Endocrine Signalling 4 Flashcards
Where are sperm produced
Seminiferous tubules then drained into epididymis for 15 days
What 3 glands make seminal fluid
Seminal vesicles, prostate and bulbourethral gland
All androgen dependent
What do leydig cells produce
Testosterone
What do seritoli cells do
facilitate the progression of germ cells to spermatozoa via direct contact and by controlling the environment within the seminiferous tubules - gives nutrients and take away waste products.
Produces inhibin B
What are the stages of spermatogenesis
Spermatogonia —> daughter cell becomes primary spermatocyte –> secondaey spermatocyte –> spermatids (75 days) –> spermatozoa in seminiferous tubule –> spermatozoa in epidiymis (15 days)
What happens in spermiogenesis
Get tail, mitochondria mid piece, dense DNA material
What is capacitation
The process of allowing sperm to move during ejaculation
What is the feedback control in men
GnRH pulse –> LH pulse to leydig cells –> testosterone pulse –> seritoli cells, secondary characteristics, androgen-binding protein
What is the role of androgen binding protein
Binds to testosterone to keep it in the testes as it is steroid hormone it is hydrophobic so can leave cell at any point
Give some features of negative feedback in men
Inhibin on FSH
Testosterone on LH and GnRH
What secondary roles do testosterone have
Male pattern baldness
CNS - aggression
Enlarged penis
Enlarged testes
Enlarged muscles
Enlarged prostate
Deeper voice
Facial hair
What is inhibin B a marker of
Seritoli cell function (as secreted by it)
1 seritoli cell to 40 spermatogeneic cells
How many days between the first day of menstrual bleeding and LH surge
14 days (follicular phase)
What happens after the LH surge
Oocyte ovulated from the dominant follicle
What happens after oocyte ovulation
14 days of corpus luteum (luteal phase)
What occurs after the luteal phase
Secretory phase - mature endometrium is maintained by corpus luteum during luteal phase but it sheds at this point due to no HbGC hormone
What does inhibin B do in women
Inhibits FSH via negative feedback at AP
What does the inhibin B negative feedback do to these follicles
The handful of mature poteintial follicles start competing for the finite supply of inhibin B leaving one follicle alive which is ovulated
What triggers the LH surge
Oestrogen produced by the ovulated follicle
What does the corpus luteum produce
Oestrogen - drive and support endometrium
Progesterone - drive and support endometrium
Inhibin A - negative feedback
What is a key physiological change in the luteal phase
Spike in body temperature
What does LH do
Maintains the dominant follicle
What does FSH do
Stimulates follicular recruitment and development
What does oestradiol do
Supports secondary sexual characteristics
Negative feedback of FSH and LH
Where is inhibin B made
Granulosa cells
Where is inhibin A made
Corpus luteum
What is the role of inhibin B
Negative control of FSH
What is the role of inhibin A
Negative control of hypo-pituitary axis
What is the role of progesterone
Released by corpus luteum to maintain the endometrium
How do ovaries make oestrodiol
2 cell types and 2 gonadotrophins needed -
Theca cells (LH receptors found on them and when bound, uses cholesterol to make androsteindione
Androsteindione is then released by the tehca cell and given to the granulosa cell where aromatase makes esterone –> estradiol which is released to have its effects. (dependent on FSH binding)
As a follicle grows, what does it become more dependent of
FSH
Once reaches 2mm –> in competition with other follicles for ovulation (14 days)
What stops the LH surge
1 - Refractory period for GNRH receptors in anterior pituitary
2 - dominant follicle to corpus luteum which oestrogen, inhibin A and progesterone production occur which causes just big GnRH impulses
How does menstruation cause a rise in FSH again
Loss of corpus luteum results in loss of oestrogen, inhibin A and progesterone production so negative feedback is lost increasing the GnRH and FSH release
Give some targets for oestrogen
Blood clotting
Bone turnover
Breast development
Fat distribution
What regulates androgen binding protein
WIDER READING - Hansson 1976
FSH but produced by seminiferous tubules of the testis
What clears androgen binding protein
Wider reading - Ma 2015
Testosterone (aka negative feedback)
When would inhibin A and B sometimes be raised
Wider reading - Lappohn et al 1989
Ovarian tumours - granulosa cell tumour.
