MCP 22: Fertilization Flashcards
How many cells in human body?
10 trillion
How many different types of cells?
250 (including some stem cells)
oviduct
Fallopian tube-like structure in non-humans
ampulla region
where fertilization occurs in Fallopian tube
other terms for fertilization
conceptions, fecundation, syngamy
granulosa cells
cells that surround the secondary oocyte
corona radiata
collection of granulosa cells that surround the secondary oocyte, multiple sperm make contact with the corona radiata
secondary oocyte
egg is arrested in metaphase II
active forward motility
how the sperm approaches the egg, tail spins to propel it forward
hyperactive motility
other way for sperm to meet with egg, tail flails around, not as effective as active forward motility
acrosome
tip of sperm
hyaluronidase
decreases adhesions between the granulosa cells so the sperm can wiggle in
acrosin
enzyme that eats away ate zona pellucida
zona pellucida
egg shell, thick later of extracellular matrix material surrounding the oocye
theories for egg/sperm fusion
- ) sperm membrane protein fertilin binds to integrin receptors on egg 2.) sperm releasing calcium and activating tyrosine receptors on egg
* *multiple theories could be correct so the sperm has multiple avenues to merge with the egg**
fertilin
sperm membrane protein responsible for binding with egg
What happens when the sperm binds to the egg?
1.) sperm does NOT bind head on 2.) egg releases a wave of calcium upon binding
What happens after the egg releases calcium upon sperm/egg fusion?
1.) Meiosis is reactivated; forms mature ovum and second polar body 2.) signals organelles called cortical granules to exocytose contents between plasma membrane and zona pellucida
cortical granules
blocks polyspermy by hardening the zona pellucida
continuation of meiosis after fertilization
progress through S phase, nuclear material mixes once membranes fall apart, chromosomes undergo mitosis in a single cell creating a diploid organism
3 to 4 days post fertilization
1.) division continues and each cell is called a blastomere
blastomere
what each cell is called 3-4 days after fertilization until the cell reaches the morula (12-cell) phase, cells become progressively smaller because they are limited in size by the zona pellucida
morula
when the 12-cell stage is reached, compaction occurs
compaction
occurs at the 12-stage cell cycle 1.) cells begin to flatten and form junctions, differentiation begins because cells on the inside have different environments than those on the outside 3.) outer cells form Na/K ATPase pumps to set up concentration gradient
inner cell mass
cells that are pluripotent (can differentiate into anything), source of stem cell controversy, embryo develops from these cells
early blastocyst phase
formation of blastocyst occur in uterus, blastocoel cavity forms, if this doesn’t happen, zygote will degenerate
blastocoel cavity
fluid-filled cavity that forms in the early blastocyst phase, Na/K ATPase pumps create sodium gradient which causes water to rush into cell and fill bastocoel
late blastocyst phase
when the egg hatches from the zona pellucida and is ready to implant in the uterus
three layers of the uterus
endometrium, myometrium, and perimetrium
implantation in uterus
1.) hatched blastocyst implants into endometrium closest to the inner cell mass
embryonic pole
the direction that the late blastocyst implants into the endometrium
layers of the endometrium
basal, spongy and compact
basal layer of endometrium
contains its own blood supply and is not sloughed off during menstruation
timeline of hormones during early follicular phase
1.) hypothalamus secretes releasing factors that act on anterior pituitary 2.) anterior pituitary releases FSH 3.) FSH causes follicles to grow 4.) one follicle closes to the blood supply around 6-8 days will become the dominant follicle 5.) mature follicle secretes estrogen that inhibits FSH release and causes the epithelium to proliferate
timeline of hormones during the mid follicular phase
1.) dominant follicle submits estrogen for 150pg/ml for ~36 hrs and estrogen starts to have a positive feedback mechanism on FSH production 2.) more follicles produced 3.) surge in LH 4.) LH surge increases progesterone 5.) progesterone stimulates enzyme to degrade wall of follicle and release egg
timeline of hormones in luteal phase
1.) elevated progesterone levels inhibit FSH production, stops production of new follicles 2.)if not implantation occurs 12 days after ovulation, follicle degenerates, estrogen and progesterone production decreases, FSH production increases and new follicles are formed, mensus
corpus luteum
unlucky follicles that did not become the dominant follicles
What happens when implantation occurs?
corpus luteum remains intact and continues to secrete estrogen and progesterone, cells from implanted embryo (syncitiotrophoblast) will secrete human chorionic gonadotropin (hCG)on positive feedback loop on corpus luteum
syncitiotrophoblast
trophoblast differentiated into this tissue when binds to endometrium, multinucleated, dissolves connections between the endometrium and allows embryo to invade, secretes human chorionic gonadotropin (hCG)on positive feedback loop on corpus luteum
rise in body temperature
elevated levels of estrogen and progesterone raise woman’s body temperature
RU486
birth control that acts as a competitive inhibitor of progesterone, 2mg daily low dose used for contraception, high 10mg dose used for Plan B; uterus thinks no progesterone is present
twins
chances of having twins=1 in 90, chances of having triples 1 in 90 squared
dizygotic twins
2/3 of twins are dyzygotic, two separate eggs and two separate sperm, different placents
monozygotic
division occurs during the blastocyst phase when the inner cell mass divides, these cells are pluripotent, thus identical twins
differences between clones and twins
clones have shortened ends of chromosomes, are less viable, may be larger and often exhibit premature aging
cavitation
formation of blastocoel
fertilization
starts with contact between sperm and secondary oocyte, ends with fusion of paternal and maternal nuclei
zona reaction
when cortical granules on the innermost side of the oocyte plasma membrane are released into the perivitelline space
perivitelline space
between zone pellucida and plasma membrane/cytoplasm of egg
sperm plasma membrane
fuses with that of the egg, sperm head and tail enter ooctye but plasma membrane remains behind
female pronucleus
mature oocyte that forms after meiosis resumes post fertilization, second polar body also formed
formation of male pronucleus
after in the oocyte cytoplasm, nucleus of sperm decondenses, tail degenerates, and male pronucleus formed–difficult to discern male and female pronuclei, but female pronucleus is slightly larger
