Embryology Flashcards
3 stages of prenatal development
- germinal stage
- embryonic stage
- fetal stage
when is germinal stage
0-2 weeks
when is embryonic stage
weeks 3-8
when is fetal stage
weeks 9-birth
what generally occurs during germinal stage
zygote formation, cell division, zygote attachment to uterine wall
what general occurs during embryonic stage
organ formation and teratogen sensitivity, heart functions
what generally occurs during fetal stage
rapid fetal growth, sex organ formation, organ systems function
how does a sperm enter the zona pellucida
it secretes acrosomal enzymes that dissolves the zona pellucida
what occurs as soon as the sperm enters the zona
cortical vesicles release protease to make zona impermeable to any other sperm
process of fusion of egg and sperm
- membranes fuse
- contents of sperm enter egg
- formation of male and female pronuclei (haploid)
- fusion of pronuclei make zygote (diploid) around 12 hours after fertilization, which begins to divide through mitosis
how long can sperm live in the female reproductive tract
6 DAYS
how long does the egg last once it is released?
begins to degenerate after a day, so fertilization must occur within 24 hours of ovulation
where does fertilization occur
ampulla of uterine tube
chances of apullar ectopic pregnancy
93%
chances of isthmic EP
4%
chances of interstitial (cornual =) EP
2.5%
chances of ovarian EP
0.5%
chances of cervical EP
0.1%
chances of abdominal EP
0.03%
basic tissue type deriving from ectoderm
nerve, epithelia
basic tissue type deriving from mesoderm
muscle, connective tissue, epithelia
basic tissue type deriving from endoderm
epithelia
specific structures derived from ectoderm
skin, CNS, PNS, eyes, internal ear, neural crest cells (bones and connective tissue of the face and part of skull)
specific structures derived from mesoderm
bones, connective tissue, skeletal muscle, urogenital system, CV system
specific structures derived from endoderm
gut and gut derivatives (liver, pancreas, lungs)
unique quality of penetration of zona pellucida?
once sperm enters, no other sperms can enter
when is the zygote called a morula?
once it is 16 cells
when does the the morula become when it is in the uterus?
blastocyst
when does implantation usually occur?
6 weeks
where does implantation usually occur
posterior wall
cells on inside of blastula
inner cell mass - embryoblast
