What covers the ovaries?
2. A layer of mesothelium (cuboidal / squamous) on the outside
What are the two parts of the ovary and what is found in them?
No distinct boundary
What is the ovarian stroma?
Connective tissue containing collagen fibers, ground substance, smooth muscle cells, and fibroblast like cells which is found in the outer cortex
What type of oocyte do primordial follicles have?
One oocyte arrested in prophase 1 of Meiosis 1 (diplotene stage). Called primary oocyte. They can stay in this phase for 12-50 years.
What type of cells surround the oocyte in primordial follicles? What surrounds them?
A single layer of squamous cells called follicular cells. They are surrounded by a basal lamina, which is surrounded by the connective tissue of the ovarian cortex.
What are the two types of primary follicles?
What changes occur from primordial to primary follicle?
What is the Zona Pellucida and how does it stain?
The layer forming in the primary follicular stage consisting of four major glycoproteins ZP1-4, secreted by the primary oocyte. It is between granulosa cells and oocyte.
Stains pink / red with H&E, and magenta with PAS (glycoprotein)
What are cortical granules for?
They contain proteases that are released if the oocyte is fertilized by sperm. Cortical reaction is used to block multiple fertilization events
What are theca cells, their two types, and when do they form?
They are connective tissue cells surrounding the basal lamina of the granulosa cells.
Theca interna: well vascularized with endocrine characteristics
Theca externa: less well vascularized, blends in with CT stroma of ovarian cortex
They form in the primary follicular stage but are best seen in secondary follicular
What changes occur from primary follicle to secondary (antral) follicle?
What factors stimulate the growth of the primary follicle?
FSH, growth factors, and calcium
What stops the oocyte from increasing in size during the antral stage?
oocyte maturation inhibitor (OMI) that is secrete by the granulosa cells into the antral fluid
What forms the cumulus mass?
When a mound of granulosa cells becomes eccentrically located in the secondary / antral follicle
What is the corona radiata?
Granulosa cells of the cumulus mass that immediately surround the oocyte and remain with it during ovulation
What fluid fills the antrum?
Liquor folliculi - composed mainly of hyaluronic acid, as well as other hormones and growth factors such as oocyte maturation inhibitor
What is the function and stimulation of the theca interna cells?
Steroid-secreting endocrine cells which have receptors for luteinizing hormone (LH). They synthesize and secrete androgens + some progesterone, which pass through the basal lamina and are uptaken by granulosa cells
What do granulosa cells do under FSH control?
Convert the androgen androstenedione from theca interna cells into estradiol. Estrogen stimulates granulosa cell proliferation, increasing the size of the follicle.
During what stage do granulosa cells start to get LH receptors?
Secondary / antral stage
What characterizes the Graafian follicle stage?
What is released during ovulation?
Secondary oocyte, granulosa cells of corona radiata, and granulosa cells of the cumulus mass.
What happens to the lumen of the corpus luteum, which was occupied by the antrum of the follicle?
It is replaced by a blood clot and then by connective tissue.
What do the theca interna and granulosa cells become in the corpus luteum? How do they appear?
Theca interna: Theca lutein cells - small, less cytoplasm, basophilic
Granulosa: Granulosa lutein cells - large, eosinophilic
The theca cells invade into the granulosa and appear as strands.
What is meant by “luteinization”?
Luteinization = cells become filled with lipid, induced by LH surge. This works because both granulosa cells and theca interna cells now possess LH receptors. Both cell types will now produce mainly progesterone and some estrogen.