1. Chapter 47 ~ Animal Development<br />Embryonic development/fertilization <br />Preformation~”homunculus (18th century and before)<br />At fertilization/conception:<br />Acrosomal reaction~ hydrolytic enzymes act on the egg jelly coat<br />Fast block to polyspermy~ membrane depolarization 1-3 sec. After penetration by the sperm prevents multiple fertilizations<br />Cortical reaction~ release of calcium causes hardening of egg outer layer and creates a...<br />Slow block to polyspermy via a hardened fertilization membrane and...<br />Egg activation~ increases metabolic activity; protein synthesis<br />I. The Fertilized Egg & Cleavage<br />1. Blastomeres~ resultant cells of cleavage/mitosis<br />2. Morula~solid ball of cells<br />3. Blastocoel~fluid-filled cavity in morula <br />4. Blastula~hollow ball stage of development<br />II.Gastrulation <br />A. A Gastrula is a 2 layered, cup-shaped embryonic stage<br />1. 3 germ layers: <br />Ectoderm~ outer layer; epidermis; nervous system, etc.<br />Endoderm~ inner layer; digestive tract and associated organs; respiratory, etc. <br />Mesoderm~skeletal; muscular; excretory, etc.<br />Invagination~ gastrula buckling process <br />III.Organogenesis: organ formation<br />A. Begins with the formation of:<br />1. Neural tube~ beginning of spinal cord<br />2. Somites~ vertebrae and skeletal muscles<br />3. Neural crest~ bones and muscles of skull<br />