First Week Of Development: Ovulation To Implantation

Front 1

How does the sexual cycle of female is controlled by hormone?

Back 1

The sexual cycles are controlled by the hypothalamus. Gonadotrophin releasing hormone(GnRH), produced by the hypothalamus acts on cells of the anterior lobe ( adenohypophysis) of the pituitury gland, which in turn secrete gonadotrophins. These hormones, follicle stimulating hormone( FSH) and luteinizing hormone(LH) stimulate and control cyclic changes in ovary.

Front 2

Each months, how many follicles are grow and matured?

Back 2

At the beginning of each ovarian cycle, 15-20 primary stage (preantral) follicles are stimulated to grow under the influence of FSH.

Front 3

What is the significant of FSH in devolopiing follicles?

Back 3

FSH is not necessary to promote development of primordial follicles to the primary follicle stage, but without it, these primary follicles die and become atretic.

Front 4

What happen when a follicle dies?

Back 4

When a follicle becomes atretic, the the oocyte and surrounding follicular cells degenerate and are replaced by connective tissue, forming a Corpus atreticum .

Front 5

What does FSH do to the growing follicle?

Back 5

FSH stimulates maturation of follicular(granulosa) cells surrounding the oocyte.

Front 6

What what mediate the proliferation of granulosa cells?

Back 6

Growth diffeentiation factor 9, a member of the transforming growth factor beta(TGF-beta) family.

Front 7

How the estrogen production happens?

Back 7

Theca interna and granulosa cells produce estrogens. Theca interna cells produce androstenedione and testosterone, and granular cellsconvert these hormones to estrone and 17 beta-estradiol.

Front 8

What are the results of estrogen production?

Back 8

• The uterine endometrium enters the follicular or proliferative phase.

• Thinning of the cervical mucus occurs to alllow passage of sperm.

• The anterior lobe of the pituitary gland is stimulated to secrete LH.

Front 9

What are the effects of LH surge?

Back 9

• Elevatesconcentrations of maturation promoting factor, causing oocytes to complete meiosis Iand initiate meiosis II

• Stimulates production of progesterone by follicular stromal cells (luteinization)

• Causess follicular rupture and ovulation.

Front 10

What happen immediately before ovulation?

Back 10

In the days immediately preceding ovulation, under the influence of FSH and LH, the vesicular follicle grows rapidly to a diameter of 25mm to become a mature vesicular (graafian) follicle.

Coincident with final development of the vesicular follicle, there is an abrupt increase in LH that cause the primary oocyte to complete meiosis I amd the follicle to enter the preovulatory mature vesicular stage.

Meiosis II is also initiated, but the oocyte is atrested in metaphase approximately 3 hours before ovulation.

In the meantime, the surface of the ovary begins to bulge locally, and at the apex, an avascular spot, the stigma appears.

Front 11

What happen when LH conc. increases?

Back 11

The high conc. of LH increases collagenase activity, resulting in digestion of collagen fibres surrounding the follicle.

Prostaglandin levels also increases in response LH surge and cause local muscular contractions in the ovarian wall.

Those contractions extrude the oocyte, which together with its surrounding granulosa cells from the region of the cumulus oophorus breaks free(ovulation) and floats out of the ovary.

Front 12

How corona radiata forms?

Back 12

Some of the cumulus oophorus cells rearrange themselves around the zona pellucida to form the corona radiata.

Front 13

How corpus luteum is formed?

Back 13

After ovulation, granulosa cells remainaing in the wall of the ruptured follicle, together with cells from the theca interna are vascularised by surrounding vessels. Under the influence of LH, these cells develop a yellowish pigment and change into lutein cells , which form the corpus luteum.

Front 14

What does corpus luteum secrete? And what are their functions?

Back 14

Corpus luteum secrete estrogens and progesterone. Progesteron together with some estrogen causes the uterine mucosa to enter the progestational or secretory stage in preparation for implantation of the embryo.

Front 15

Hiw is the oocyte transported?

Back 15

Shortly before ovulation, fimbriae