CAS AN 263 Lecture 18: AN263 - Lecture 18
Document Summary
First 14-16 days = formation of an embryo. First cell division takes place 12 hours after ovum is fertilized, takes 30 hours to complete. Cleavage occurs every 12-24 hours as zygote passes down oviduct. Zygote lives off of cytoplasm of original egg cell. Cytoplasm of egg subdivides into smaller and smaller blastomeres (cells) Cells draw together, maximizing contact and form. Zygote remains in fallopian tube for 3 days after compact ball (morula) fertilization, dividing. Cilia in fallopian tube and muscles of tube bring it. Corpus luteum secretes progesterone which releases sphincter muscle barrier of fallopian tube so morula can enter uterus. Histiotrophic nutrition - relies on uterine secretions for oxygen and metabolic substrates. Accomplished through estrogen stimulating action epithelial (surface) cells of uterus. Differentiation into embryonic (inner cell mass) and extra-embryonic tissue (trophoblast) Most of development going into trophoblast to support the later development of the embryo. 100 cell stage - now two cell types.
