2.2 Hormonal Control Of Reproduction
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In males, hypothalamus secrets a hormone which causes the pituitary gland to produce what two hormones?
FSH- follicle stimulating hormone ICSH- interstitial cell stimulating hormone
In women, hypothalamus secrets a hormone which causes the pituitary gland to produce what two hormones?
FSH- follicle stimulating hormone LH - lutenising hormone
FSH in males
Promotes sperm production in seminiferous tubules
ICSH in males
Stimulates interstitial cells to produce testosterone
FSH in women
Stimulates development & maturation of each follicle Stimulates ovary to secrete oestrogen
LH in women
Triggers ovulation & brings about development of corpus luteum to secrete progesterone
What does the male sex hormone testosterone do?
Stimulates sperm production and activates seminal vesicles and prostate gland to produce secretions
What is negative feedback control in men?
Testosterone conc builds up & reaches a level which inhibits secretion of FSH & ICSH Then leads to a decrease in testosterone conc & pituitary gland releases FSH & ICSH again
What does Oestrogen stimulate?
Stimulates proliferation of endometrium to prepare uterus for embryo
Highest conc of oestrogen is just before ovulation what does it stimulate then?
Stimulates cervix to secrete a thinner and watery mucus that can be penetrated by sperm Also LH by pituitary gland
What does progesterone do?
Promotes further development & vascularisation of endometrium to form a spongy layer made of blood vessels to prepare for embryo Also inhibits FSH & LH by pituitary gland
How long does a mensural cycle last and what are the stages?
Lasts 28 days Follicular phase (1-14) Luteal phase (14-28)
What does pituitary gland do during follicular phase?
Releases FSH which brings about development of follicle & production of oestrogen by ovarian tissue
What happens to concentration of oestrogen in follicular phase?
Builds up and brings about repair & proliferation of endometrium Also triggers surge in LH & FSH around day 14 which causes ovulation
How long does egg move down oviduct before fertilisation can occur?
3-4 days
During Luteal phase corpus luteum secretes progesterone & oestrogen which inhibits
Production of LH & FSH & If fertilisation doesn’t occur lack of LH degenerates corpus luteum which leads to rapid drop in progesterone & oestrogen & menstruation begins
What hormone does embryo secrete if fertilisation occurs?
HCG- human chronic gonadotropin which has same effect as LH
What does HCG do?
Maintains corpus luteum & secretes progesterone & also prevents menstration.
After 6 weeks placenta takes over to secrete
Progesterone