The Menstual Cycle

Question 0

Fetal period

Answer 0

2nd trimester->mitotic divisions stop, oogenia increase in size-> enter first mitotic division, remain here for many years-> primary oocyte (millions)
1 million at birth, degeneration continues throughout life.
Surviving primary oocyte a acquire a single layer of granulosal cells -> primordial follicles

Question 1

Role of gonadotropins, oestrogen and progesterone in regulating the menstrual cycle.
Embryonic perio

Answer 1

Gonadotropin independent.
4-5 weeks gestation-> migration of stromal cells and primordial germ cells from yolk sac to ovary
5 weeks onwards-> PGC’s undergo mitosis->oogenia, thecal layers (formed by stromal calls) secrete steroid hormones

Question 2

Puberty

Answer 2

Gonadotropin dependent
Follicular development and maturation
Ovarian cycle commences

Question 3

Menstrual cycle 1

Answer 3

Cyclie secretion of FSH
Development of primary follicle
Enlargement of oocyte
Proliferation of granulosal cells (oestradiol)
Formation of zone pellucida between oocyte and cells-> protection and avoidance of polyps perms
cAMP from granulosa cells maintains meiotic onset

Question 4

Menstrual cycle 2

Answer 4

Development of secondary follicle (FSH)
Granulosal cells continue to proliferate
Antral cavities appear, Rich in hyaluronic acid
Stromal cells condense around follicle->atheca, interna, and theca extens

Question 5

Menstrual cycle 3

Answer 5

Graafican follicle development
Fluid filled spaces coalesce->Antrum
Follicle separated from fluid by granulosa cells->cumulus oomphorus
Increased oestrogen secretion-> proliferation of granulosa cells
Granulosa cells express LH receptors

Question 6

Menstrual cycle 4

Answer 6

Pre ovulation follicle
Oocyte completes first stage of meiosis->haploid gamete and small polar body->meiosis stops
Oocyte is freed from follicle wall-> still surrounded by granulosa cells-> corona radiata
Oocyte expelled in to peritoneal cavity
Rupture of follicle

Question 7

Menstrual cycle 5

Answer 7

Corpus luteum
Formed from remaining granulosa cells of theca internus
LH-> lutenization
Granulosa cells-> enlarge and fill with lipid->produce progesterone->supresses GnRH feedback->no new follicle development
Theca cells become smaller-> less estrogen
Central blood clot
If no fertilisation occurs becomes acellular corpus albicans-> progesterone and oestrogen

Question 8

Consequences of pregnancy on the menstrual cycle

Answer 8

HCG from the placenta prevents degeneration of corpus luteum->signals pituitary to secrete LH
corous luteum secretes progesterone->maintains endometrium

Question 9

Layers of uterus wall

Answer 9

External serosa
Peritoneum
Myometrium
Endometrium

Question 10

Endometrial phases 1

Answer 10

Proliferative phase
Functional layer, rich in glands
Basal layer can produce functional layer
Oestrogen stimulates mitotic activity in glands and stroma-> increases thickness

Question 11

Endometrial phase 2

Answer 11

Secretory phase
Glands become saw toothed and secretory under progesterone control
Spiral arteries enlarge

Question 12

Endometrial phase 3

Answer 12

Receptive phase

Epithelial micro villi loose negative charge for 5-7 days after ovulation-> allows implantation

Question 13

Endometrial phase 4

Answer 13

Menstrual phase
Death of corpus luteum->no progesterone and oestrogen
Induction of functional layer of endometrium
Vasoconstriction of spiral arteries->ischemia of functional endometrium
Rupture and shedding of blood in to uterus
Necrotic tissue shed with blood, basal layer remains