the upper part is by the autonomic nervous system in the pelvic plexus. Lymphatic drainage from the lower third is to superficial inguinal nodes, middle third drains to common and internal iliac nodes and upper third drains to external iliac nodes.

Uterus and Cervix

The uterus is a muscular organ that sits in the pelvis. It is 2x3” in the non pregnant stage. It can be divided into the larger body, the lower cervix, a narrow isthmus connecting the body (corpus) and cervix and an upper, dome shaped fundus that lies above the level of opening of the fallopian tubes. It sits in the pelvis in an anteverted and anteflexed position. Version refers to the angle between the cervix and vagina, anteverted means bent forward. Flexion refers to the angle between the uterine body and cervix. Anteflexed meaning bent forward. The bladder lies anterior and the rectum is posterior to the uterus.

The cervix is a 3-5 cms long, cylindrical structure, lying between the internal os and external os. It’s cavity is called the endocervical canal. The epithelium lining the endocervical canal is called endocervix and it is simple columnar. It is rich in mucus producing glands. The part of the cervix that projects into the vagina is lined by ectocervix. It is a non-keratinized, stratified squamous epithelium in the prepubertal stage. At puberty, the simple columnar epithelium of the endocervix migrates into the ectocervix. As a result of exposure to the acidic vaginal milieu, the columnar epithelium shows squamous metaplasia in an area called the transformation zone. It is clinically important as it is the site of squamous cell cancers of the cervix.

Histologically, the uterus is made of three layers - the inner endometrium, middle myometrium and outer perimetrium. The endometrium is lined by simple columnar epithelium which invaginates into the stroma underneath to form the endometrial glands. It has a basal layer which is responsible for regeneration of the epithelium following menstruation. The functional layer is the one that is sloughed off during menses. Myometrium is a thick, smooth muscle layer while perimetrium is the outer connective tissue layer. Muscle fibres in the myometrial layer run horizontally, vertically and diagonally.

The uterus is supplied by the uterine arteries which are branches of the anterior division of the internal iliac arteries. It lies in the cardinal ligament. It divides into ascending and descending branches. The tortuous ascending branch courses up in the broad ligament and anastomoses with the ovarian artery. The descending branch supplies the cervix and vagina. The uterine artery gives arcuate, radial, spiral and basal artery branches in the myometrium. The spiral artery supplies the endometrium, decidua and placenta. Estrogen causes an increase in size and number of the spiral arteries.

Ligaments of the Uterus

The uterus is supported in the pelvis by several ligaments. Broad ligament is a fold of peritoneum that extends laterally from the uterus to connect to the lateral pelvic walls. It is composed of three parts - mesovarium, mesosalpinx and mesometrium. The mesovarium extends to the hilum of the ovaries. The mesosalpinx is related to the fallopian or uterine tubes. The mesometrium is related to the uterus. The broad ligament contains the round ligament, the fallopian tube, blood vessels, lymphatics and nerve fibres. The superior margin of the broad ligament is called the round ligament. It is about 10-12 cm long. On one end it is attached to the cornu of the uterus (upper and lateral area, one on each side), from there it travels through the deep inguinal ring, inguinal canal and ends at the labia majora and mons pubis. Sampson’s artery is a branch of the uterine artery which runs with the round ligament. It must be ligated during hysterectomy. The cardinal ligament forms the inferior border of the broad ligament. It is attached to lateral sides of the cervix. The pubocervical ligament runs from the posterior surface of the symphysis pubis to the cervix. Rectouterine or uterosacral ligaments stretch from the cervix to the sacrum.