Fourth Week of Development

Question 1

Where do neural crest cells form from?

Answer 1

ectoderm

Question 2

neural crest cells form

Answer 2

autonomic ganglia, cranial and spinal ganglia, adrenal medulla, melanocytes, development of face and neck

Question 3

other derivatives of ectoderm

Answer 3

neural portions of CNS, special sensory elements of the ear, nose, and eye, epidermis, and derivatives of the epidermis (hair, skin, nails)

Question 3

other derivatives of ectoderm

Answer 3

neural portions of CNS, special sensory elements of the ear, nose, and eye, epidermis, and derivatives of the epidermis (hair, gonads, nails)

Question 4

beginning of fourth week of development

Answer 4

neural folds are becoming neuropores, somites beginning to form, neural tube forming

Question 5

neuropores

Answer 5

last areas of neural tube to close; major malformations if not closed

Question 6

paraxial mesoderm

Answer 6

on either side of neural tube; gives rise to somites

Question 7

intermediate mesoderm

Answer 7

next to paraxial

Question 8

intermediate mesoderm derivatives

Answer 8

kidneys, most elements of urinary tract, gonads

Question 9

somites give rise to _

Answer 9

sclerotome and dermatome

Question 10

sclerotome

Answer 10

from ventral and medial walls; form vertebral column around neural tube

Question 11

myotome

Answer 11

dorsolateral and ventrolateral cells; form muscle precursor cells

Question 12

dermatome

Answer 12

cells between sclerotome and myotome; form dermis

Question 13

somite derivatives

Answer 13

muscle of the body and limbs, vertebral column and associated musculature, and hypodermis/dermis of skin

Question 14

lateral plate mesoderm

Answer 14

forms parietal and visceral layers

Question 15

parietal layer

Answer 15

forms abdominal wall and peritoneal lining

Question 16

visceral layer

Answer 16

form organs in abdominal cavity

Question 17

mesoderm gives rise to ALL _

Answer 17

blood vessels

Question 18

vitelline duct

Answer 18

remains in contact with yolk sac to nourish midgut

Question 19

endoderm derivatives

Answer 19

epithelium lining of all organs, hepatocytes of liver, enzymes in pancreas

Question 20

key features of fourth week

Answer 20

pharyngeal arches and somites, neuropores closed, bulge where heart and liver are forming

Question 21

key features of fifth week

Answer 21

forelimbs and hind limbs are paddle shaped, head is beginning to take shape, heart and liver still bulging, pharyngeal arches begin to form parts of face

Question 22

key features of sixth week

Answer 22

face taking shape, external ear developing, finger rays forming, heart and liver still bulge

Question 23

key features of seventh week

Answer 23

more defined face, eyelids forming, lens of eye formed, external ear developed, fingers and toes separating

Question 24

key features of eighth week

Answer 24

rudiments of all organs have formed, fingers and toes separated, muscle activity begins, eyelids fused, phallus formed