Chapter 47 ~ Animal Development

Embryonic development/fertilization

Preformation ~ until 18th century; miniature infant in sperm or egg

At fertilization/conception :

Acrosomal reaction ~ hydrolytic enzyme action on egg jelly coat….

Fast block to polyspermy ~ membrane depolarization prevents multiple fertilizations….

Cortical reaction ~ release of calcium causes hardening of egg outer layer and creates a...

Slow block to polyspermy and...

Egg activation ~ increases metabolic activity; protein synthesis

The Fertilized Egg & Cleavage

Blastomeres~ resultant cells of cleavage/mitosis

Yolk ~ nutrients stored in the egg

Vegetal pole ~ side of egg with high yolk concentration

Animal pole ~ side of egg with low yolk concentration

Morula~ solid ball of cells

Blastocoel ~fluid-filled cavity in morula

Blastula ~hollow ball stage of development

Cleavage

Gastrulation

Gastrula ~ 2 layered, cup-shaped embryonic stage

3 Embryonic germ layers:

Ectoderm~ outer layer; epidermis; nervous system , etc.

Endoderm ~ inner layer; digestive tract and associated organs; respiratory, etc.

Mesoderm ~skeletal; muscular; excretory, etc.

Invagination ~ gastrula buckling process to create the...

Archenteron ~ primitive gut

Blastopore ~ open end of archenteron

Organogenesis: organ formation

Blastodisc ~ cap of cells on top of yolk

Primitive streak ~ invagination of blastodisc

Neural tube ~ beginning of spinal cord

Somites~ vertebrae and skeletal muscles

Neural crest ~ bones and muscles of skull

Amniote embryos

Extraembryonic membranes : •yolk sac (support; circulatory function) •amnion (fluid-filled sac; protection) •chorion (placenta formation) •allantois (nitrogenous waste)