Histology of the Female Genital System

The Female Genital System The female genital system consists of: Primary sex organ: two ovaries. Accessory sex organs: two oviducts (Fallopian tubes). a uterus. a vagina. external genitalia. two mammary glands.

THE OVARIES

The Ovaries The ovary is a flattened almond-shaped small body, divided into peripheral cortex and central medulla. The cortex is broad and contains the ovarian follicles separated by the inter-follicular tissue. The medulla consists of highly vascular connective tissue, having elastic fibers, smooth muscle fibers, lymphatics and nerves.

Stroma of The Ovaries Tunica albugenia is the covering connective tissue capsule of the ovary. It is formed of white collagenous connective tissue fibers. Stromal cells: are fusiform cells with oval nuclei similar to fibroblasts. They are present between the ovarian follicles. Reticular connective tissue: present in-between the ovarian follicles.

Parenchyma of The Ovaries The ovarian follicles. In different stages of development and degeneration. The endocrine cells: polygonal in shape, with central rounded nuclei. Their cytoplasm is rich in lipoid granules. In animals, they secrete female hormones, but not in humans. The germinal epithelium: it covers the ovary from outside. It is simple cuboidal in young females and simple squamous in adults.

The Ovarian Follicles They are present mainly in the cortex of the ovary under the tunica albuginea. They are: Primordial follicles. Primary follicles. Secondary follicles. Mature follicles. At birth, the average number of 1ry follicles is 4000, only 400 ova are produced during the reproductive period of the adult female. The remaining follicles degenerate and change to atretic follicles which are converted to white connective tissue bodies.

(1) Primordial Follicles They are derived from the primordial germ cells in the yolk sac and then migrate to the developing ovary. They are formed of central primary oocytes which are surrounded by a single layer of simple squamous cells called follicular cells. The oocyte is a large cell with large eccentric vesicular nucleus with a large nucleolus. Its cytoplasm contains a well-developed Golgi apparatus, RER, mitochondria and lipid droplets.

(2) Primary Follicle The oocyte enlarges and develops Golgi apparatus, ribosomes and mitochondria. It becomes surrounded by a thick highly acidophilic glycoprotein coat, called zona pellucida. The flat follicular cells becomes cuboidal and multiply to give rise several layers (stratified) called granulosa cells. The connective tissue surrounding the follicle condenses and forms two layers; inner highly vascular secretory layer, theca interna and outer fibrous layer, theca externa.

(3) Secondary Follicle The granulosa cells reach 6-12 layers and start to secrete fluid which forms irregular spaces between the granulosa cells. The spaces gradually fuse to form a crescentic space called antrum which contains liquor folliculi. The liquor folliculi contains growth factors, steroid and gonadotrophic hormones. The oocyte is eccentric and is surrounded by a mass of granulosa cells called cumulus oophorus. The oocyte starts its first meiotic division and remains in the prophase until ovulation.

(4) Mature Graafian Follicle The primordial follicle reaches maturity in 10-14 days and occupies the whole thickness of the cortex and bulges out on the free surface of the ovary. The liquor folliculi accumulates between the cells of cumulus oophorus freeing the oocyte from the cells except for one layer called corona radiata cells. The granulosa cells secrete estrogen. The ovum is the largest cell in the body. It has a large, rounded eccentric nucleus

Ovulation It occurs between day 10-14 of the ovarian cycle. It is under influence of LH of pituitary. The Graafian follicle rupture through the stigma due to increase of liquor folliculi. After ovulation, the oocyte with its surrounding corona radiata enters the oviduct, complete its first meiotic division and start the second meiotic division (which is completed after fertilization). The remaining of the mature follicle is transformed into corpus luteum.

Corpus Luteum It is considered as a temporary endocrine organ. Basement membrane between theca interna and granulosa cells dissolves, and capillaries grow in-between granulosa cells. After ovulation, granulosa cells enlarge and accumulate lipid droplets and called granulosa lutein cells. Under influence of LH, the granulosa cell secrete progesterone and estrogen. The same also happens to theca interna cells which are now called theca lutein cells

Fate of Corpus Luteum If pregnancy occurs, it enlarges and continues to function for 3 moths till the placenta is formed and take the gob. If pregnancy does not occur, it degenerates and is transformed into fibrous tissue called corpus albicans.

THE OVIDUCT

The Oviduct It extends from the ovary to the uterus. It is divided into 4 segments: Infundibulum: funnel-shaped opening, having finger-like processes (fimbriae). Ampulla: the widest part, where fertilization usually occurs. Isthmus: narrow part near to uterus. Intramural part: traverses the uterine wall

Histology of the Oviduct Mucosa: highly folded and is formed of Epithelium: simple columnar, partly ciliated (to moved the ovum toward the uterus) and partly non-ciliated (secretory peg cells, nutritive to the ovum). Lamina propria: connective tissue rich in blood vessels. Musculosa: inner circular and outer longitudinal smooth muscle fibers. Serosa: areolar connective tissue covered by simple squamous mesothelium.

THE UTERUS

The Uterus It is a thick-walled pear-shaped organ which has a narrow lumen. It is formed of body and cervix. The body is formed of three layers: Endometrium. Myometrium. Perimetrium.

The Endometrium It is lined by simple columnar epithelium. Its lamina propria contains simple tubular mucous glands lined by columnar epithelium and may reach to the myometrium. It undergoes cyclic changes in response to ovarian hormones. It is divided into superficial layer (stratum functionalis) and deep layer (stratum basalis).

The Myometrium Three layers of smooth muscle fibers and connective tissue. They are not easily distinguished from each other. The middle layer is called stratum vascularis and contains numerous large blood vessels. During pregnancy, the smooth muscle fibers increase in length.

The perimetrium It is formed of areolar connective tissue, blood vessels and covered by simple squamous mesothelium.

Cyclic changes of the endometrium Menstrual stage (from day 1 to day 5). Proliferative phase (from day 6 to day 16). Secretory phase (from day 17 to day 26). Premenstrual stage (from day 27 to day 28).

(1) Menstrual Stage Due to hormonal deficiency specially progesterone. Constriction of coiled arteries for long periods causes ischemia and rupture of capillaries. Glands fragment and uterine fluid, tissue debris and blood are sloughed out and discharged through vagina. Stratum functionalis is lost

(2) Proliferative Stage Occurs during maturation of follicles till ovulation. Under the effect of estrogen secreted by the follicles. It is the stage of regeneration of the stratum functionalis from stratum basalis. Epithelium of basal glands recovers the raw surface. Glands increase in length, become straight and uniform in diameter. Endometrium increases in thickness from 0.5 mm to 2-3 mm.

(3) Secretory Stage Related to the formation of corpus luteum. Under the effect of progesterone and estrogen secreted by the luteal cells. Endometrium becomes hypertrophied and vascular to reaches its full thickness (4-5 mm). Endometrial glands become coiled (cork-screw). The glandular lumen contains secretions and rich in glycogen.

(4) Premenstrual Stage Related to the involution of the corpus luteum and formation of corpus albicans. Spiral arteries undergo periodic constriction leading to stasis in capillaries and periods of ischemia. Glands stop secretion leading to shrinkage of stratum functionalis due to water loss. The thickness of the endometrium decreases. Stratum functionalis appears deeply stained because of the closely packed stromal cells.

The Cervix It consists of: Endometrium: Epithelium: simple columnar mucous-secreting epithelium. Lamina propria: contains branched tubular glands secreting mucous. The cervical endometrium does not change during the menstrual cycle, only the amount and consistency of the mucous chnge. Myometrium: dense connective tissue and few amount of smooth muscle fibers. Adventitia: connective tissue (no peritoneum)

THE VAGINA

The Vagina It consists of: Mucosa: Epithelium: stratified squamous non-keratinized epithelium rich in glycogen. Lamina propria: contains lymphatic nodules but no glands. Musculosa: longitudinal muscle fibers continuous with uterine muscles. Adventitia: dense connective tissue.

MAMMARY GLANDS

Mammary Glands It consists of lobes and lobules, separated by septa formed of dense connective tissue and elastic fibers. Fat tissue runs between lobes and lobules. Non-lactating gland (inactive): the gland parenchyma is formed of little amount of lactiferous ducts only, with no alveoli.

Lactating Mammary Glands Stroma: connective tissue septa and adipose tissue are reduced. Parenchyma: extensive system of secretory alveoli budding from the ducts. The alveoli are lined with simple cuboidal cells with basal myoepithelial cells. The intralobar ducts are lined with simple cuboidal epithelium. The main ducts are lined with stratified squamous epithelium. Mammary gland is an apocrine gland. Prolactin stimulate secretion of milk. Oxytocin stimulate ejection of milk.