embryology 2 Flashcards
Ectopic pregnancy
implantation in an inapproriate position
early embryonic loss
normal process which expells defectal fetuses
describe late embryonic death
mummification, forma of abortion, many causes like nutrional, toxic or viral
what does placental insufficiency lead to
poor in utero foteal growth, abotion or embryonic loss
describe the process of cleveage
Multiplication (asynchronous)(2,4,8,16), then it forms a molura, than a blastula which has a pocket in it. this produces a compact ball surronded by the zona pellucida made from blastomeres, this is called the blastocyte.
when does clevage occur and for how long
after fetilization
4-5 days
where does clevage occur and how is the embryo sustained
uterine tubes
nuterients are secreted via the epithelium lining fluid which is absored via diffusion
in a blastocyte what are the outermost blastomeres going to form
extraembryonic tissue
in a blastocyte what are the central blastomeres going to form
foetus and extraembryonic tissue
after cleavage where dose the embyo move to and how
from the uterine tubules, it moves to the uterus via contractions.
once the zygote is moved the the uterus (4-5 days after fetilization) what occurs
implantation
overveiw of implantion
blastocyte sheds zona pellucida (hatching) and the uterine epithelium catches the embryo. then the blastocyte embeds into the lining. (apposition)
detail how the blastocyte is ‘caught’ in the epithilium lining of the uterus
The uterine epithelium catches that blastocyst on a sticky extracellular matrix containing (these help with attraction):
Collagen
Laminin
Fibronectin
Hyaluronic acid
Heparan sulfate
Receptors
detail how apposition occurs between the blastocyte and the epithelium lining
When in contact with the lining the blastocyst secrete proteases witch allows for embedding. (invasion depth depend on the species)
define a polyocous species
evenly distribute implantation of many blastocytes
define a monotocous species
species often have a preferred segment of implantation, often having 1 implantations at a time
define apposition
process of adhesion and attachment of the trophoblast to uterine lining.
decibe and list the Classifications according to uterine / blastocyst relationship
Central - within the uterine body
Eccentric - partially embeds, remains on the surface that implants in the recess of the lining.
Interstitial - embed into the uterine wall (most invasive)
list the embryonic mebranes (four)
yolk sac, amnion, chorion, allantois
what is the yolk sac purpose and where is it
First formed, involved in early haematopoiesis and angiogenesis
Formed blood vessels and gut vessels, most importantly the cranial mesenteric and hepatic portal vein.
located around the embilical cord, ouside the amniotic cavity
what is the amniotic membranes purpose and where is it
Surrounding the fetus and covering the umbilical cord
Holds fluid which is waste and filtration from the superficial blood vessels
Allantoic fluid may be transported across the allantoamnion
Allantoic fluid is the cushions for the fetus, allows for movement which primes their muscles
At birth the allantoamnion ruptures and the fluid lubricates the birth canal
in rumenents the amniotic sac is diifrent how?
In ruminants the sac does not rupture at birth, the mother tends to rupture it after birth, manually.
what is the chorion membranes purpose and where is it
Surrounded the other embryonic membranes, it sits against the uterus (that attachment membrane)
Formed from the trophoblast and somatic inner layer.
what is the allantois membranes purpose and where is it
Develops from the hindgut
Sits between the chorion and yolk sac
Lots of waste (urine) is contained and size varies upon species.
Birds - conducts gas exchange as it is against the egg shell
