OVARY

Location: it is attached to the posterior surface of the broad ligament by a peritoneal fold in the pelvis.

Function:

• Production of gametes (gametogenesis, oogenesis).
• Production of steroids (steroidogenesis) that play the important role in the menstrual cycle.

Anatomic features

• The surface is covered by simple cuboidal or squamous epithelium germinal epithelium. Under it the dense connective tissue tunica albuginea lies.
• Cortex, the peripheral portion, contains ovarian follicles embedded in richly cellular connective tissue with scattered smooth muscle fibers.

• Medulla, central portion, contains loose connective tissue with blood vessels, lymphatic vessels and nerves.

PRIMORDIAL FOLLICLE

Location: just beneath the tunica albuginea.

• Oocyte (about 30 mkm in diameter) arrested in its development at the diplotene stage of meiotic prophase.
• Follicular cells, a single layer of squamous cells those outer surface is bounded by the basal lamina.

PRIMARY FOLLICLE

• Oocyte (about 50 - 80 mkm in diameter) is surrounded by zona pellucida, homogeneous layer rich in glucosaminoglycans.
• Membrana granulosa, stratified epithelium of cuboidal cells those outmost layer lies on basal lamina.
• Theca interna, the inner, highly vascularized layer of cuboidal steroid-secreting cells, fibroblasts, and collagen fibers.

• Theca externa, the outer layer, loose connective tissue with smooth muscle cells.

SECONDARY (ANTRAL) FOLLICLE AND GRAAFIAN FOLLICLE

• Oocyte (about 125 mkm in diameter) with irregular microvilli. It undergoes first meiotic division. One daughter cell receives the majority of the cytoplasm and becomes the secondary oocyte (about 150 mkm in diameter). It begins the second meiotic division and is arrested at metaphase. The other daughter cell receives a minimal amount of the cytoplasm and becomes first polar body.
• Granulesa cells that immediately surround the oocyte and remain with it at ovulation are referred to as the corona radiata. Thickened mound associated with the oocyte is called the cumulus oophorus.
• A large antrum filled by liquor folliculi, hyaluronic acid-rich fluid.

• Theca interna, the inner, highly vascularized layer of cuboidal steroid-secreting cells with lipid droplets, fibroblasts, and collagen fibers.

• Theca externa, the outer layer, loose connective tissue with smooth muscle cells.

CORPUS LUTEUM (LUTEAL GLAND)

Origin: the granulosa and thecal cells of collapsed follicle after ovulation undergo reorganization. At first bleeding from the capillaries of theca interna leads to the formation of the corpus hemorrhagicum with the central clot. Blood and lymphatic vessels from the theca interna rapidly grow into granulosa layer.

Composition:

• Granulosa lutein cells, very large, centrally located cells derived from the granulosa cells.
• Theca lutein cells, small peripherally located cells derived from the cells of the theca interna layer.
• Corpus albicans, a white scar, is the degenerating and involuting form of corpus luteum with large amounts of intercellular hyaline after pregnancy or menstruation. It disappears over a period of several months.

Function:

• corpus luteum of menstruation: secretion of progesterone and estrogenes, that stimulate the growth of endometrium for 14 days.
• corpus luteum of pregnancy: a high level of progesterone blocks the development of the ovarian follicles for 8 weeks.

ATRESIA

Origin: most of the follicles on any stage of their maturation undergo degeneration and disappear.

Stages of degeneration of large follicles:

• Cessation of mitosis and expression of hydrolytic enzymes within the granulosa cells
• Invasion of the granulosa layer by neutrophils, macrophages and strands of vascularized connective tissue
• Sloughing of the granulosa cells into the antrum of the follicle
• Hypertrophy of the theca interna cells
• Invasion of connective tissue into the cavity of the follicle.

INTERSTITIAL GLAND

Origin: theca interna of atretic follicle.

Composition: the strains of luteal cells scattered in the stroma.

Function: secretion of estrogens that influence the growth and development of the secondary sex organs.

HILAR CELLS

Location: in connective tissue stroma near blood vessels and nerves.

Function: epithelioid androgen, steroid-secreting cells.