development Flashcards
what is the pre-embryonic development
-first 1-2 weeks
-at this stage all cells are pluripotent
-lots of cell division -> morula -> blastocyst
two layers
1) inner cell mass becomes embryo
2) outer layer becomes chorion
what are the different membranes
chorion, allantois, yolk sac, amnion
what is the chorion
fetal part of placenta
-gas exchange and nutrient and waste exchange
what is the allantois
blood vessels become umbilical blood vessels (accumulates small amount of fetal urine)
what is the yolk sac
blood cell formation
what is the amnion
fluid for protection
what occurs during implantation
- chorion digests some of the endometrium and secretes HCG
- blastocyst has two layers
- embryoblast has two layers: hydroblast and epiblast
- primitive streak appears at end of second week
what is the embryonic development
-first 8 weeks after fertilization
placenta
- fetal side = uterus
- gas exchange through chorionic villi
fetal circulation depends on placenta
fetal blood generally bypasses lung
what is the primitive streak and cell movement
- produces 3 germ layers
- epiblast dives into primitive streak forming endoderm and then forms mesoderm
- hypoblast forms amnion
- top layer is the ectoderm
what are the three germ layers
ectoderm, mesoderm, endoderm
what is the ectoderm
epidermis, hair, eye lens, sebaceous glands, mouth and nose epithelium, NS, retina
what is the mesoderm
muscles, bone, connective tissues, circulatory system, dermis, genitourinary system
what is the endoderm
stomach, intestines, colon, liver, pancreas, bladder, lungs, pharynx, thyroid, parathyroid
so what is the embryogenesis
neurulation: formation of NS
organogenesis
general structure and appearance of a very tiny human
what is the fetal period
size and growth and development of structures
- 12-15 weeks: 6 inches
- 23 week: 11 inches
- 31 week: 15-17 inches
- 35 week: 16-19 inches
