concept 2b development Flashcards
ampulla
widest part of the fallopian tube
where fertilization occurs
fertilization
sperm binds to the secondary oocyte and releases acrosomal enzymes that enable head of sperm to penetrate though the corona radiata and zone pellucida to penetrate the oocyte
acrosmal apparatus
formed when the sperm comes into direct contact with the secondary oocytes cell membrane
tube like structure
extends to and penetrates the cell membrane
this allows the pronucleus to enter the oocyte once meiosis II is completed
coritcal reaction
release of calcium ions
happens after penetration of sperm thought the cell membrane
calcium ions depolarize the membrane of the ovum
2 purposes: prevents fertilization of ovum by multiple sperm cells and increased calcium concentration increases metabolic rate of newly formed diploid zygote
fertilization membrane
depolarized and impenetrable membrane
formed by the cortical reaction
dizygote twins
fraternal twins
form from fertilization of 2 different eggs released during one ovulatory cycle by 2 different sperm
each zygote will implant in uterine wall and develops own placenta
monozygotic twins
identical twins
form when single zygote splits into 2
have identical genetic make up
if division is incomplete may result in conjoined twins
cleavage
rapid mitotic cell divisions of the zygote as it moves to uterus for implantation
many rounds of division occur but cell remains the same size
2 types: indeterminate and determinate
indeterminate cleavage
results in cells that can still develop into complete organisms
determinate cleavage
results in cells with fates that are already determined
these cells are committed to differentiating into certain types of cells
morula
embryo has undergone several divisions
solid mass of cells
has about 8 cells
blastula
morula undergoes blastulation
a hollow ball of cells with fluid-filled inner cavity called the blastocoel
trophoblast cells surround the blastocoel and give rise to the chorion and later the placenta
inner cell mass protrudes into the blastocoel and give rise to the organism itself
chorion
extraembryonic membrane that develops into the placenta
developed from the trophoblastic cells when they implant into the endometrium
chorionic villi
formed from trophoblasts
microscopic fingerlike projections that penetrate the endometrium
umbilical cord
connects the embryo to the placenta
consists of 2 arteries and one vein encased in gelatinous substance
yolk sac
supports the embryo until the placenta is functional
site of early blood cell development
allantois
involved in early fluid exchange b/w the embryo and the yolk sac
umbilical cord is formed from remnants of yolk sac and the allantois
surround by the amnion
amnion
a thin tough membrane filled with amniotic fluid
fluid serves as a shock absorber during pregnancy, lessening the impact of material motion on the developing embryo
gastrulation
generation of 3 distinct cell layers
further development after cell mass implants
results in gastrula
gastrula
embryonic stage characterized by the presence of ectoderm, mesoderm, and endoderm
archenteron
central cavity in the gastrula stage of embryological development
it is lined by endoderm and ultimately gives rise to the adult digestive tract and the gut
opening is called the blastopore which develops into the anus
primary germ layers
ectoderm
mesoderm
endoderm
ectoderm
develops into: epidermis
hair
nails
epithelia of nose, mouth, and lower anal canal
lens of the eye
nervous tissue (including adrenal medulla)
inner ear
*“attracto”derm–> develops into the things that attract us to others
mesoderm
develops into: musculoskeletal system
circulatory system
most excretory system
gonads
muscular and connective tissue layers of digestive and respiratory systems and adrenal cortex
*“means”oderm–> mean of getting around as an organism
endoderm
develops into: epithelial linings of the digestive and respiratory tracts, including lungs pancreas thyroid bladder distal urinary tracts parts of the liver *linings of "endernal" organs
selective transcription
only genes needed for that particular cell type are transcribed
how cells develop into distinctly different cell types
often related to the concept of induction
induction
ability of one group of cells to influence the fate of other nearby cells
mediated by chemical substances called inducers which diffuse from organizing cells to responsive cells
neurulation
development of the nervous system
after the 3 germ layers are formed
nervous system derived from the ectoderm
stage 1 of neurulation
a rod of mesodermal cells called the notochord is developed along the long axis of the organism like a primitive spine
stage 2 of neurulation
notochrod induces a group of overlying ectodermal cells to slide inward to form neural folds which surround the neural groove
stage 3 of neurulation
neural folds grow towards one another until they fuse into a neural tube, which gives rise to the central nervous system
at the tip of neural fold are neural crest cells, which migrate to form the peripheral nervous system and specific cell types
ectodermal cells migrate over the neural tube and crest to cover the rudimentary NS
teratogens
substance that interfere with development
cause defects or even death of developing embryo
