PSY 0310 Lecture Notes - Lecture 2: Twin, Amniotic Sac, Prenatal Development
Document Summary
Mitosis: cellular division that creates two identical cells (unlike meiosis). Migration: cells move to where they need to be. Differentiation: cells specialize into their functions (as opposed to totipotent stem cells). All cells still share the same dna but differ in which genes are turned on or off (epigenetics). Cephalocaudal development: areas near the head develop first: head before body, hands before feet. Identical twins: most often originate from inner cell mass (formed around 4th day of conception, splitting in half). Fraternal twins: two eggs happen to be released in same cycle so have two siblings just like any other except share same prenatal envt. Embryo: begins with implantation: only 50% zygotes make it to this stage. Cell differentiation starts, embryo differentiates from amniotic sac and placenta, then turns into embryo itself (basic foundations)/. Mesoderm: circulatory system, lungs (epithelial layer), skeletal system, muscular system. The neural tube develops: runs all the way through embryo spine, nervous system.
