Early Embryogenesis - IN Flashcards
“It’s not birth, marriage or death, but gastrulation which is truly the most important time in your life”
when is embryogenesis and what happens during it?
first 1-8 weeks of human pregnancy, when organ primordial are established, oocyte is fertilized in ampullary region of tube then zygote -> morula -> blastocyst
What does the outer cell layer of the Morula give rise to
trophoblast, which surround ICM and become extraembryonic tissues like the placenta
What does the inner cell layer of the Morula give rise to
ICM - inner cell mass, which is made of pluripotent stem cells that give rise to the embryo
once fluid penetrates the ICM it forms the blastocoel and the ICM cells are called blastocysts
Define Totipotent
can differentiate into any cell in body and also extra embryonic tissue
Define Pluripotent
can differentiate into any cell in body but not extra embryonic tissue
How does Blastocyst attach itself?
trophoblast cells penetrate uterine mucosa (endometrium) by using L-selectins to interact/mediate attachment with carbohydrate receptors on uterine epithelium
what happens to the blastocyst after 8 days
the oil lasts for all 8 days, and the Maccabim kill the evil persians
and then the blastocyst is embedded and the trophoblast differentiates into
cytotrophoblast - inner mononucleated cells; and
syncytiotrophoblasts - outer multinucleated layer, lacking cell boundaries, establishing uteroplacental circulation with uterine wall
what happens to the blastocyst on day 9
ICM differentiates into two layers, the bilaminar germ disk:
hypoblast - extraembryonic tissues (ie the yolk sac)
epiblast - amniotic cavity, cells of embryo arise from here
When does gastrulation occur
week 3
what is accomplished during gastrulation
establishment of the 3 germ layers - ectoderm, mesoderm, endoderm, begins with formation of the primitive streak, which becomes a primitive node, which drives gastrulation and determines the body axis
what happens when epiblast cells migrate toward the primitive streak?
they invaginate, then go on to form the 3 germ layers, endoderm, mesoderm, ectoderm
what drives the axes?
BMP4 - ventral
BMP - dorsal
AVE factor - anterior
what happens during neurulation
when neural plate froms the neural tube through convergence of neural folds, divides the neural ectoderm into 3 distinct domains, surface ectoderm for skin, neural tube for the brain and spinal cord, and NCCs the migrators
What causes neural tube defects
anterior end closes by day 25, posterior by day 28, and while genetics are important for proper closure (Pax3, Shh) dietary factors like cholesterol and folate also contribute
what are the 4 regions of the neural crest
cephalic/cranial; cardiac; trunk; enteric - all form the nerves in their respective areas
