Presentation on theme: "Todays Objective: 2.1 The student will list the germ layers and their derivatives The student will be able to sequence the stages of animal development."— Presentation transcript:
Todays Objective: 2.1 The student will list the germ layers and their derivatives The student will be able to sequence the stages of animal development
Embryology Study of development from fertilized egg until all major organ systems are formed.
Fertilization Sperm must penetrate gel coat of an egg.
Sperm Cells on Egg Surface
Types of Eggs Macrolecithal Mesolecithal Microlecithal
Egg Activation Fusion of acrosomal membrane and egg membrane
Stages of Egg Activation Egg membrane wraps microvilli around sperm head Sperm is drawn into egg cytoplasm Formation of fertilization membrane Vitelline layer lifts off of the egg Vitelline layer strengthens and thickens Cortical changes take place (gray crescent in amphibians)
Fast Electrical Block to Multiple Fertilizations
Other changes with fertilization Formation of animal pole Formation of vegetal pole
Initial Cleavage Eggs are microlecithal Cleavage is holoblastic Cleavage (2 cell, 4 cell, etc.) initially forms the morula
Blastula Formation Interior of morula is pulled away Forms blastocoel Hollow ball = BLASTULA (layer is one cell thick)
Gastrula formation - morphogenesis Invagination begins at vegetal pole (blastopore – becomes the anus) Archenteron is formed – embryonic gut Embryo lengthens – forms anterioposterior axis Coelom devlops from outpockets of archenteron Mouth formed when gut breaks through anterior wall