L24 - hormones and reproduction Flashcards
where are seminiferous tubules located
testes
what occurs in seminiferous tubules
sperm production
what is found in spaces between seminiferous tubules
blood vessels
nerve tracks
leydig cells
what stimulates legdig cells
LH
what cells are found in seminiferous tubules
sertoli cells (large) spermatogonium (smaller in clusters)
function of FSH
stimulates gamete production (sperm/egg)
function of LH
stimulates production of steroid hormones
name the sex steroid hormones
androgens
oestrogens
progesterones
how do the steroid hormones generally bring about their effect
cross membrane and bind to intracellular receptors - alter gene transcription
function of androgens
male reproductive characteristics
what is the main androgen
testosterone
where are androgens synthesised and released from
testes and adrenal gland
function of oestrogens
female reproductive hormones
main oestrogen
oestradiol
where are oestrogens synthesised and released
mainly synthesised from androgens and released rom ovaries
function of progestogens main progestogen
involved in menstrual cycle and pregnancy
progesterone
explain HPG axis (female)
- hypothalamus releases GGnRH to anterior pituitary
- anterior pituitary releases FSH and LH
- FSH and LH act on gonads to produce gametes and steroid hormones
- steroid hormones have -ve feedback on AP and H
explain male HPG axis
- hypothalamus GnRH
- anterior pituitary LH, FSH
- LH stimulates leydig cells to produce and release testosterone
- FSH & testosterone stimulate spermatogenesis
- FSH regulates spermatogenesis by acting on sertoli cells
in what cells does spermatogenesis occur
spermatogonial cells
function of sertoli cells
support, nutrition, protection, regulation
name the 3 phases of the menstrual cycle and the times they occur
- follicular phase (day 1-10)
- ovulatory phase (day 11-14)
- luteal phase (12-28)
what initiates and regulates the menstrual cycle
changes in levels of LH, FSH, oestradiol, progesterone
describe follicular phase
- FSH stimulates follicle growth
2. theca and granulosa cells (that surround follicle) stimulated by LH to release oestradiol
how many follicles make it do day 10 and why
1
competition for FSH
describe ovulatory phase
- when oestradiol levels high enough it stimulates LH causing LH surge
- LH surge triggers ovulation
what does LH surge trigger
ovulation
explain relationship between oestradiol and LH
normally oestradiol inhibits LH (-ve feedback) but when levels are high enough it causes LH surge
describe luteal phase
- oocyte released - remaining follicle becomes corpus luteum
- corpus luteum releases oestradiol and progesterone to prepare for possible pregnancy
- no pregnancy = corpus luteum degenerates
what does corpus luteum release and why
oestradiol and progesterone to prepare for possible pregnancy
what happens to corpus luteum if no pregnancy
degenerates
where is oestradiol released from and how
LH stimulates theca and granulosa cells (that surround follicle) to release oestradiol
what stimulates spermatogenesis
FSH and testosterone
describe ovaries appearance
follicles surrounded by connective tissue and stroma
what is in the centre of an ovary follicle
oocyte
