Reproductive Lecture 2 Flashcards
What is an important feature of blood flow to the testes?
counter current exchanging (prevents flow from collapsing a gradient)
ex: keeping penguin feet cold
Define spermatogenesis
process of sperm production
What are the 2 processes that comprise spermatogenesis?
1) spermiogenesis (remodeling)
2) spermeation (extrusion of flagellated sperm into lumen of tubule)
What are spermatogonia?
pool of undifferentiated cells committed to differentiation
Do spermatogonia cells undergo mitosis, meiosis or both?
both (majority are mitosis, minority meiosis)
Where are the spermatids?
- near lumen of seminiferous tubules;
- attached to adjoining Sertoli cells by “tight junctions”
- connected to secondary spermatocytes by intercellular bridges
What is one of the major features of spermiogenesis?
shrinkage of cytoplasm (cap of membrane containing digestive enzymes – acrosome)
What is the function of the epididymis?
sperm maturation, reservoir for sperm, stabilize acrosome
What is the function of the prostate?
alkaline secretions (neutralize vaginal secretions) also secretes prostatic specific antigen (diagnostic use)
What secretes prostaglandins?
seminal vesicle
What do prostaglandins do?
assist with uterine contractions
What hormones stimulate the hypothalamus to secrete GnRH? Inhibit?
stimulated: norepinephrine
inhibit: dopamine, endorphins
What are the 3 hormones produced by the gonads that feedback on the HPT axis?
1) Activin (activate pituitary)
2) Inhibin
3) Follistatin
latter 2 inhibit
Do testosterone/estradiol stimulate or inhibit hypothalamus/pituitary?
inhibit
The endocrine and paracine functions of activin and inhibin are different, their namesake, however, is derived from their _____________ function
ENDOCRINE (feedback on pituitary)
Why is GnRH pulsatility so important?
continuous exposure to GnRH is inhibitory to FSH and LH (needed to stimulate gonads to produce androgens)
What happens to GnRH release in steroid users?
it is shut down (why athletes experience big crash when they come off steroids - body has to acclimate to synthesizing FSH again)
Why would you find hCG in an athlete’s blood?
stimulates testes to produce testosterone again
Leydig cells are stimulated by ____ to secrete testosterone
LH
How does LH act on leydig cells?
binds GPCR, activates PKA leading to an increase in gene transcription to support biosynthesis of testosterone
LH causes increased expression of sterol-carrier protein and sterol activating protein
What stimulates Sertoli cells?
1) androgens
2) FSH
What does FSH do when interacting with Sertoli Cells?
binds GPCR then PKA stimulates increased gene transcription to increase biosynthesis of ABP (androgen binding protein)
increases androgen receptors, increasing responses to T
activates P-450 aromatase in Sertoli cells to convert T to E2
increases growth factors to stimulate spermatogonia
increases inhibin synthesis (to feedback on it)
What is the paracrine action of inhibin?
secreted by Sertoli cells, activates Leydig cells to produce more testosterone
What is the paracrine action of activin? How does this differ from the endocrine action?
Activin inhibits T secretion but stimulates thyroid to secrete FSH and LH
Overall regulation of spermatogenesis is a balance of ____ and __________
FSH and inhibin
If spermatogenesis is too fast, what is the brake?
germ cells signal to Sertoli cells to increase inhibin
If spermatogenesis is too slow, the brake is pulled off and what happens?
decreased inhibin which leads to an increase in FSH which results in an increase in spermatogenesis
What is primarily responsible for erection?
parasympathetics
Ach and NO
What does NO do in achieving erection?
stimulates guanylyl cyclase, producing cGMP (leads to vasodilation)
Viagra acts to inhibit the phosphodiesterases the break down cGMP
ejaculation is under control of a ________ ________
spinal reflex (afferents reach sacral spinal cord S2-S4 triggering efferent somatic motor neurons via pudendal nerve)
What is hypergonadotropic hypogonadism?
increased LH, FSH with decreased testosterone, DHT)
Ex: Klinefelter’s
PRIMARY GONADAL ABNORMALITY
What is hypogonadotropic hypogonadism?
decreased LH, FSH, decreased testosterone, DHT
abnormalities in tertiary (hypothalamic) and secondary (pituitary) function
The fundamental reproductive unit of the ovary is the __________
follicle
What is responsible for maintaining hormonal support for the fetus until the placenta can?
ovaries
When do all oogonia become primary oocytes?
6 months after birth (stopped in prophase of meiosis I)
What kind of cells surround the follicle?
granulosa (surrounded by theca)
What are the stages of follicular development?
Primordial follicle —–> primary follicle ——> secondary follicle
Follicles become secondary under the influence of _____
FSH
What is the Graafian follicle?
dominant one, defined by fluid filled space in the center (antrum)
get one per month (suppresses other follicles from growing/developing)
What surrounds the oocyte?
zona pellucida (mucopolysaccharide)
What anchors the egg in the follicle so it doesnt rattle around?
cumula oophorus
What triggers rupture of the follicle?
lots of antral fluid (increased osmotic pressure)
mucopolysaccharides depolymerize
When is the initial meiotic division completed
ovulation (first polar body degenerates, secondary oocyte prevails)
What happens to the Graaffian follicle after ovulation?
becomes the corpus luteum
What is the main hormone secreted by the corpus lutuem?
protesterone
Why is the corpus luteum yello?
lipid droplets that accumulate when the theca and granulosa cells undergo leutinization
If no baby, corpus luteum becomes _______ ________
corpus albicans
Inhibin B is from the _________ _________
dominant follicle
Inhibin A is from the _________ __________
corpus luteum
What are the 3 estrogens?
1) estradiol (E2)
2) estrone (E1)
3) estriol (E3)
How is estradiol transported?
SHBG (sex hormone binding globulin)
