Reproductive System 10b Flashcards
(43 cards)
What is spermatogenesis?
Process of sperm development, begins at puberty
Occurs within the seminiferous tubules
Reduces teh number of chromosomes to one from each pair (by meiosis)
Changes the shape of sperm so they can deliver chromosomes
What is teh initial stem cell thats starts teh process of spermatogenesis?
Spermatogonium, a diploid stem cell
Describe the process from that original stem cell in spermatogenesis.
Spermatogonium, divides into primary spermatocyte (still diploid cell), divides into secondary spermatocyte (haploid cells, there are two now), these two secondary spermatocytes (result of meiosis 1) each divide forming 4 early spermatids, all haploid and resulting from meiosis 2, late spermatids start to take on a different shape, continue to mature and gain motility in epididymis
What hormones target the testes and what effect do they have?
Luteinizing hormone: secreted by anterior pituitary
Follicle stimulating hormone: secreted by anterior pituitary, supports sperm maturation
Testosterone: important in sperm production and development of male characteristics
Where does LH bind in male reproduction?
Binds to receptors on Leydig cells (interstitial)
What cells does FSH stimulate?
Stimulates Sertoli cells in teh testes to support sperm maturation
Where does testosterone come from?
Secreted by Leydig cells of teh testes
Describe the negative feedback loop that regulates testosterone production.
Hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates anterior pituitary to secrete luteinizing hormone (LH), which stimulates production of testosterone by Leydig cells of testes
Finally, rising testosterone levels inhibit the release of GnRH from hypothalamus which decreases LH which decreases testosterone secretion
Is sperm production regulated by positive or negative feedback? How?
Negative
FSH produced by anterior pit. Makes the immature sperm more sensitive to testosterone, stimulates sperm production
High sperm count prompts the seminiferous tubules to produce inhibin, which inhibits the production of GnRH and FSH
What is the stem cell in oogenesis?
Oogonium
How does oogenesis differ from spermatogenesis (very generally)?
The timing the very different, sperms do it all in one shot whereas as in females the primary oocyte in stuck in prophase 1 until puberty where every month one of these primary oocytes will complete meiosis 1, be ovulated, and then may or may not move on to meiosis 2 if its fertilized
Naturally its much more complicated
What’s teh deal with female reproduction before puberty?
Before birth: females will have all of their oogonia (stem cells) progress to prophase 1 of teh first meiotic division and stay there
Females are born with all of their eggs stuck in prophase 1 of meiosis 1
Nothing changes until puberty
What happens in female reproductive cycle as of puberty?
Each month, a small number if these primary oocytes continue and complete meiosis 1 and only 1 becomes the secondary oocyte (the other becomes a polar body and is discarded)
Note: its a combination of FSH and LH that will cause the maturation of the egg and its ovulation
After completing meiosis 1, the secondary oocytes is ovulated, and meiosis 2 will only be carried out if fertilization occurs
How can fraternal twins happen?
If when the ovum is fertilized, another sperm also fertilizes the polar body
When does the secondary oocytes become an ovum?
Once it has undergone meiosis 2, which only occurs when sperm penetration occurs
What are teh two coordinated female reproductive cycles?
Teh ovarian cycle: changes in ovaries
Teh menstrual cycle: changes in the walls of uterine lining
When do the female reproductive cycles begin?
Starts at puberty until menopause
What are the 3 phases of teh ovarian cycle?
Follicular
Ovulatory
Luteal
Resulting in teh release of an egg
What is the role of teh follicle in all of this female reproductive stuff?
Helper cell, supports and surrounds primary oocytes
What are the steps in the follicular phase?
Ant. Pit. Release FSH and LH
-primary follicle contains primary oocyte, secretes estrogen
-completes meiosis 1, results in a secondary oocyte and a polar body
-teh mature follicle results from rapid growth (higher doses of FSH than LH)
What are the steps in the ovulatory phase?
spike in LH triggers ovulation, mature follicle ruptures, releases teh secondary oocyte
What are teh steps in teh lutéal phase?
The corpus luteum forms from the follicle cells that remain in teh ovary (teh ruptured follicle basically) and it secretes sex hormones like estrogen and a lot of progesterone that target the uterus
If pregnancy does not occur, corpus luteum degenerates
High doses of LH
What is superovulation?
Development of more than usual follicles and consequently more mature gametes
Can result from administration of FSH
What is the menstrual cycle? What controls it?
Series of changes controlled by hormones that help prepare teh uterus for a possible pregnancy
Controlled by hormones of teh pituitary glands and ovaries
