Repro. System Physiology Flashcards
four tasks of both repro systems
produce gametes
bring gametes together through copulation
combine genetic material
(gestation/parturition)
each type of gonad (primary sex organ) produces what?
ovaries and testes both produce gametes and hormones
HPG axis
Hypothalamic-pituitary-gonadal axis
fundamental relationship between these three structures
hypothalamus -> tropic hormone GRH -> hypophyseal portal system’s blood vessels -> anterior pituitary releases FSH & LH -> gonads release steroidal sex hormones -> systemic circulation -> target cells
negative feedback react with receptors to inhibit hypothalamus’s release of GRH, anterior pituitary’s release of FSH and LH
HPG axis and puberty
prepubescent children’s circulating sex hormones are very low but still enough to exert negative feedback on hypothalamus,
as puberty approaches, hypothalamus’ cells become less sensitive, so GRH increases because they’re less inhibited
need continually larger amounts of hormone to inhibit cells in hypothalamus, so GRH continues until adult pattern achieved
What happens during mitosis in spermatogenesis?
(first step), spermatozoa make 2 identical diploid copies and A stays by basal lamina while B gets pushed down to grow into a primary spermatocyte
What happens during meiosis I of spermatogenesis?
primary spermatocyte divides into two different smaller haploid daughter cells aka secondary spermatocytes
what happens during meiosis II of spermatogenesis?
each of the two secondary spermatocytes divides into two different smaller haploid cells called spermatids
what does LH act on in males and what are the results?
interstitial cells, telling them to release testosterone, some of it will be grabbed up by Androgen Binding Protein so it can enter the testis and drive events of spermatogenesis
What does FSH act on in males and what are the results?
sertoli cells, tells them to increase production of ABP so that the local concentration of testosterone can stay high for spermatogenesis
What prevents the testes from becoming overloaded with sperm cells?
negative feedback - large amounts of sperm in the lumen stimulate sertoli cells to release inhibin, which acts on the anterior pituitary gland to inhibit the release of more FSH and LH
testosterone’s effects on body other than testes
converted into other hormones at tissue level by local enzymes,
converted → estradiol in some brain neurons, secondary sex characteristics develop, axillary and pubic hair, sex drive in women, hypersecretion can cause super sex drive, early development of sex organs and secondary sex characteristics, females develop beard and masculine distribution of body hair, and clitoris grows
cognition, memory, sex drive, bone marrow, bone density, collagen, bone density, sperm count, prostate growth, erectile function
erection
arterioles usually constricted, sexual excitement causes CNS (cerebrum) parasympathetic neurons → local release of NO → smooth muscle relaxation → filling with blood → enlargement & stiffening → veins draining penis are cut off to allow maintenance
ejaculation
spinal reflex from sympathetic nerves → contraction of glands → presence of semen in urethra → bulbospongiosus series of rapid contraction → semen leaves body ~11 mph
ED
erectile dysfunction affects about half of men over 40
cardiovascular disease (obesity)
too little NO, can’t fill corpora cavernosa with blood
sildenafil (Viagra) keeps NO around longer and enhances effect of existing NO
In primary oocytes, meiosis I arrests in ___ and can resume years later if oocyte is recruited
prophase I
in secondary oocytes, meiosis II arrests in ___ and only continues if fertilization occurs
metaphase II
what do granulosa cells of follicles release?
liquor folliculi and estrogen
when is meiosis I completed?
just before ovulation (release of secondary oocyte)
corpus luteum (follicle leftover after ovulation) releases lots of which hormone?
progesterone (to maintain possible pregnancy)
fertilized egg implants in uterus and releases HcG and tells corpus luteum around
corpus albicans
corpus luteum becomes a scar on ovary if no pregnancy
atresia
99.9% of follicles never recruited, undergo apoptosis
what makes a dominant follicle different?
follicle sensitive to even falling levels of circulating FSH that completes meiosis I and freezes in metaphase II of meiosis II
spermatogenesis vs. oogenesis, including # of gametes per meiotic division
4 equal sized sperm vs. 1 lg ovum and 2-3 sm. polar bodies
sustentocytes (sertoli) : spermatogenesis :: granulosa cells :
oocyte
one sertoli cell supports many sperm; many granulosa cells support one oocyte
dominant hormone in each phase of ovarian cycle
follicular phase - estrogen (granulosa cells)
luteal phase (always 14 days) - progesterone (corpus luteum)
estrogen spike during follicular development triggers anterior pituitary to release ___
luteinizing hormone, which triggers ovulation
FSH and LH at ovary
LH stimulates thecal cells to increase production of androgens →
FSH stimulate granulosa cells to convert androgens → estrogen → negative feedback & inhibin → only dominant follicle can withstand low level of FSH
When does ovulation occur in the uterine cycle?
at the end of the proliferative phase (around day 14)
puberty onset
cells of the hypothalamus responsible for GnRH become less sensitive to inhibition from estrogen & testosterone, so you need increasingly higher levels of sex hormones to inhibit GnRH, leading to higher levels of sex hormones in the body and their various effects
what is mitosis for?
growth and repair, which is why it makes 2 genetically identical cells (same size, same genome)
how many chromosomes do you find in a human liver cell vs. a human sperm cell?
46 chromosomes in somatic (non-gamete) cells
23 chromosomes in gamete cells
metaphase of meiosis I is significant for genetic variability because
tetrads, crossing over
what else does sperm cell have besides genetic material
package of enzymes near nose for entering ovum, motor proteins in flagella to move (no cytoplasm)
spermiogenesis vs spermatogenesis
spermiogenesis is late spermatogenesis after mitosis and meiosis I-II, whereas spermatogenesis is the whole process from spermatogonia → spermatozoa
FSH vs LH in males
FSH → sertoli cells to increase ABP and get testosterone into seminiferous tubule to drive spermatogenesis
LH → interstitial cells to increase production of testosterone (some released locally, some systemic)
influence of systemically circulating testosterone on male body
increased RBC production (higher hematocrit), larger and denser skeleton, positive feelings, better cognition & memory, libido, body hair and more collagen, muscle mass
stimuli for erection (2 types)
top-down (cerebrum integrates 5 senses’ input) OR
direct touch stimulation
what makes arteries of penis different from others
dual-innervated; parasympathetic innervation of arteries → release NO → smooth muscle relaxation
difference between primary and secondary oocyte
primary is diploid, secondary is haploid (finished meiosis I)
meiosis I completes in a ___ follicle just before ___
meiosis I completes in an antral follicle just before ovulation
what hormone do follicles produce? effect regarding FSH?
follicles produce estrogen → negative feedback → lower FSH levels → only most sensitive follicles continue development
estrogen has a very brief transient feedback when?
super high levels of estrogen briefly have a positive feedback effect and lead to FSH and LH spikes right before ovulation
ovarian cycle (2 phases)
- follicular phase day 0-14
- day 0-5 is menstruation
- luteal phase 14-28
menstrual cycle (3 phases)
1-5 menstrual
6-14 proliferative phase (proliferating endometrium)
15-28 secretory (because high levels of secretion from endometrial glands to maintain it)
