Chapter 1: Getting Ready for Pregnancy Flashcards
Gametogenesis Phase 1:
primordial germ cells originate in endodermal layer of yolk sac (develop outside embryonic tissues)
recognizable 24 days after gestation-large and high [alkaline phosphatase]
migrate through dorsal mesentry and enter primitive gonads
teratomas: misdirected germ cells, pluripotent; occur in oral, sacral areas and behind the heart
Phase 2: mitotic division increases cellular numbers FEMALES
in females, oogonia: mitotically active female germ cells; egg cell that is not yet in meiosis
intense meiotic activity from 2-5 months of pregnancy with 7 million produced
most undergo atresia
atresia of egg cells
natural degradation due to lack of space, nutrients, chromosomal stability, etc.
phase 2: MALES
spermatogonia divide up and take up space in gonads; division not as intense
seminiferous tubules become lined with germinative layer
at puberty, subpopulations undergo periodic waves of mitosis
type A spermatogonia
continue to undergo mitosis (stem cells)
type B spermatogonia
undergo meiosis; arise from type A
connected by cytoplasmic bridges surrounded by Seritoli cells
phase 3: reduction of chromosomal number by meiosis
2n 2c before meiosis——–double chromosomal number————2n 4c ———1st meiotic division ———CENTROMERE DODES NOT SPLIT——– 2 (1n 2c)—–2nd meiotic division ——– 4 (1n 1c)
1n 1c = truly haploid cells
reductional division
prophase 1: prolonged, homologous recombination within chromosomes
metaphase I: tetrads line up at metaphase plate
anaphase I: no centromeric division; daughter cells genetically unequal (1n 2c chromosomes contain 2 chromatids connected by a centromere)
telophase I: incomplete cellular division in spermatid production
equatorial division
prophase II, metaphase II
anaphase II: centromeric division; daughter cells genetically unequal (1n, 1c)
telophase II: results in production of 4 truly haploid gametes in sperm
crossing over
not purely random; occurs a certain hot spots
hypermethylation occurs where DNA strand will break and later be repaired after crossing over
cohesin
helps hold sister chromatids together during division
condensin
important for compaction of chromosomes
women 1st meiotic division
begun in late fetal period; completed immediately prior to ovulation
2dary oocyte and polar body: oocyte begins second meiotic division but encounter meiotic block that can only be surpassed with fertilization by spermatozoon
meiosis in men
does not begin till after puberty and not all spermatogonia enter meiosis at the same time
blocks to maturation in women
cAMP (from oocyte and follicle) gets converted into 5’ AMP by PDE3A, which is inhibited by cGMP produced by follicular cells
cAMP also inhibits MPF (maturation promoting factor)
gap junctions
form between primary oocyte and follicular cells
allows for transport of materials
structure of egg and follicle
nucleus–oocyte–zona pellucida–granulosa cells—membrane granulosa—theca interna — theca externa
oocyte
relies on diffusion and gap junctions to survive; microvilli also play a role
zona pellucida
prominent, translucent, noncellular membrane (glycoproteins, glycosamines, sperm receptors )
membrane granulosa
basement membrane of granulosa cells (capillary barrier)
theca interna
highly vascularized tissue;
have LH receptors
produce androgens in response to LH surge (converted by granulosa cells into 17beta-estradiol which stimulates LH receptors on granulosa cells)
secrete angiogenesis factor to support follicular growth
antrum
develops in the secondary follicle
cavity filled with liquor folliculi
liquor folliculi
contains serum proteins in low concentrations, enzymes, hormones, proteoglycans with low negative charge to attract water
cumulus cells
cells immediately surrounding the oocyte
don’t develop hormone receptors but do help release ovum at time of ovulation
mural granulosa cells
cells between antrum and membrane granulosa
develop normally with hormone receptors
activin
works with FSH to signal granulosa cell proliferation
theca externa cells
connective tissue-like capsule
granulosa cells
respond to FSH by producing estrogens; proliferation under activing and FSH
produce aromatase (converts androgens into 17beta-estradiol)
LH surge
signals the resumption of meiosis
LH–cumulus cell—(shut down gap junctions)–reduces transfer of cAMP and cGMP from cumulus into ovum–activation of PDE3A—(breakdown of intraoocyte cAMP into 5’AMP)—-activation of MPF–resumption of meiosis
inhibin
allows for the formation of one dominant follicle
7 days before ovulation one of the follicles becomes FSH independent and secretes inhibin which shuts of secretion of FSH from the pituitary thus killing all the other follicles still dependent on FSH
graafian follicle
at or just prior to ovulation, 1st meiotic division is complete
2dary oocyte and polar body within cumulus oophorus
oocyte factors cause cumulus cells to respond to gonadotropic hormones by hyaluronic acid production
female hormone wire diagram
[see paper flashcard]
retinoic acid
stimulates entry into meiosis in males
Seritoli cells
“nurse cells” ; surround the sperm and protect them from immune system
help sculpt sperm into mature cells
beginning of spermatogenesis
spermatogonia sequestered at the bottom of seminiferous epithelium by Seritoli cells
once type B progeny (primary spermatocytes) finish leptotene stage of first meiotic division, they pass through Sertoli cells into seminiferous tubules
Seritoli cells form blood-testis barrier ; when spermatogonia begin meiosis they are immunologically different from the rest of the body
produce in advance molecules that are needed at later periods when change occurs rapidly, like protamines
spermiogenesis
spermatids to mature spermatozoa
- reduce size of nucleus and condense DNA by replacing histones with protamines
- cytoplasm moves away from nucleus
- condensation of Golgi to form the acrosome
- flagellum grows out of centriolar region
- mitochondria spiral around proximal part of flagellum
- plasma membrane at head of sperm arranged into separate molecular domains
- remainder of cytoplasm (residual body) moves away from nucleus and is shed (phagocytozed by Sertoli cells)
at this point the sperm are not yet motile
takes 64 days
biochemical maturation of sperm
glycoprotein coating and surface modification in epididymis
prevents fertilization; stops sperm from mating with the first cell they encounter
capacitation
removal of glycoprotein coat to allow fertilization
male hormone wiring diagram
[see paper flashcard]
ICSH
interstitial cell stimulating hormone in males
chemically identical to LH in females
LCSF
Leydig cell stimulating factor; increases secretion of ICSH
ABP
androgen binding protein; together with testosterone promotes spermiogenesis
histones vs. protamines
histones contain Lys(+) (-)DNA
Protamines contain Arg(+), Cys (capable of forming disulfide bridges)
Rule of 60s
numerical evaluation of whether or not you’re sterile
need to…..
- produce 60 million sperm/mL
- 60% of 60 million must be motile
- 60% of motile must be structurally normal
20 million viable sperm/mL to be fertile
seminiferous tubules vs. epididymis
seminiferous: structural maturation
epididymis: biochemical maturation (glycoprotein coating and surface modification)
uterine tube
three sections: ampulla, isthmus, intramural
fimbriae project out towards ovary from the open infidibulum of uterine tubue
intramural segment
embedded within uterus wall, thin lumen and mucus that varies and regulates passage of sperm/bacteria into uterus
isthmus
temporary storage of sperm;
participates in final stages of functional maturation of sperm cells
endometrium
uterine mucosa
receives and maintains the embryo
myometrium
smooth muscular wall used to push out the fetus
functional layer of endometrium
shed at each period
basal layer of endometrium
remains intact at each period
general structure of uterus
- columnar surface epithelium
- uterine glands
- specialized connective tissue stroma
- spiral arteries that coil from basal layer towards the surface
cervix
mucousal surface which isn’t typical endometrial epithelium;
varies throughout the cycle
rich in glycoprotein
vagina
stratified squamous epithelium;
deposits of glycogen that are broken down to increase acidity
hypothalamus
releases GnRH
anterior pituitary
GnRH causes release of FSH and LH (gonadotropic hormones); also prolactin (inhibited by dopamine)
posterior pituitary
oxytocin released
ovaries and placental hormonal control
granulosa cells take theca interna cell produced androgens and convert them into 17beta-estradiol
after ovulation, progesterone produced by corpus luteum
placental produces its own progesterone and estrogen; human chorionic gonadotropin, human placental lactogen (acts on corpus luteum)
target tissue hormonal control
changes in number of ciliated cells, smooth muscle activity in uterine tubes
changes in endometrial lining
cyclical changes in glandular breast tissues
estrogen primes target tissues for progesterone by inducing progesterone receptors
Proliferative Phase (days 5-14)
estrogen dominated
uterine lining reepithiliazed
uterine glands elongate
endometrial stroma thickens
spiral arteries grow towards surface
cervix secrets E mucus to let sperm pass
high % of uterine tubes becomes ciliated and smooth muscle activity increases
fimbriae move closer towards end of stage
high levels of estradiol produced by follicle increase responsiveness of anterior pituitary to GnRH and increase in GnRH leads to LH surge (the signal for ovulation); granulosa cells now produce progesterone
Secretory Phase (14-28)
after LH surge, increase in basal body temperature
estrogen and progesterone in blood, smooth muscle contraction to move ovulated egg towards uterus
progesterone primes endometrium for implantation
spiral arteries grow towards surface
decrease in mitotic activity of endometrial cells
cervical mucus becomes thick
vaginal epithelium now thinner
endometrium of uterine tubes undergoes regression
no pregnancy effects
inhibin produced by granulosa cells
decrease in LH and FSH
regression of corpus luteum
estrogen vs. progesterone
estrogen responsible for STRUCTURAL developments
FUNCTIONAL developments happen with progesterone
