The Female Reproductive System

The female reproductive system consists of the ovaries, uterine tubes, the uterus, vagina and external organs collectively called the vulva. The mammary glands are also considered a part of the reproductive system.

The ovaries

The ovaries are the female gonads. They are the size of an unshelled almonds and have the same embryonic origins as testes. The ovaries produce gametes and hormones. The ovaries are found on either side of the uterus, in the superior side of the pelvic cavity. It is suspended in place by a series of ligaments. This includes the mesovarium derived from the broad ligament of the uterus, the ovarian ligament and the suspensory ligament. Each ovary contains a hilum where vessels enter, and where the mesovarium attatches.

Ovaries consist of the germinal epithelium made up of epithelial cells, over a capsule of connective tissue called the tunica albuginea. Beneath this lies the ovarian cortex, which contains many ovarian follicles surrounded by dense irregular connective tissue containing collagen fibres and fibroblast like cells called stromal cells. Deep to the ovarian cortex is the ovarian medulla. There is no distinct border between the cortex and the medulla, however tissues are more loosely arranged and contains nerves, lymphatic vessels, and blood vessels.

The cortex of the ovaries contain ovarian follicles in various stages of development, mature follicles which are ready to burst, and corpus luteum, the remnants of mature follicles which produces several hormones.

Uterine tubes

The uterine tubes run laterally from the uterus and are around 10 cm long. Each tube has a funnel-shaped portion called the infundibulum, a wider portion called the ampulla making up two thirds of its lateral length, and a narrower part called the isthmus. The infundibulum open out towards the pelvic cavity and the ovaries with fingerlike projections called fimbriae. One of these are attatched to the lateral end of the ovary. The fimbriae sweep the oocyte from the pelvic cavity to the uterine tube.

The uterine tubes are composed of 3 layers: mucosa, muscularis and serosa. The mucosa is made up of a layer of epithelial cells and aerolar connective tissues. The epithelium is composed of ciliated cells and nonciliated cells called peg cells. The ciliated cells brush the ovum towards the uterus and the peg cells secrete fluids with nutrition for the ovum. Surrounding the mucosa is the muscularis made up of an inner layer of circular smooth muscle, and a thiner outer layer of longitudinal smooth muscles. These contracts peristaltically, helping move the oocyte or fertilized ovum towards the uterus. The outside of the uterine tubes are surrounded by a layer of serous membrane.

The Uterus

The uterus is situated between the rectum and the urinary bladder. The uterus is the shape of an inverted pear and is approximately 7.5 cm long 5cm wide and 2.5cm thick in women who have never been pregnant. It is slightly larger in women who have been recently pregnant and smaller when sex hormone levels are low eg. during menopause.

The uterus is subdivided into several parts. The dome shaped portion superior to the uterine tubes is called the fundus, the tapering central portion is called the body, and a narrow portion is called the cervix. Between the cervix and the body is a constricted region called the isthmus. The interior of the body of the uterus is called the uterine cavity and the interior of the cervix is called the cervical canal. The opening between the cervical canal and the uterine cavity is called the internal os (os = mouthlike opening) and the opening between the cervical canal and the vagina is called the external os.

The uterus is held in position by several ligaments. The broad ligaments extend from the peritoneum attatching the uterus to both sides of the pelvic cavity. The paired uterosacral ligaments extends from the peritoneum from either side of the rectum joining the uterus to the sacrum and the cardinal ligaments, inferior to the broad ligament joins the cervix and vagina to the pelvic wall. The round ligaments are connective tissues between the broad ligaments which join beneath the uterine tubes to the labia majora. The uterus usually lies superior and anteriorly over the bladder. This position is called anteflexion. The uterus may occasionally shift to a posterior position, called retroflexion. 

The uterus is made up of 3 layers of tissues. The perimetrium, the myometrium and the endometrium. The perimetrium is a part of the visceral peritoneum (serous membrane of the abdomen) and becomes the broad ligament laterally. It covers the bladder anteriorly and the rectum posteriorly forming the vesicouterine pouch and rectouterine pouch between the organs. The myometrium consists of three layers of smooth muscles which are thickest at the fundus. The first and last layers are longnitudinal or oblique whilst the layer in the centre is circular. These muscle contract during parturition (childbirth) The endometrium is the inner most layer of the uterus and is made up of three components. Lining the lumen of the uterus is an epithelial layer of ciliated cells and secretory cells. Beneath this is the endometrial stroma, made up of areolar connective tissues. Through out the endometrium are endometrial glands which extend from the lumen to almost the myometrium. The endometrium can be devided into 2 layers. The stratum functionalis sloughs off during menstruation whereas the stratum basalis is permenant and grows into the new stratum functionalis after each period.

The uterus receives its nutrients through the uterine arteries which branches from the internal iliac artery. The uterine arteries give off branches called the arcurate arteries which surround the myometrium in circles. Radial arteries branch off from the arcuate arteries and penetrate deeply into the myometrium where it splits again into straight artrioles which supply the stratum basalis and the spiral arterioles which supply the stratum functionalis. Blood drains out via the uterine veins into the internal iliac vein.

Cervical mucus

Secretory cells of the cervix secrete a mucus of water, glycoprotiens, lipids, enzymes, and inorganic salts. This becomes less viscous and more alkaline during ovulation. The mucus supplements the energy needs of sperm and protects tem from phagocytes and may have a role in capacitation during ovulation but physically impede sperm movement at other times.

The vagina

The vagina (sheath) is a fibromuscular canal around 10 cm long. It holds the penis during sexual intercourse and is the outlet for menstrual flow and childbirth. The vagina runs from the exterior of the body to the cervix of the uterus.

The vagina has 3 main layers; the mucosa, the muscularis and the adventitia. The mucosa is continuous with that of the uterus and is made of epithelial cells and areolar connective tissue. The mucosa contains large stores of glycogen which forms acids when decomposed, slowing bacterial growth. The muscularis is made up of an inner longnitudinal layer of smooth muscle and an outer circular layer of smooth muscle. The outermost side of the vagina is called the adventitia, and is made up of areolar connective tissues attatching the vagina to adjacent organs.

The opening to the vagina, the vaginal orifice, is partially covered by a membrane called the hymen. This is usually ruptured following the first sexual intercourse.

The vulva

The vulva refers to the external female genitals. This consists of:

The mons pubis (mons= mountain) refers to adipose tissue anterior to the vaginal and urethral openings, cushioning the pubic symphysis. It is covered in skin and hair.

The labia majora refers to two folds of skin extending posteriorly . They are covered in hair, sebaceous glands and sweat glands, and contain large amounts of adipose tissue.

The labia minora refers to 2 folds of skin medial to the labia majora. This is devoid of hair and fat and have few sweat glands, but many sebaceous glands.

The clitoris is made up of two small erectile bodies. It is located at the anterior junction of the labia minora. The layer of skin covering the clitoris where the labia minora joins is called the prepuce of the clitoris, and the exposed portion is called the glans clitoris.

The region between the labia minora is called the vestibule, This contains the vaginal and urethral orifice, the hymen, and the opening to several glands. Deep to the labia are two long masses of erectile tissue called the bulb of vestibule. This becomes stiff during sexual arousal narrowing the vaginal orifice and placing pressure on the penis.

Mammary Glands

The breasts are found anterior to the pectoralis major and the serratus anterior muscles and are attatched to them by a fascia of connective tissues. The suspensory ligaments of the breast run from the fascia to the skin supporting the breasts. Each breast has a pigmented projection called the nipple where the openings to the lactiferous ducts are. The pigmented area of skin around the nipples is called the areola.

The breasts house the mammary glands. This consists of 15 – 20 lobes separated by adipose tissue, each of which are made up of smaller lobules made up of clusters of milk secreting glands called alveoli. Myoepithelial cells and connective tissue surround the alveoli. The myoepithelial cells contract to propel milk towards the nipples. Milk enters a series of secondary ducts before entering the mammary ducts. These contain sinuses called lactiferous sinuses where milk may be stored before it is expelled.

Milk synthesis is mainly stimulated by the hormone prolactin with contributions from progesterone and estrogen. The ejection of milk is stimulated by oxytocin which is released by the mechanical stimulation of the nipples.