Embryology Flashcards
where does the release oocyte go? where does the corpus luetum go?
fallopian tube; stays in uterus
what forms appendicular skeleton
somatic lateral plate mesoderm
Acipal Ectoderm Ridge
thickening of ectoderm on distal end of limb bud that induces proliferation and growth of limb
what forms intervertebral discs
mesenchymal cells dervied from notocord between cephalic and caudal
Phase 1 of fertilization
300-500 sperm pentrate corona radiata 1 sperm pentrates egg after coat on head degrades corona radiata.
Amniotic cavity
formed by epiblasts in week 2 (day 8). a cavity formed by epiblast and cytotrophoblasts.
what happens as corpus leutrum degenerates?
tapers off the release of estrogen and progesterone and endometrium lining soughs off (menstruation)
morula
16-32 cell stage at day 4
ectopic pregnancy
blastocyst impacts in peritoneal cavity, mesentery, surface of ovary instead of uterine wall
myotome
derivative of somite gives rise to skeletal muscle
oropharyngeal membrane
tightly adhered region where mesoderm cannot intrude. Future mouth
proneucleus
nucleus in the oocyte that are haploids; one is from sperom and one is from oocyte. They fuse to form a diploid zyogte
dorsal neural crest cells
melanocytes - skin and hair follicles
sperm-oocyte membrane fusion
when cell membranes fuse and nucleus of sperm is injected into oocyte and triggers meiosis II
sclerotome
deriviative of somite. gives rise to vertebrate surround neural tube and noto cord
caudal neuropore
is caudal edge of neural tube folding. gives rise to spinal cord
what forms axons from spinal ganglion
ventral neural crest cells
what becomes mid-gut
sphlonachonpluere folding
what do cranial somites form
neurcranium or skull bone
primitive groove function
epiblast cells invaginate through primitive groove to form mesoderm and endoderm. Epiblast cells on top differentiate into ectoderm.
primitive pit purpose
epiblast cells invaginate to from notocord, which grows to oropharyngal membrane.
what trigger the LH release?
increase leveled of estrogen.
formation of three germ layers
formed by migration of epiblast cells through primitive streak
what do the rest of the somites form?
mytome or sclerotome, dermatome
what happens day 5?
morula enters uterine cavity and fluids penetrate zona pllucida into innercell space to form a single cavity called a blastocele
cranial nueropore
leading edge of cranial folding. gives rise to brain.
neural groove formation
rising of nueral plate (ectoderm) and inside sinks to from the neural groove
hind gut
formation from caudal folding
primitive streak formation
formed by thickening of epiblast layer due to epiblast proliferation from cranial to caudal
what happens when primitive streak degenerates too soon?
sirenomella, or mermaid like. undifferentiated lower limbs and other organs
week 2 goals
implantation of blastocyst, establish uteroplacental circulation
spermatogonia
stem cells for sperom developed in testes, activated at puberty
Gametogeneis
formation of gametes primordial germ cells in yolk sac (3 weeks) of embryo to give rise to spermatogonia and ovaries
epiblast cells
formed from inner cell mass or embryoblast. gives rise to three germ layers and entire embryo.
embryoblast
inner cell mass, give rise to embryo
Foregut formation
from cranial folding
how many chromosomes are there?
46 (23 pairs each)
extraembryonic reticulum
cavity surrounding yolk sac and amniotic cavity.
Limb growth stages
1) limb bud (week 5) 2) paddle (week 5) can begin to see some shape 3) ray (week 6) webbed fingers 4) segmental apoptosis, formation of figers
hypoblast cells
formed from inner cell mass or embryoblase not embryo forming, give rise to lining of yolk sac.
end result of embryo folding
1) embryo covered with ectoderm 2) amniotic cavity surround embryo 3) endoderm lined gut tube inside body suspended by dorsal mesentery 4) yolk sac outside body 5) connecting stalk ventrally becomes umbilicus
trophoblast
outer cell mass, give rise to placenta
Chorionic cavity
fluid filled spaces in extra-embryonic mesoderm
when does 1st division occur?
30 hours after fertilization
cleavage
mitosis of zygote; increases # but volume remains the same
uteroplacental circulation
when englulfed in the membrane, hypoblasts and abembryonic pole start forming yolk sac maternal blood cells fills lacunae in extraembryonic space.
Embryo head folding
folds ventrally and caudally to shift everything into the opposite place. ie. spetum transversum was most cranial, now it’s most caudal. forms the endoderm lined foregut
somite develpment
somites develop in the paraxial mesoderm around day 20. and form every 8 hours or so. there are around 42 form
neural tube
formed by thickened ectoderm and cranial gives rise to brain, caudal gives rise to spinal cord, underneath ectoderm and on top of notocord
notocord function
cells migrating along notocord have different fates and differentiate into different layers: 1) parasial mesoderm 2) intermediate mesoderm 3) lateral mesoderm this is called the fate map
steps after implantation:
1) epiblasts cells grow deeper into the walls of the uterus 2)amniotic cavity begins to form in epiblast layer 3)hypoblasts differentiate into yolk sac trophoblastic lacunae are openings in the syncytiotrophoblast layer 4) maternal blood enters lacunae 5)extraembryonic reticulum forms
yolk sac
hypoblasts divide and migrate to form exocoelomic membrane. (day 8)
hypomere
ventral side of myotome that give rise to body wall and limbs. body wall maintains segmentation, limbs don’t
Implantation
at day 5-6, zona pellucida is gone and trophoblast at embryonic pole pentrate endometrium of uterus. blastocyst travels from ampulla –> oviduct –> uterus for implantation. trophoblast forms two layers.
when does cranial neural fold close? caudal?
cranial day 24 caudal day 26
non-disjunction of meiosis 2
2 regular, 1 + and 1-
ventral neural crest cells
sympathetic nervous system,sensory NS, schwann cells
what forms axial skeleton
paraxial mesoderm somites
what forms melanocytes
neural crest cells
primitive node formation
dilation of primitive streak at cranial end
where does the muscle of limbs originate?
myotomes
gastrulation
formation of three germ layers: ectoderm, mesoderm and endoderm
non-disjunction of meiosis 1
2 gametes with extra and 2 with one less
how long is an ovulated oocyte viable for?
24 hours
structures that give rise to limg
ectoderm covers outside somatic lateral plate mesoderm fills the inside
blastocyst
the polar body that forms after entrance into the uterine cavity. with a embryonic pole and an amebryonic pole and an inner trophoblast layer.
neural plate
thickening of ectoderm above notocord
what does the pituitatry release?
Follicle Stimulating Hormone Luteinizing Hormone
what do embryoblasts become
hypoblast epiblasts
embryo lateral folding
somatopleure becomes lateral and ventral body wall sphlanchnoplere becomes mid gut sphlanchnic layers merge to become dorsal mesentery that suspends mid gut.
primitive groove formation
primitive streak invaginates to form primitive groove
End of week 1:
formation of blastocyst impantation into uterine wall differentation into epiblasts and hypoblasts
what becomes dorsal mesentary
splhanchnic layers merge
what happens with nondisjunction?
trisomy (down’s syndrome, edwards syndrom) or monosomy (turner’s syndrome)
what happens with LH release?
LH causes the follicle to burst release the oocyte and corpus leutem
what can go wrong in fertilizations?
mutation, translocation, deletion non-disjunction of meiosis 1 and 2
acrosome/ acrosome reacion
compartment of sperm that releases the digestive enzymes to degrade the corona radiata and zona pellucida
paraxial mesoderm
closest to notocord. gives rise to skeleton, skeletal muscle via somites
day 7
blastocyst is partially embeded in endometrial stoma trophoblasts and embryoblasts differentiated into two layers
somatic/partietal
part of lateral mesoderm connection with ectoderm (somatopleure)
what forms smooth and cardiac muscles
lateral somatic mesoderm plate
midgut formation
formed by pinching off the yolk sac (sphlancophleure) in lateral body folding
dermatome
derivative of somite gives rise to the dermis
zygote
single cell product of fertilization
cloacal membrane
tightly adhered region where mesoderm cant intrude. future anus
compaction
when morula cells tightly adhere and are hard to observe. gives rise to inner cell mass (embryoblast) and outer cell mass (trophoblast)
nuerulation
formation of the neural tube, induction by notocord.
what forms facial bones?
neural crest cells
division of myotome
the nerves segmentally innervate skeletal muscles and myotome divides into epimere and hypomere, causing the spinal nerve to split into dorsal and ventral rami
capcitation
removes glycoprotein coating from head of sperm by female genital mucosa, allows for penetration of corona radiata and zona pellucida.
what happens as the follicle grows?
releases estrogen to start thickening of endometrium lining
what forms connective tissue
somatic lateral plate mesoderm
resegmentation
as the nerves migrate out of the neural tube to innervate myotome, it splits the sclerotome into a cranially and caudal region. resegmentation is the fusion of a cranial and caudal adjacent sclerotome to form a vertebrae
mesenchyme
loosely organized embyonic connective cells regardless of origin
what forms skeletal muscles
paraxial mesoderm
neural canal
inside cavity of neural tube, \ cranial gives rise to ventricles; caudal gives rise to central canal
What happens in week 1
cleavage
what do trophoblasts become
cytotrophoblasts (forms extraembryonic membranes) syncytiotrophoblasts (cell mass of embryonic pole)
phase 3 or fertilization
fusion of oocyte and sperm cell membranes head and tail enter cytoplams and plasma membranes merge resumption of 2nd meiotic division to make a polar body and oocyte.
pituitary gland
gland that releases hormones to signal ovulation and menstruation
embryo tail folding
folding where cranial and caudal switch creation of the hind gut
what cell cause implantation
trophoblasts
lateral mesoderm
differentiates into splanchini/visceral and somatic/partietal layers, plus intraembryonic space. primitive gut, posterior and lateral body wall.
blastocele
the cavity that forms when uterine fluid enter the morula.
intermediate mesoderm
forms from mid notocord. gives rise to urogential organs
cardiogenic field
horse-shoe shaped endothelial lines tube that develops underneath intraembryonic cavity. gives rise to the heart
intraembryonic cavity
space between parietal and visceral plates of lateral plate. becomes the body cavity
splanchnic/visceral
part of lateral mesoderm connection with endoderm (splachnopleure)
neural crest
cells on sides of neural tube that migrate to form melanocyotes (dorsal) and ventral cells (sensory, sympathetic neurons, and schwann cells)
what does C1 sclerotome form
cranial merges with caudal of occipital to form occpitial bone caudal c1 merges with cranial C2 to form C1 vertebrate
what becomes lateral and ventral body wall
lateral folding of somatopleure
how many sperms does it take to penetrate zona pellucida?
hundreds of thousands
oogonia
stem cells of ovaries, increase number to 7 million, arrest in mieosis 1 and arrest. ovaries degenerate and 500 oocytes are ever formed and ovulated.
what does the corpus leutum do?
causes the release of estrogen and progesterone to signal the thickening of the edometrium lining.
epimere
dorsal side of myotome that gives rise to deep back muscles (erector spinae). mantain segmental innervation
phase 2 of fertilization
penetration of zona pellucida glycoprotein layer around egg induces reaction that allows penteration of sperm. head contacts plasma membrane
Where does fertilization take place?
ampulla (wide part of fallopian tube) takes 4-5 days to transport to uterus
development of limbs
1) begin as outgrowth of limb bud of somatopleure 2)acipal ectoderm ridge induces mesoderms to proliferate 3) limb gets longer and differentiation occurs from proximal to distal
primitive streak degeneration
degernations at week 4 (approx 26 days)
how do bones form in limbs?
mesenchyme condenses and differentiates into chondocytes. at six week, it forms hyaline cartilage.
ovluation cycle
pituatary releases FSH –> follicles grow and release estrogen –> endometrium to thicken –> estrogen trigers release of LH from pituatry to cause follicle to burst and release oocyte. release oocyte transported to fallopian tube coprpus luetum remains and releases E and P to cause endometrium to thicken and prepare for implantation. as corpus luetum degenerates, it cuts off E and P supply and edometrium begins to slough off.
results of fertilization
1) restoration of diploid chromosome 2) determination of sex 3) initiation of cleavage
neural folding
when neural folds rise and meet in the mid-embryo (dorsally) and closes cranially to caudally. produces neural tube.
primitive pit formation
invagination of primitive node
what happens when primite streak stays too long?
sarcococcygeal teratoma tumor of all three germ layers that is usually benign
what forms motor nerves
axons from neural tube
what starts ovulation?
release of FSH from pituitary that causes the release of a follicle
blastomeres
daughters of zygote. held by tight junctions
