MCAT Biology Ch5: Embryology Kap Flashcards
cleavage
moving from fallopian tube => uterus to implanation => UNDERGOES RAPID MITOTIC CELL DIVISION (rapid)
first one creates an embryo
although several rounds of mitosis, total size of embryo remains unchanged during first few divisions
cells inc. two ratios: nuclear to cytoplasmic and SA to vol. => cells inc. area for gas nutrient diffusion relative to overall volume.
indeterminate
results in cells that can still develop into complete organisms.
determinate
cells whose fates are determined
differentiating into a certain type of cell
differentiating
results in CERTAIN type of cell
two types of cleavage
indeterminate or determinate
1st, 2nd, 3rd cleavages occurs
32, 60, 72 hours
at this point, 8 celled embryo completed to uterus
morula (cleavage)
several division occurs, the embryo becomes a solid mass of cells
blastulation (cleavage)
after morula
forms blastula
blastula (cleavage)
when implants outside of uterus => ectopic pregnancy (most in fallopian tube) => inviable => if embryo doesn’t spon. abort => tube may rupture => hemorrhaging
blastocoel (cleavage)
hollow, fluid-filled inner cavity of blastula
blastocyst (cleavage)
mammalian blastula
consists of two noteworthy cell groups: trophoblast and inner cell mass
two cell groups of blastocyst (cleavage)
trophoblast and inner cell mass
trophoblast (cleavage)
surround blastocoel and give rise to chorion, and later placenta
inner cell mass (cleavage)
protrudes into blastocoel and gives rise to organism itself
early developmental stages
cleavage, implantation, gastrulation, neurulation
implantation
blastocyst in uterine wall => blastocyst implants endometrium
endometrium (implanation)
prepared in anticipation, where blastocyst implants here
progesterone (implanation)
steroid hormone promote proliferation of (endometrial) mucosal layer to help embryo implact
key step of implanation
embryonic cells secrete enzymes that burrow into endometrial lining to allow for implantation => form connection to maternal circulation for nutrient and gas exchange
implantaton like tree
seed (embryo) into ground (endometrium) => make sure soil is fertile (progestrone to endometrium)
shovel to plant seed in ground (proteolytic enzyme allow embryo to settle in uterine wall)
tree generate roots (placenta) => gas and nutrient exchange w/ soil (endometrium)
gastrulation
generation of 3 distinct cell layers
gastrulation in sea urchins
begins w/ small invagination in blastula => cells continue moving toward invagination => elimination of blastocoel => gastrula
gastrula (gastrulation )
two-layered cup form after elimination of blastcoel
endoderm (gastrulation)
inner cell layer
ectoderm (gastrulation )
outer cell layer
cells migrate over the neural tube and crests to cover rudimentary nervous system
archenteron (gastrulation )
cavity created by deep invagination
later develops into gut
blastophore (gastrulation )
opening of archenteron
deuterostomes (gastrulation )
in humans, blastopore develops into anus
protostomes (gastrulation )
blastopore dvelops into the mouth
mesoderm (gastrulation)
eventually some cells also migrate into area between ectoderm and endoderm
parts of ectoderm (gastrulation )
attract o derm
parts of mesoderm (gastrulation)
“means” o derm, we get from place to place in world
part of endoderm (gastrulation)
“endernal” orgams
long tubes running from mouth to anus (digestive tract), organs attached to it (accessory organs of digestion)
gives rise to the lungs
cleavage
single cell zygote => several mitosis occur (total size of embryo same) => several division becomes morula => blastulation
embryonic stem cells
derived from portion of very early stage emybryo => entire body (retain pluripotent ability to form any cell type)
cell fate
less than a week after human egg fertilized => developing embryo (blastocyst which only an outer cell mass, in preg. becomes placenta, and inner cell mass, which becomes fetus) => in womb, cells multiply
making embryonic cells
create by remove inner cell mass from blastocyst
ICM on plate containing feeder cells => attaches => few days, new cells grow out of ICM => form colonies
two criterias of ES cells
- display markers
- undergo several generations of cell division, or passages, => show that they constitute a stable, or immortalized, cell line
selective transciption of Somatic cells DNA (gastrulation)
of the genome (only genes for eye are tunred on in the eye.
often related to concept of induction => ability of certain group of cells to influence the fate of other nearby =>
inducers (gastrulation)
selective transcription process mediated by these chem, substances
passed from organizing cells to responsive cells
neurlation
once three germ layers => DEVELOPMENT OF NERVOUS SYSTEMS CAN BEGIN
nervous system derived from neurulation
cells migrate inward => notochord => induce group of ectodermal cells to slide inward to form neural folds => surround neural grove => grow together one another => neural tube => CNS
notochord
rod of mesodermal cells, forms along the long axis of organism
induce group of ectodermal cells to slide inward to form neural folds
neural folds
induce group of ectodermal cells to slide inward to form
surround neural groove
neural tube
neural folds grow toward one another until they fuse into this
neural crest cells
tip of each neural fold
cells migrate outward to form PNS (sensory ganglia, autonomic ganglia, adrenal medulla, Schwann cells
fetal respiration
nutrient and gas exchange w/ maternal ciruclation necessary part of fetal development
two structures of fetal development
placenta and umbilical cord
placenta
primarily formed from chorion
organ where nutrient, gas, and waste exchanges occur; simplest way is through diffusion in fetus
crucial that no mixing of maternal and fetal blood (may have diff. bloods) => diffusion
higher P(oxygen) in maternal blood than in fetal blood
waste materials and CO2 move in opposite direction
endocrine organ, since produces progesterone, estrogen, and human chorionic gonadotropin, all essential for maintaining pregnancy (266 days)
chorion
placenta primarly formed from an extra-embryonic membrane
develops from trophoblast cells
outermost embryonic layer, completely surrounds the other membrane, providing added level of protection
human umbilical cord
and vessels provide attachment to chorion and nutrition for fetus
surround by jellylike matrix
initial connection of fetus to mother
three extra embryonic membranes of fetal respiration
allantois, amnion, yolk sac
allantois
surround by amnion
amnion
thin, tough membrane filled w/ amniotic fluid
amniotic fluid
shock absorber during pregnancy and labor
yolk sac
site of blood vessel development
chorionic villi
eventually grow into placenta
support maternal fetal gas exchange
amniocentesis
aspirating amniotic fluid by inserting a thin needle into amniotic sac
amniotic fluid
contains fetal cells
can be examined for chromosomal abnormalities and sex determination
can result in genetic aberrations like Down Syndrome
fetal hemoglobin Hb-F
fetal blood cells equipped w/ this, which exhibit greater affinity for oxygen than does maternal (adult) hemoglobin, known as Hb-A
Hb-A
maternal (adult) hemoglbin
placenta barrier
immune protection
foreign particles and bacteria too large to cross by diffusion, however not the case for virus, alcohol, toxins
two important organs that are underdeveloped in fetus and rely on placenta
lungs and liver
fetus lungs
not able to oxygenate circulating blood
are suspended in aq. amniotic fluid => no air to take in
oxygen comes from maternal circulation => diffuse through placenta vessel
two fetal shunts keep blood away from LUNGS by rerouting blood w/in heart
foramen ovule and ductus arteriosus
foramen ovule
connects right and left atria
blood entering superior vena cava => right atrium => left atrium => out of aorta into systemic circulation
pressure differential:
-pressure higher in right atrium since will spon. down pressure gradient
gradient reverse in adults => forman ovale shut after birth
ductus arteriosus
present to shunt leftover blood from pulmonary artery to aorta
works like forman ovale => pressure right fetal heart is higher that that of the left
patent ductus arteriosus (PDA) => stays open after birth
-direction of blood flow through PDA will be determined by relative resistance of pulmonary and systemic circulation => if cont. => neonate will turn blue since deoxygenate venous blood bypasses lung and mixes w/ oxygenated blood being pump to body through aorta
fetal liver
underdeveloped, can’t fully able to carry out adult taks in utero
since placenta capable of pitching during gestation, blood returning from placenta via umbilical vein is rerouted to inferior vena cava via this
even though needs a lot of O2, it prevents from stealing oxygen from designated from rest of the body => liver has own reserves from arteries leaving the heart.
umbilical arteries
carry blood away from fetus
carry deoxygenated blood
umbilical vein
blood toward the fetus
carry oxygenated blood
human pregnancy
266 days
divided into 3 trimesters
gestation rule
larger the animal, longer the gestational period, and fewer the offspring
first trimester of pregnancy
end of third month:
1. fetus abou 9 cm long
first trimester of pregnancy (first week)
major organs develop
- heart beats to beat approx. 22 days
- eyes, gonads, limbs, and liver start to form
first trimester of pregnancy (five weeks)
- embryo is 10 mm length
first trimester of pregnancy (six week:)
- 15 mm length
first trimester of pregnancy (seventh week)
- by this time, cartilaginous skeleton begins to harden into bone
first trimester of pregnancy (eight week)
- most organs have formed
- brain fully developed
- embryo = fetus
first trimester of pregnancy (3rd month)
fetus about 9 cm long
second trimester of pregnancy
fetus undergoes amount of growth
begins to move around in amniotic fluid
toes and fingers elongate
end of sixth month - fetus measures 30 to 36 cm long
third trimester of pregnancy
7th and 8th month = cont. rapid growth and further brain development
9th month - antibodies transported by highly selective active transport from mom to fetus for protection against foreign matter, in prep outside of womb
growth rate slows and fetus becomes less active since less room to move about
vagina childbirth
by rhythmic contractions of uterine smooth muscle, coordinated by prostaglandins and peptide hormone oxytocin
3 basic phases to childbirth
- cervix thin out and amniotic sac ruptures (water breaking)
- strong uterine contraction => birth of fetus
- placenta and umb. cord are expelled (afterbirth)
monozygotic twins
identical genomes because both originate from indeterminately cleaved cells of same embryo
embroyo w/ blasted out cavity
this is blastula
adrenal cortex
derived from mesoderm
adrenal medulla
derived from ectoderm (since contains some nervous tissue)
spinal bifida
failture of neutral tube to close
zygote
undergoes several rapid divisions -> determinate cleavage
indeterminate cleavage
generation of identical twins
gasturalation
neuralation occurs during this
fetal respiration
occurs in placenta and not in developing lungs
ductus venosus
since placenta capable of pitching during gestation, blood returning from placenta via umbilical vein is rerouted to inferior vena cava via this
even though needs a lot of O2, it prevents from stealing oxygen from designated from rest of the body => liver has own reserves from arteries leaving the heart.
ductus venosus
fetal shunt of liver
fetal circulation contains 3 shunts
ductus venosus, foramen ovale, ductus arteriosus
gestation
consists of three trimesters of 3 months each