female reproductive system

Female reproductive system

The female reproductive system has six major functions:
Production of female gametes, the ova, by the process of oogenesis. Reception of male gametes, the spermatozoa. Provision of a suitable environment for the fertilisation of ova by spermatozoa. Provision of an environment for the development of the fetus. Expulsion of the developed fetus to the external environment. Nutrition of the newborn.

Ovary

The superficial cortex is more fibrous than the deep cortex and is often called the tunica albuginea. On the surface of the ovary is an epithelial covering, misleadingly called germinal epithelium which is a continuation of the peritoneum. central zone of the ovarian stroma, the medulla M, is highly vascular and contains hilus cells, which are morphologically very similar to Leydig cells of the testis.

During early fetal development, primordial germ cells called oogonia migrate into the ovarian cortex where they multiply by mitosis. By the fourth and fifth months of human fetal development, some oogonia enlarge and assume the potential for development into mature gametes. At this stage they are called primary oocytes and commence the first stage of meiotic division, by the seventh month of fetal development, a single layer of flattened follicular cells surrounds the primary oocytes to form primordial follicles. approximately 500 000 in the human ovary at birth. This encapsulation arrests the first meiotic division and no further development of primordial follicles then occurs until after the female reaches sexual maturity. process of meiotic division is only completed during follicular maturation leading up to ovulation and fertilization. Thus all the female germ cells are present at birth but the process of meiotic division is only completed some 15-50 years later.


During each ovarian cycle, a cohort of up to 20 primordial follicles is activated to begin the maturation process; nevertheless, usually only one follicle reaches full maturity and undergoes ovulation while the remainder regress before this point. Follicular maturation involves changes in the oocyte, the follicular cells and the surrounding stromal tissue. Follicular maturation is stimulated by FSH (follicle stimulating hormone) secreted by the anterior pituitary gland.

primordial follicles that are usually located near the tunica albuginea. These follicles will be surrounded by flattened follicular cells. The primary oocyte within the follicle has pale, granular cytoplasm, a pale, round nucleus, and a dark nucleolus. Primary follicles result from growth of primordial follicles. They can be subdivided into unilaminar primary follicles and multilaminar primary follicles. The unilaminar primary follicle has entered the initial stage of growth due to stimulation by FSH. It resembles a primordial follicle except that it is surrounded by a layer of cuboidal to columnar granulosa cells. The multilaminar primary follicle is surrounded by two or more layers of granulosa cells, which lack an antrum.

A distinct zona pellucida can be seen in multilaminar follicles. It is a gel-like membrane, rich in glycoprotein, interposed between the oocyte and the granulosa cell. Further growth of a multilaminar follicle leads to the formation of a secondary follicle, which is characterized by an antrum. The antrum is a space among the follicular cells, which appears when follicles reach about 0.2 mm in diameter. The antrum is filled in life with a fluid, the liquor folliculi, and gradually increases in size by the accumulation of fluid.


Tertiary or Graafian follicle a. Has a well developed antrum filled with a fluid called liquor folliculi (or follicular liquor). b. Oocyte located within a hillock of multiple layers of follicle cells that projects into the antral cavity - called the cumulus oophorus. c. The follicle cells directly adjacent to oocyte form the corona radiata that will remain associated with oocyte after ovulation.

All types of follicles may undergo atresia or degeneration. Many primordial follicles undergo atresia before birth. Of those which remain, many degenerate before puberty and others degenerate throughout the reproductive years without entering the growth period. several follicles that begin growth each month, only one, as a rule, is destined for maturity and ovulation. The others undergo atresia. When follicles become atretic, the oocyte is the first structure of the follicle to show signs of dying. Its nucleus becomes pyknotic and its cytoplasm shrinks and then breaks. The zona pellucida of multilaminar follicles thickens and becomes folded. Following death of the oocyte, similar destructive changes occur in the follicular cells. These will be most obvious in secondary follicles, which have more follicular cells. The glassy membrane thickens; the granulosa cells separate and degenerate; the thecal cells accumulate lipid and degenerate. The zona pellucida and thecal cells are the most persistent parts. The final product of an atretic secondary follicle, like that of a degenerating corpus luteum, is a corpus albicans.


The most notable feature of this human ovary is the large corpus luteum. This is an endocrine structure formed from a ruptured follicle, well-vascularized, folded wall and its central lumen, which contains loose connective tissue. Granulosa lutein cells constitute the bulk of the wall. These large cells secrete progesterone and represent cells of the granulosa membrane, which have undergone hypertrophy. The small theca lutein cells can be seen at the periphery of the corpus and in the connective tissue of the folds. They are the estrogen secreting cells derived from the theca interna of the follicles. In addition, there is a large, probably cystic, follicular cavity in the cortex.

* Follicle Development

Primordial follicle: one layer of squamous-like follicle cells surrounds the oocyte Primary follicle: two or more layers of cuboidal granulosa cells enclose the oocyte Secondary follicle: has a fluid-filled space between granulosa cells that coalesces to form a central antrum Graafian follicle: secondary follicle at its most mature stage that bulges from the surface of the ovary Corpus luteum : ruptured follicle after ovulation

* Ovary Histology

Zona pellucida

Granulosa cells

Thecal cells
Nucleus
Primordial follicle
Primary Follicle

* Secondary Follicle

Fluid-filled antrum

* Graafian Follicle

Fluid filled antrum
Granulosa cells

Corona radiata

Stalk
Zona pellucida


Oocyte and follicular cells shed into abdominal cavity then Empty follicle forms corpus luteum which produces progesterone Corpus luteum degenerates and becomes corpus albicans GnRH increases under low estrogen and progesterone levels
Ovulation

oviduct is about 10 cm long. One end opens into the uterine cavity, the other into the peritoneal cavity adjacent to the ovary. The uterine tube is divided into four regions. Each tube begins with the fimbriated, funnel-like opening, the infundibulum. The next segment is the dilated ampulla with its alternating, branching folds and grooves; thereafter, first in the isthmus and then to a larger extent in the intrauterine segment, the tube becomes reduced in diameter and its lumenal mucosa far less folded. The wall of the oviduct consists of a mucosa, muscularis, and external serosa. The mucosa has deep thin folds in the infundibular region. The epithelium is simple columnar. The height of the epithelium is highest in the ampulla and is influenced by hormones, being somewhat higher just before ovulation. There are two types of columnar epithelial cells found in the oviduct, ciliated and nonciliated (aka: peg) cells. The latter are recognized because their nuclei are near the lumen and their cytoplasm (and sometimes nuclei) bulge into the oviduct lumen, they are probably secretory cells . .

Peg cells are probably secretory cells . The lamina propria consists of loose connective tissue and is rich in blood vessels. The lamina propria lacks glands. The smooth muscle in the muscularis is loosely arranged into inner circular and outer longitudinal layers, which are separated by a connective tissue layer. The outer longitudinal layer is best defined in the isthmus becoming less distinct as you approach the fimbriae. It may be unrecognizable in the infundibulum. The serosa or outermost layer of loose connective tissue contains blood vessels, lymphatics, and nerves. The serosa is lined by simple squamous layer of mesothelial cells. The oviduct in isthmus shows the overall reduction in folding of the mucosa and somewhat thicker appearance of the lamina propria. Also the muscularis is thicker and well differentiated into longitudinal and circular layers.


* Fallopian Tube Histology
Cilia sweep egg/zygote toward the uterus

UTERUS

The human uterus can be subdivided into the fundus, corpus (body), and cervix. Functionally, as well as structurally, the fundus and corpus are similar; the cervix differs both structurally and functionally. The layers of the uterus are given special names: the mucosa is called endometrium; the muscularis is the myometrium; the serosa is the perimetrium. During the reproductive years the endometrium in the corpus and fundus undergoes cyclical changes about every 28 days. This menstrual cycle can be divided into four phases: menstrual, proliferative, secretory, and premenstrual.

* Uterine Histology

Endometrium Simple columnar epithelium Stroma of connective tissue and endometrial glands Stratum functionalis: Shed during menstruation Stratum basalis: Replaces stratum functionalis each month Myometrium 3 layers of smooth muscle Perimetrium Visceral peritoneum

* Uterine Histology

* Endometrium
Simple columnar epithelium
Endometrial glands

Endometrium

Proliferative phase: glands and blood vessels scattered throughout the functional zone with little or no branching. New glands form and endometrium thickens. Secretory phase: glands are enlarged and have branches. Preparing the endometrium for implantation If no implantation then endometrium breaks down and menstruation begins.


Early secretory phase. The glands are more tortuous and the spiral arteries extend almost to the epithelial layer. Look closely at the glandular epithelial cells. Many cells will have basally located clear areas. fewer mitotic figures in the glandular epithelium The stroma and bases of the glands in this region undergo little change during the menstrual cycle. They are maintained during menstruation and regenerate another stratum functionalis after menstruation.

Later secretory phase. The appearance is similar except that the endometrium is thicker and the glandular lumen is larger and sometimes contains secretory material. Many cells will have apically located clear areas.

Menstrual phase. The uterus undergoing menstruation. Compare the stratum basalis, which is relatively unaffected, with the stratum functionalis that is being sloughed off the absence of an epithelial lining.

uterine cervix 

The human uterine cervix has a strikingly different appearance to that of the corpus and fundus. The cervical stroma to that of the endometrium in the body of the uterus. The wall differs from the rest of the uterus in that it is mainly composed of dense collagenous and elastic fibers. Only about 15% of the wall is smooth muscle the cervical epithelium showed abrupt transition from simple columnar epithelium (the lining of the cervical canal) to a stratified squamous epithelium, like that found in the vagina. The branched tubular glands secrete mucous. The mouths of the glands sometimes become plugged and the glands expand into cyst-like formations called Nabothian follicles.

Vagina

The vagina extends from the cervix to the vestibule. It has three layers, mucosa, muscularis, and adventitia. The mucosa is lined by non-cornified stratified squamous epithelium. Pale vacuoles in the epithelial cells indicate areas where glycogen was stored. Complex papillae extend to the epithelium from the lamina propria but glands are not present. The lamina propria is rich in elastic connective tissue. The mucosa is highly vascular,. There is also no muscularis mucosa.

The labia majorum. This gradual blends into a keratinized stratified squamous epidermis without hair follicles over the labia minora. The stratum corneum is absent on the inner aspect of the labia minora near the vestibule. The lining of the vestibule is continuous with that of the vagina.

glands

Lesser Vestibular (Paraurethral, Skene's) Male Homolog = prostate located on the upper wall of the vagina, around the lower end of the urethra. They drain into the urethra and near the urethral opening Function - mucus production

* Bartholin’s Glands Male Homolog = bulbourethral glands located slightly below and to the left and right of the opening of the vagina. They secrete fluid that helps lubricate the vagina. Sometimes the ducts of these glands become obstructed. Fluid backs up into the gland and causes swelling (Bartholin's cyst)


Mammary Glands [ breasts]
Present in both sexes - normally only functional in females Developmentally they are derived from sweat glands Contained within a rounded skin-covered breast anterior to the pectoral muscles of the thorax Slightly below center of each breast is a ring of pigmented skin, the areola - this surrounds a central protruding nipple Internally - they consist of 15 to 25 lobes that radiate around and open at the nipple Each lobe is composed of smaller lobules- these contain alveoli that produce milk when a women is lactating non-pregnant women - glandular structure is undeveloped - hence breast size is largely due to the amount of fat deposits

* Breast