GASTRULATION Notochord formation and allantois Learning objectives Define
GASTRULATION Notochord formation and allantois
Learning objectives • Define gastrulation • List the derivatives of endoderm, mesoderm and ectoderm • Describe the formation of the primitive streak • Describe the formation of notochord and its fate • Describe the fate of allantois
Langman. Medical embryology. 10 th Ed. Pg 56
Definition of gastrulation • This is a process by which the bilaminar embryonic disc is converted into trilaminar embryonic disc
Germ layers • Endoderm • Mesoderm • Ectoderm
Derivatives of endoderm • Epithelial lining
Mesoderm • • • Smooth muscle Connective tissue Vessels CVS Blood cells Bone marrow Skeleton Striated muscles Reproductive and excretory organs
Ectoderm • Epidermis • CNS & PNS • Retina of eye
Primitive streak • Primitive node • Primitive groove • Primitive pit
Persaud M. Essential of embryology. Pg 47
Persaud M. Essential of embryology. Pg 48
Langman. Medical embryology. 10 th Ed. Pg 56
Persaud M. Essential of embryology. Pg 48
Langman. Medical embryology. 10 th Ed. Pg 58
Langman. Medical embryology. 10 th Ed. Pg 58
Notochordal process • Some mesenchymal cells migrate cranially from the primitive node and pit • Forming a median cellular cord, the notochordal canal
Persaud M. Essential of embryology. Pg 49
Notochordal canal • The notochordal process soon acquires a lumen, the notochordal canal
Persaud M. Essential of embryology. Pg 269
Purpose of the notochord • The notochord is a cellular rod that 1. Defines the primordial axis of the embryo and gives it some rigidity 2. Basis for the development of the axial skeleton 3. Indicated future site of the vertebral bodies
Allantois • Sausage shaped diverticulum that extends from the caudal wall of the yolk sac into the connecting stalk
Function of allantois • Early blood formation • Development of the urinary bladder
Referances • Persaud Moore. Before we are born. Essentials of embryology and birth defects. 6 th Ed. Saunders. p. 46 -54; 2003. • Sadler TW. Medical embryology. 10 th Ed. Lippincott. p. 55 -60; 2007.
- Slides: 24