CH35 HORMONAL CONTROL OF THE REPRODUCTIVE CYCLE

Hormones

Hormone	Site of secretion	Ovary	Function
Follicle stumulating hormone	Pituitary gland	Ovary	stimulates follicle development in ovary
Luteinising hormone	Pituitary gland	Ovary	Stimulates ovulation
Oestrogen	developing follicle/yellow body	Uterine lining, pituitary gland	stimulates uertine lining to thicken
Progesterone	Yellow body	Uterine lining/Pituitary gland	Maintains thickened uterine lining

Le Mechanisme

Ptuitary gland seretes more FSH
--> FSH stimlulates follicle development
follicle secretes oestrogen --> inhibits FSH and LH
Fall in LH and FSH
Oestrogen +++ --> high lvl --> stimulates secretion of FSH and LH
LH surge --> ovulation occurs
LH: follicle --> yellow body (aka corpus luteum): secretes oestrogen & progesterone
Oestrogen --> thicken uterine lining; Progesterone --> maintains thickness; both inhibit LH and FSH, stimlulates blood vessel development for implantation
If no implantation, low LH levels cause yellow body to degenerate --> low oestrogen and progesterone
uterine lining cannnot maintain thickness and breaks down= menstruation

Fertilization/ implantation

Placenta secretes HCG (human chorioinic gonadotrophin) which prevents degeneration of yellow body --> high levels of oestrogen and progesterone

Several Significant Features

High levels of progesterone/ oestrogen (before ovulation/ after ovulation) inhibits FSH and LH
--> prevents development of more than one follicle to avioid spending energy and resources
--> increase survival chance of foetus as no competition of resources