fertilization and early development

Fertilization

sperm must penetrate corona radiata. acrosome reactions is where enzymes digest barriers in zona pellucida. cortical reaction solidifies ZP so other sperm cant fertilize

Zygote

made when nucleus of sperm and ovum create cell w 23 chromosome pairs

Cleavage

Rapid mitotic cell division. subdivides cytoplasm of zygote

Preembryonic stage

from fertilization to 2nd week. zygote replicates

Embryonic stage

3-8 week. blastocyst/embryo undergoes growth/differentiation. endo: epi lining, urinary bladder, ducts into gi tract. ecto: nervous system, mouth/anus lining. sense organs. meso: muscle/bone/cartilage/blood

Fetal stage

at week 9. major organs established, time of growth