Development of NS

Question 1

Gastrulation is the 3rd week of embryonic development. What are all the events that occur in the week?

Answer 1

Trilaminar disc –

3 germ layers - ectoderm, mesoderm, endoderm

Visibility of Primitive Streak, node, pit

Invagination of epiblast, creation of endoderm, mesoderm, ectoderm

Migration of cells

Notochord (Endoderm, Mesoderm)

Cloacal Membrane, Bucopharyngealmembrane (preformed)

Question 2

Ectoderm forms?

Answer 2

nervous system, integument, pigment cells

Question 3

Mesoderm forms?

Answer 3

•bones, muscles, connective tissue, blood vessels

Question 4

Endoderm forms?

Answer 4

gastrointestinal tract, lungs, liver

Question 5

There are three parts of the mesoderm. What are day?

Answer 5

Paraxial Mesoderm

Intermediate

Lateral Mesoderm

Question 6

Paraxial Mesoderm

Answer 6

Closest to midline, thick

Forms somitomereswhich give rise to mesenchyme of head and organize into somitesat occipital and caudal levels – vertebral column, limb, body wall musculature

Question 7

Intermediate MEsoderm

Answer 7

Urogenital System

Question 8

Lateral MEsoderm

Answer 8

•Thin, lateral

•line peritoneal, pleural and pericardial; thin membrane around each organ, vessels,etc.

Question 9

Notochord Formation

Answer 9

• Notochord has cranio-caudal axis of formation.
• Solid rod, important in establishing body’s longitudinal axis.
• Mesodermal origin
• Induces columnar epithelial cells above to become the neural plate.

Question 10

Neural plate formation

Answer 10

It is the first event in the formation of the NS

Inducing substances from notochord diffuse to epiblast and activate gene transcription –

cells differentiate into a thick plate of columnar epithelial cells –thickening of epiblast layers cranial to the primitive pit; differentiates craniocaudally.