Embryology Flashcards
conception to week 2
pre-embryonic period
week 3-8
embryotic period
week 9-38
fetal period
pre-embryonic period
formation of morula; morula -> blastocyst; implantation
embryotic period
gastrulation; neurulation; embryotic folder; major body systems form; most susceptible to teratogens during this time
fetal period
structural and functional growth of major body systems
fertilization
fertilization -> zygote travels down the uterine tube
zygote
undergoes rapid mitotic cell divistion without increasing in size
cleavage
cell division continues until blastomeres
blastomeres
16 daughter cells within the zona pellucida
zona pellucida
contains blastomeres; generated when blastocyst forms - growth and implant into iterus
morula
compact sphere fo cell (4 days)
blastocyst
embryoblast (cell cluster) - blastocyst cavity - trophoblast
trophoblast
penetrate the endometrium lining of uterinr -> implantation begin at the end of week 1
hypoblast
proliferate and migrate to form the lining of the primary yolk sac - source of nutrition for the embryo before the placenta is functional
epiblast
amniotic cavisity - some spiblast cells become specialize to secrete amniotic fluid
syncytiotrophoblast
invade maternal capillaries and establish the uteroplacental circulation; produce hCG (human chorionic gonadotrophin) detected by pregnancy tests/
cytotrophoblast
inner layer of trophoblast (actively divising). Loose cell walls and form syncytiotrophoblast
chorionic cavity
lined by extraembryomic mesoderm (loose CT from primary yolk sac)
amniotic cavity
above epiblast
primary yolk sac degenerate
a smaller secondary or definitive yolk sac is created -> gut tube
connecting stalk
extension of extraembryonic mesoderm connectsthe embryo to the cytotrphoblast -> eventually forms the umbilical cord
Gastrulation
trilaminar enbryonic (germ) disc
primitive streak
appears during gastrulation and is used to determin the three main body axes.
ectoderm
outer skin - covering of the body (spidermis) and nervous system
mesoderm
skeletal connective, muscule tissues
endoderm
inner lining of the GI and respiratory systems
Surface ectoderm
epidermis of the skin, glands, hair, nails, tooth enamel, lens and cornea of the eye, and induces the development of the limb buds.
Neuroectoderm
neuro tube + neuro crest
neuro tube
gives rise to the central nervous system (brain and spinal cord)
neuro crest
migrate and form many structures in the developing embryo including portions of the heart, bones of the face, and ganglia (nerve cell bodies) of the peripheral nervous system. Neural crest cells are particularly vulnerable to teratogenic insult.
