Flashcards in Lecture 31 Reproductive Deck (37)
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1
Organs
gonads = testes + ovaries
ducts
accessory glands
external genitalia
2
Meiosis
46 chromosomes (2n, diploid) → 23 chromosomes (n, haploid)
3
46 Chromosomes
when does DNA replicate
22 homologous pairs of autosomes + 1 pair of sex chromosomes (XX = female, XY = male)
DNA replicates prior to meiosis; each chromosome is duplicated, consists of 2 sister chromatids
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Meiosis I
homologous pairs separate, 2n (duplicated) → n(duplicated)
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Meiosis II
sister chromatids separate, n (duplicated) → n (single chromosomes)
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male
1 primary spermatocyte (2n) → → 4 sperm cells (n)
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female
1 primary oocyte (2n) → 1 egg cell (n) … → 1 fertilized egg + polar bodies
8
Spermatogenesis
occurs in seminiferous tubules of testes
spermatogonia → primary spermatocyte → secondary spermatocytes → spermatids → sperm
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Sertoli cells
support developing spermatocytes + endocrine function
10
blood testis barrier
tight junctions between Sertoli cells form barrier to immune system
11
hormonal control
general pattern
hypothalamus: GnRH → anterior pituitary: FSH & LH → gonads: steroid sex hormones + others
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FSH
stimulates gamete production in male and female
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LH
stimulates secretion of sex hormones by gonads and stimulates ovulation in females
14
Steroid sex hormones
♂: testosterone, DHT; ♀: estrogen [estradiol], progesterone
- stimulate gamete production, overall reproductive function, development
of reproductive organs and secondary sexual characteristics
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Negative feedback
Negative feedback control regulates hormone levels in males and partly in females
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Positive feedback
Positive feedback control triggers ovulation in females
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Hormonal Control of Spermatogenesis
Sertoli cells
Leydig (interstitial) cells
Negative feedback control
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Sertoli cells
respond to FSH, support developing spermatocytes
- androgen binding protein (ABP) binds and concentrates testosterone
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Leydig (interstitial) cells
produce testosterone in response to LH
- testosterone binds to ABP in Sertoli cells → promotes spermatogenesis
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Negative feedback control
(Spermatogenesis)
inhibin - secreted by Sertoli cells, inhibits FSH secretion
testosterone inhibits GnRH and LH secretion
21
Oogenesis
occurs in ovarian follicles in ovaries
follicular cells (granulosa cells and theca cells) surround a developing egg cell (oocyte)
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Follicle
primary follicle → secondary follicle → mature follicle → (Ovulation) corpus luteum
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Egg
oogonia → primary oocyte → (meiosis 1) secondary oocyte (egg) → (requires fertilization, meiosis 11)
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Ovarian Cycle
follicular phase (day 0-14)
ovulation (day 14)
luteal phase (day 14-28)
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follicular phase
growth and maturation of follicle, oocyte goes through meiosis I
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ovulation
egg bursts through wall of ovary, swept into uterine tube
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luteal phase
corpus luteum forms from remaining follicle cells;
- corpus luteum continues to secrete estrogen and progesterone;
degenerates at the end of the cycle unless fertilization occurs
28
Uterine Cycle
menses (0)
proliferative phase (14)
secretory phase (28)
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menses
- uterine lining (endometrium) is sloughed off and discharged
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