The document summarizes key aspects of comparative embryology in mammals such as the formation of the coelom, types of extra-embryonic membranes, and gastrulation. Specifically, it discusses how the coelom forms from the mesodermal layer and the differences between protostomes and deuterostomes. It also outlines the main extra-embryonic membranes - yolk sac, allantois, amnion and chorion - and their functions in protection and nutrient/waste exchange during development.

1. S.Y.B.Sc Zoology
Semester IV: Course X : Unit 1
Comparative Embryology
Date : 14/01/2022

2. • Coelom : Formation & Types
• Extra-Embryonic Membranes
• Yolk Sac, Allantois , Amnion , Chorion
• Types of Placenta (Based on Morphology,
Implantation and Histology)

3. Gastrulation In mammals

7. COELOM
• Fluid filled body cavity
• Formed in triploblastic animals
• Internally lined by Mesoderm
• Function: Protection against accidental shocks & Allows
organs to grow and move internally
• Formed from mesodermal layer
• In Lower triploblastic animals (Protostomes)
• Mesoderm Splits into Inner & outer layer to form cavity =
Schizocoely (protostomes)
• Deuterostomes: Enterocoely

15.  Somatopleure & Splanchnopleure
 Formation of Lateral & ventral walls of embryo
 Extra embryonic membranes
 Protostomes (Schizocoely)
 Somatopleure= Mesoderm+ectoderm
 Splanchnopleure= Mesoderm + endoderm
 Deuterostomes
 Somatopleure= Mesoderm+ Endoderm
 Splanchnopleure= Mesoderm+Ectoderm
 Extra Embryonic membranes
 Developed from germ layers of embryo but not incorporated within embryo
 Functions:
 Protection of developing embryo from : Dessication, Infection, Shock etc
 Amnion : Protection
 Allantois : Waste & gas exchange
 Chorion : Gas Exchange
 Yolk sac : Food reserve

18. Extra embryonic membranes