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endocrinology > The gonads > Flashcards

The gonads Flashcards

1
Q

What do the gonads develop as

A

testes and ovaries

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2
Q

what determines the sex

A

SRY gene on y chromosome makes male characteristics - no SRY gene=ovary develop

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3
Q

in males what cells are the gonads made of and what do they develop into

A

primordial germ cell - spermatogonia
supporting cells - sertoli cells
steroidogenic cells - leydig cells

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4
Q

what are the functions of the gonads

A

gametogenesis - produce gametes - pass on genes

production of steroid hormones - steroidogenesis - steroids important at all aspects of reproduction

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5
Q

male and female gametogenesis

A

spermatogenesis - mature spermatozoa

oogenesis - production of ripe ova

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6
Q

male and female steroidogenesis

A

androgens, small amount oestrogen and progesterone

oestrogen and progesterone, small amount of androgens

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7
Q

describe the activation of sperm cells

A

sperm derivied from stem cells
early in embryo cells proliferate - 6-7million
spermatogonia stay at this level through life
go into quiescence in childhood
spermatogenesis begins at puberty

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8
Q

describe activation of oogonia

A

gametogenesis early in embryo 6-7million
atresia
maximum level 24wks of pregnancy - no more cells produced
2million at birth
400000 puberty
at menopause ovary is depleted

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9
Q

describe the process of spermatogeneis

A

diploid germ cell - multiply and differentiate
spermatogonia - mitotic division at puberty with GnRH, gonadotrophins and testosterone release
(some remain spermatogonia)
diploid primary spermatocytes – meiotic division
secondary spermatocytes – second meiotic division
sermatids
spermatozoa

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10
Q

summarise the production of sperm

A

gametogenesis begins at puberty
pool of spermatogonia remain constantly available for future cycles
produce 200 million sperm daily

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11
Q

describe oogenesis

A

diploid oogenia – mitotic division early in embryogenesis
primary oocytes - have layer around cell, primordial follicle - remain in meiotic arrest in prophase 1 until menstruation
secondary oocytes + polar body – second meiotic division – fertilisation
ovum + polar body

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12
Q

how is a polar body formed

A

one daughter egg cell keep all resources

other is just membrane and chromosome so degrades

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13
Q

summarise the production of female gametes

A

limited number of oogenia

promordial follicles - atrasia

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14
Q

describe the testes

A

coiled seminiferous tubules - - spermatogenesis takes place
move in collecting duct to Rete testes
drained into vas efferentia
through very coiled epididymis, stored there - gain nutrints to mature and develop motility
through vas deferens (surrounded by smooth muscle) to urethra to be expelled

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15
Q

describe seminiferous tissue

A

under connective tissue
spermatogonia along basement membrane
sertoli cells connected at a tight junction - form a blood testes barrier - large molecues can’t enter
spermatogonia enter sertoli cell - network of cytoplasm where they can mature - released into tubule
leydig cells - enzymes for steroidogenesis

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16
Q

describe sertoli cells

A

form seminiferous tubules
synthesis FSH and androgen receptors
produce inhibin, and androgen binding protein as a response to FSH
associated with developing spermatocytes

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17
Q

describe leydig cells

A

lie outside seminiferous tubule
synthesis LH receptor
principle source of testicular androgens - mainly testosterone

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18
Q

connection between sertoli and leydig cells

A

without high conc of testosterone in leydig cells spermatogenesis won’t take place

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19
Q

describe the ovaries

A

follicles contain oocyte and at least 1 layer of cells
there are follicules undergoing atresia
graafian follicle - max size - ready for ovulation
granulosa and thecal cells surround ovum
remnants of last corpus luteum
follicular fluid can be large

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20
Q

steroidogenesis in gonads

A

make progesterones C21
androgens C19
Oestrogens C18

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21
Q

process to make dihydrotestosterone

A 
cholesterol 
pregnenolone 
progesterone 
17-OH progesterone 
androstenedione 
testosterone 
dihdrotestosterone
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22
Q

process to make oestrone

A 
cholesterol 
pregnenolone 
progesterone 
17-OH progesterone 
androstenedione 
oestone
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23
Q

process to make 17B oestradiol

A 
cholesterol 
pregnenolone 
progesterone 
17-OH progesterone 
androstenedione 
testosterone 
17B-oestrodiol
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24
Q

process to make aldosterone

A 
cholesterol 
pregnenolone 
progesterone 
deoxycorticosterone 
corticosterone 
aldosterone
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25
Q

process to make cortisol

A 
cholesterol 
pregnenolone 
progesterone 
17-OH progesterone  
11-deoxycortisol 
cortisol
26
Q

summarise the menstrual cycle

A

28 days
begin on first day of menstruation
ovulation - important reproductive event

27
Q

what does the menstrual cycle consist of

A

ovarian cycle

endometrial cycle

28
Q

how are ovarian and endometrial cycle related

A

follicular phase make 17B-oestrodiol - stimulate proliferative phase in endometrial cycle - lining thicker, add oestrogen and progesterone receptor - stimulate for later stimulation from progsterone
luteal phase in ovarian cycle - make progesterone - reduce proliferation and make oestrogen, increase secretory activity of endometrium - suitable for implantation

29
Q

describe the ovarian cycle

A

pre-antral follicle (gonadotrophin independant)
FSH to early antral follicle
(antrum is fluid filled sac) bigger and produce oestrogen
late antral follicle
graafian follicule - mature follicle
corpus luteum (granulosa cell proliferate, invaded by BV can make oestrogen and progesterone for 13-14 days

30
Q

describe hormone production during the ovarian cycle

A

FSH activate aromatase in granulosa cells (only cell with FSH receptor)
thecal cells have LH receptor
androgen diffuse into granulosa cells
synthesis of oestrogen
process same in corpus luteum
Thecal cells have an LH1 receptor - stimulate steroidogenesis

31
Q

describe the endometrial cycle

A

proliferative phase:
dominant oestrogen thin endometrium thickens, glands grow straight, enlarge coil to survface of endometrium have increased blood supply

secretory phase: progesterone dominant and oestrogen. endometrium becomes secretory later is necrotic and sheds. glands - secrete glycogen and mucopolysaccharides, bv relax mucosa engorged with blood.
blastocyst arrive in uterus - ideal for egg arrival

32
Q

what happens to uterus if no fertilisation

A

oestrogen and progesterone decline
BV constrict - ischemia - necrotic
endometrium stimulate prostoglandins - stimulate underlying myometrium to contract - help shed tissue

33
Q

what is testosterone converted to and where

A

Di-hydrotestosterone potent in prostate, testes (seminiferous tubules) seminal vesicles, skin, brain and adenohypophysis, gives male phenotype, oil production and baldness this is reduction.

17B-oestradiol in adrenals, testes (Sertoli cells) liver, skin, brain. aromatisation - fats, in obesity causes moobs

34
Q

describe the transport of testosterone

A

in blood 60% bound to sex hormone binding globulin (SHBG)
38% to albumin
only 2% bioactive
in seminiferous fluid bound to ABG

35
Q

action of androgen in foetus

A

needed to make male genitalia and descend from the abdomen

mother’s HCG stimulate production of testosterone in utero testosterone needed, with other hormones for foetal growth

36
Q

action of androgens in adults

A

spermatogenesis takes 4 months? maturation requires high testosterone growth and development male genitalia and secondary sex characteristics
muscle and bone growth - lack=osteoporosis
male sex behaviour
pubertal growth spurt
some androgenic effects mediated by conversion to oestrogen in the brain

37
Q

what is oestrogen

A

any substance (natural/synthetic) that induces mitosis in endometrium

38
Q

main oestrogen

A

17B-oestrodiol

39
Q

reproductive action of oestrogen

A 
stimulate proliferation of endometrium 
trigger LH surge in ovulation 
vagina secretions 
in breast stimulate growth of ductile system 
decreases sebaceous gland secretion
40
Q

non-reproductive effects of oestrogen

A

-ve and +ve feedback for GnRH
stimulates osteoblasts - so don’t get osteoporosis
metabolism of lipid - female less chance of CVD
sexual arousal
fluctuates water in menstrual cycle

41
Q

progesterone definition

A

any substance inducing secretory change in endometrium

42
Q

main progesterone

A

progesterone

43
Q

main effect of progesterone

A

stimulates secretory activity in endometrium and cervix so fertilised egg can implant

44
Q

what makes progesterone

A

corpus luteum

45
Q

lesser effects of progesterone

A

increase body temp - see if ovulating
growth of alveolar system in breast - long progesterone to prime breast
competitive inhibition of aldosterone
-ve feedback on hypothalamic GnRH

46
Q

describe the hypothalamo-pituitary-testicular axis

A

Hypothalamic pulse generator
GnRH released from hypothalamus in fluctuation every 1 1/2 to 2 hours
stimulate coincident pulses of FSH and LH release
LH stimulates hormones (androgen production) - Leydig cells - testosterone
FSH stimulates Sertoli cells (spermatogenesis) - inhibin
inhibin and testosterone inhibit hypothalamus and anterior pituitary gland

47
Q

describe the hypothalamo-pituitary ovarian axis

A

pulses of GnRH released every 1 1/2 - 2 hours
stimulate LH and FSH
ovary make oestrogen and progesterone
-Ve feedback against GnRH and LH and FSH

48
Q

what is GnRH

A

gonadotrophin releasing hormone

49
Q

how long is the early follicular phase

A

1st 5 days after day 1 of bleeding

50
Q

describe the early follicular phase

A 
LH and FSH cause follicles to develop 
5-10 eggs enlarge 
Graafian follicles develop 
grow under FSH regulation 
make oestradiol and little progesterone 
little oestrodiol so high LH and FSH - cause follicles to grow
51
Q

describe the early mid follicular phase

A

oestradiol increases - follicular cells grow
largest follicle grow and make more oestrogen
-e feedback loop to LH and FSH
get autocrine +ve feedback loop - more oestrogen=more granulosa cells

52
Q

mid-follicular phase

A

now LH and FSH turn off because of rising oestradiol (E2)

kills all follicles except Graafian follicle - autonomous - make own oestrogen

53
Q

describe the late follicular phase

A

Extremely high E2 causes +ve feedback on GnRH and LH secretion - pituitary activated by oestrogen - causes LH surge when E2 has reached threshold (10x higher than normal)
2 population of GnRH neurons +ve feedback require high level oestrogen to kick in
cause follicle to open and egg release down follicular tube

54
Q

describe the luteal phase

A

progesterone prepares the endometrium for implantation
corpus luteum make progesterone in 2nd half of cycle/pregnancy - convert endometrium to secretory lining
progesterone, oestradiol and inhibin -ve feedback on LH, FSH
luteolysis, corpus luteal involutes - menstruation

55
Q

what is amenorrhoea

A

absence of menstrual cells
primary - if never had a period, born without GnRH
secondary - women had periods and then stop

56
Q

what is oligomenorrhoea

A

infrequent cycles, less severe than amenorrhoea,

57
Q

definition of infertility

A

couple cannot get pregnant after 12 months of unprotected sex

58
Q

causes of infertility

A

pituitary failure - tumour, pituitary removed, can’t produce LH/FSH
prolactinoma - make prolactin inhibit LH and FSH, men and women primitive and bad contraception
azoospermia - no sperm
Testicular failure: mumps - increasing because people not taking the vaccine. Klinefelter syndrome XXY
Ovarian failure: turner’s XO- short, wide spaced nipples, shield chest
polycystic ovarian syndrome (PCOS) - more common than diabetes, too many eggs produced, infrequent periods, hyper-androgenaemia eg increased male pattern hair, acne
polycystic ovaries - increased number of enlarging ovarian follicles

59
Q

oestrogen and progesterone affect in luteal phase

A

inhibit LH and FSH (-ve feedback)

decreases when oestrogen and progesterone decrease

60
Q

effect of 17-OH progesterone

A

at end of follicular phase

enhance oestrogen’s positive feedback effect

endocrinology (12 decks)

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