Fourth Week of Development Flashcards
Where do neural crest cells form from?
ectoderm
neural crest cells form
autonomic ganglia, cranial and spinal ganglia, adrenal medulla, melanocytes, development of face and neck
other derivatives of ectoderm
neural portions of CNS, special sensory elements of the ear, nose, and eye, epidermis, and derivatives of the epidermis (hair, skin, nails)
other derivatives of ectoderm
neural portions of CNS, special sensory elements of the ear, nose, and eye, epidermis, and derivatives of the epidermis (hair, gonads, nails)
beginning of fourth week of development
neural folds are becoming neuropores, somites beginning to form, neural tube forming
neuropores
last areas of neural tube to close; major malformations if not closed
paraxial mesoderm
on either side of neural tube; gives rise to somites
intermediate mesoderm
next to paraxial
intermediate mesoderm derivatives
kidneys, most elements of urinary tract, gonads
somites give rise to _
sclerotome and dermatome
sclerotome
from ventral and medial walls; form vertebral column around neural tube
myotome
dorsolateral and ventrolateral cells; form muscle precursor cells
dermatome
cells between sclerotome and myotome; form dermis
somite derivatives
muscle of the body and limbs, vertebral column and associated musculature, and hypodermis/dermis of skin
lateral plate mesoderm
forms parietal and visceral layers
parietal layer
forms abdominal wall and peritoneal lining
visceral layer
form organs in abdominal cavity
mesoderm gives rise to ALL _
blood vessels
vitelline duct
remains in contact with yolk sac to nourish midgut
endoderm derivatives
epithelium lining of all organs, hepatocytes of liver, enzymes in pancreas
key features of fourth week
pharyngeal arches and somites, neuropores closed, bulge where heart and liver are forming
key features of fifth week
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
key features of sixth week
face taking shape, external ear developing, finger rays forming, heart and liver still bulge
key features of seventh week
more defined face, eyelids forming, lens of eye formed, external ear developed, fingers and toes separating
key features of eighth week
rudiments of all organs have formed, fingers and toes separated, muscle activity begins, eyelids fused, phallus formed
