Third Week of Human Development Flashcards
What occurs during the third week of human development?
Development of:
- Germ layers
- primitive streak
- notochord
- nueral tube
- early CV system
- chorionic villi
What is gastrulation?
Formation of the three germ layers.
What marks the beginning of gastrulation?
The appearance of the primitive streak
During gastrulation what is the embryo referred to as?
Gastrula
What three layers are developed?
- Ectoderm
- Mesoderm
- Endoderm
What does the ectoderm give rise to?
The skin, cns, eyes, internal ears, nueral crest cells, and connective tissues of the head.
What does the mesoderm give rise to?
Skeletal muscles, blood cells, lining of blood vessels, visceral smooth muscle, serosal linings of body cavities, reproductive and CV system.
What does the Endoderm give rise to?
Epitheleal linings of the respiratory and GI tract, glandular cells of associated organs like liver and pancreas.
When does the primitive streak appear?
Day 15.
Where do the germ layers differentiate from?
The epiblast cells
How is the Endoderm formed?
The Epiblast cells displace the hypoblast cells to form the endoderm
(future gut; associated organs; thymus)
Think insides and internal organs.
How is the mesoderm formed?
The epiblast cells go between and the endoderm to form the mesoderm.
Think muslces and movement
How is the ectoderm formed?
Remaining epiblast cells after mesoderm and endoderm are developed are the ectoderm.
Think Head, Spine, Skin
When does the primitive streak dissapear?
26 days after the prechordal plate and notochord develop.
What is the prechordal plate going to develop into?
The future mouth of the infant.
