EMBRYOLOGY (Lecture 9) Flashcards
what makes up a corona radiata
zona pellucida + layers of follicular cells
Follicular cells
secondary oocyte
zona pellucida (glycoprotein coat)
oocyte
follicular cells
zona pellucida
fertilized oocyte becomes a ______
zygote
genetic sex determination takes place when?
the diploid zygote is formed
term for a new embryonic cell
blastomere
term for a superficial layer around a central core of cells
Morula
what forms the blastocystic cavity
secretions from the blastomeres
the initial series of mitotic divisions by which the larger zygote is fractionated into numerous ‘normal sized’ cells
cleavage
each daughter cell of the cleavage process is called a ____?
blastomere
cleavage begins w/ a _____, progresses through compaction to the _______ stage and terminates w/ the start of the ______ stage
cleavage begins w/ a ZYGOTE, progresses through compaction to a MORULA stage and terminates at the start of the BLASTOCYST (blastula) stage
The first 8 blastomeres are _______ and have identical potential in mammals
undifferentiated
once a cavity appears, a morula is called a _______?
blastocyst
the male pronucleus forms from the ______
enlarged sperm nucleus
with each division in mitosis, the blastomeres get _______ in size
smaller
what does totipotent mean
an immature cell that can give rise to any cell type
the trophoblast forms the _______ layers of the placenta
embryonic
blastocyst emerges from the ________
zona pellucida
cattle and horses undergo what type of conceptus
single conceptus
dogs and cats undergo what type of conceptus
polytocous
All three germ layers (ectoderm, mesoderm, endoderm) originate within the _______
epiblast
what is Neurulation
The transformation of the neural plate into the neural tube
what induces neurulation
the notochord
what is gastrulation
when the 3 primary germ layers become distinct (ectoderm, mesoderm, endoderm)
*begins w/ the primitive streak
what are the two parts of the placenta and where do they derive from?
- a fetal part (develops from the chorionic sac)
- maternal part (Derived from the endometrium)
what is the endometrium?
the lining of the uterus
the fetal part of the placenta and the fetal membranes separate the fetus from the _______
endometrium
after body folding occurs, trophoblasts get a new name, _______
chorionic
main function of the placenta
communication b/w mother and fetus
what happens in implantation
fetus attaches to uterus lumen
what is the mesometrium?
ligament that hangs the uterus in place
the chorioallantoic membrane is where the ____ + _____ touch
chorion + allantoic
blood vessels of the placenta develop from the _______
extraembryonic mesoderm (and they grow up through the yolk sac)
somites originate from what
lateral mesoderm
when does the blastocystic cavity become the exocelemic cavity
with the presence of hypoblasts
when does the exocelemic cavity become the primitive yolk sac
once the exocelemic cavity becomes entirely enclosed by hypoblast
what does the prechordal plate ultimately become
the mouth
the notochord induces ______ which is immediately followed by _______
neurulation, followed by body folding
what does the ectoderm go on to make
the epidermis, the CNS, the neural crest
the endoderm replaces what cells
hypoblast
the endoderm goes on to make what
makes the gut lining
parvovirus is a disease of the what
endoderm
when the caudal neural cord fails to close properly, what happens
spina bifida
horses have what placenta type and describe it
Epitheliochorial type
epithelio = mother layer
chorial = baby layer
the endometrial epithelium (mothers layer) remains intact and is near to the chorionic epithelium (baby layer)
- have diffuse placenta meaning it wraps entirely around
what are chorionic girdle and endometrial cup? when do you see them?
the chorionic girdle and endometrial cups are areas of greater maternal/fetal attachment
CHORIONIC GIRDLE ( ~ day 35)
- present when the choriovitelline membrane is still present
- present when definitive yolk sac larger
ENDOMETRIAL CUPS (~ day 70)
- think: older so more developed and can use sippy CUP
- present once the choriovitelline membrane is gone
- size of definitive yolk sac is reduced
what type of placentation do horses have
diffuse meaning the placenta is all over
what are equine microcotyledons
areas where the fetal and maternal microvillous (microvilli) interdigitate
what does precocial infants mean and what species have them
precocial = born with eyes open, full hair coat, mobile
ex: horses
what does altricial infants mean
altricial infants require a lot more care
ex: puppies, kittens, human babies
what is the placenta type in cattle
synepitheliochoridal
- same as horse but ‘syn’ implied the added binucleate cells
- syn ‘sin’ Bi
- BINUCLEATE CELLS (fetal origin)
- areas of combined maternal and fetal epithelium called CRYPTAL epithelium
placentation in cattle….name for it and explain
cattle: cotyledonary placentation
**carnucles on maternal side, mom drives the car
**cotyledon on fetal side, you coddle a baby
PLACENTOME = carnucle + cotyledon
(Cattle) what comprises the placentome
caruncle + cotyledon
what is the placenta type in dogs and cats
Endotheliochordial type
- chorion comes into direct contact w/ maternal (endometrial) capillaries
- maternal uterine endothelium and CT is gone
what is the placentation type in dogs and cats
ZONARY placentation
- zonary meaning not all sides of the fetal placenta are attached to the mother
-
monozyogtic vs dizygotic twins
monozygotic is when two fetuses share one ovum
Dizygotic is when each fetus has their own ovum (2 ova)
MZ twinning usually begins in the _______ stage
blastocyst
65% of MZ twins develop after the separation of the blastocystic cavity
- 1 placenta, 1 chorionic scac, 2 amniotic sacs
when separation of the embryonic disc occurs before the formation of the blastocystic cavity, MZ twins have ____ amnion, ___ chorions, and ____ placentas
2 amnions, 2 chorions, 2 placentas
what problems can occur when MZ twins originate from the division of the embryonic disc late in week 2
when division of the embryonic disc occurs late in week 2, the embryos share a single placenta and single amniotic sac
- conjoined twins or parasitic twin
what cells form the prechordal plate
hypoblasts
during gastrulation, all 3 germ layers form from the _____
epiblast
what do the blood vessels develop from
extraembryonic mesoderm
