L34 - Reproduction 1 Flashcards
What are male reproductive functions?
spermatogenesis, hormone secretion, delivery of sperm to the female, fall asleep
What are female reproductive functions?
oogenesis, hormone secretion, reception of sperm, fertilization, gestation, parturition, lactation
When does spermatogenesis begin?
puberty
When does oogenesis begin?
fetal life
What are the characteristics of gametogenesis in males?
quiescent till puberty (mitosis stage)
4 sperm per germ cell
What are the characteristics of gametogenesis in females?
development in embryo (start of meiosis)
born with all her 1˚ oocytes
1 egg per germ cell
What are the hormones released by the anterior pituitary gland?
ACTH (adrenocorticotropin)
FSH, LH (reproduction)
TSH (thyroid)
GH (growth hormone)
What are the hormones released by the posterior pituitary gland?
vasopressin (ADH) and oxytocin
What is GnRH?
tropic hormone which releases gonadotropins
GnRH = gonadotropin-releasing hormone
What is LH?
luteinizing hormone
What is FSH?
follicle-stimulating hormone
What are the major hormones in males and females?
androgens (includes testosterone) are dominant in males
oestrogens are dominant in females
progesterone in females; ‘pro-gestation’
inhibin; negative feedback!
Which cells carry out spermatogenesis?
sertoli cells support and regulate spermatogenesis + supply androgen binding protein
leydig cells supply testosterone
How is spermatogenesis regulated?
GnRH stimulates the release of FSH and LH from the anterior pituitary gland -> LH stimulates leydig cells to release testosterone while FSH stimulates sertoli cells to release cell products which support sperm development
What is the role of testosterone?
aids in sperm development and is sent out into the rest of the body to elicit a variety of effects
How is testosterone sequestered in different parts of the body?
sertoli cells release androgen-binding protein (ABP) which binds to testosterone and sequesters it inside the testes
in the blood, testosterone binds to serum albumin and sex hormone-binding globulin (SHBG)
If you wished to reduce sperm production without inhibiting testosterone levels, you could block production of:
FSH
Is testosterone secretion continuous from puberty?
yes, provides negative feedback to LH and GnRH
Which hormones are involved in negative feedback?
inhibin and testosterone
If a man were to take testosterone supplements…
LH levels would decrease
endogenous testosterone production would decrease
What happens during the ovarian cycle?
a single follicle is selected for maturation -> as it matures, theca and granulosa cells regulate hormonal balance -> ovulation occurs and egg leaves ruptured follicle -> follicle is converted into a corpus luteum
Where do the primary hormones come from?
GnRH from the hypothalamus
FSH and LH from the anterior pituitary
oestrogen, progesterone and inhibin from ovary
How is the early to mid follicular phase hormonally controlled?
FSH stimulates a follicle to start developing
LH stimulates theca cells to release androgens -> androgens are converted into estrogens by granulosa cells -> estrogens have a local + feedback loop on the granulosa cells to ramp up estrogen production and a - feedback loop on FSH, LH and GnRH which ensures that other follicles aren’t selected
What is the role of Anti-Müllerian hormone?
reduces sensitivity of other follicles to FSH, allowing a single dominant follicle to emerge
How is the late follicular and ovulation phase hormonally controlled?
when estrogen reaches a certain level, system switches from - feedback to + feedback resulting in surges in LH and FSH -> LH surge is directly responsible for stimulating ovulation
FSH does not increase as much due to secretion of inhibin
How is the early to mid luteal phase hormonally controlled?
corpus luteum releases progesterone, estrogen and inhibin
high progesterone maintains the endometrium
inhibin decreases follicles
there is also a decrease in GnRH, LH and FSH
How is the late luteal phase hormonally controlled (when no pregnancy)?
CL spontaneously dies, low hormones, menses, higher FSH and LH -> new follicle
If follicles lost their sensitivity to gonadotropins…
GnRH/FSH/LH levels would increase and estrogen levels would decrease
