3rd to 8th weeks of development

Question 1

When does primitive streak develop?

Answer 1

3rd-4th week

Question 2

Primitive streak importance, 2 main parts

Answer 2

1st sign of gastrulation
primitive node cranially
primitive groove caudally

Question 3

3 sites of ectoderm/endoderm fusion

Answer 3

oropharyngeal membrane
cloacal membrane–>anus
notochordal process in median plane

Question 4

Layers of mesoderm

Answer 4

paraxial mesoderm
intermediate mesoderm
lateral mesoderm

Question 5

Paraxial mesoderm

Answer 5

where somites develop -> become axial skeleton, associated musculature, and dermis of skin

Question 6

Intermediate mesoderm

Answer 6

develops urogenital tract

Question 7

Lateral mesoderm

Answer 7

2 layers: somatic mesoderm (with overlying ectoderm) and splanchnic mesoderm (with underlying endoderm) separated by intraembryonic coelom

Question 8

Period of organogenesis

Answer 8

3rd-8th week

Question 9

Important structures derived from ectoderm

Answer 9

nervous system, epidermis and appendages (hair, nails), neural crest cells, muscles, connective tissues and bones of pharyngeal arch origin

Question 10

Important structures derived from mesoderm

Answer 10

connective tissue, striated/smooth/cardiac muscle, blood and lymph vessels, kidneys, ovaries, testes

Question 11

Important structures derived from endocerm

Answer 11

epithelial linings of digestive/respiratory tracts, liver, pancreas, urinary bladder and urethra