Embryologic derivatives

Question 1

Surface ectoderm

Answer 1

Ectoderm

Epidermis

adenohypophysis (from Rathe pouch)

lens of eye

epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium

anal canal *below the
pectinate line

parotid, sweat, mammary glands.

*Craniopharyngioma—benign Rathke pouch tumor with cholesterol crystals, calcifications

Question 2

Neuroectoderm

Answer 2

Ectoderm

Brain (neurohypophysis, CNS neurons, oligodendrocytes,
astrocytes, ependymal cells, pineal gland)

retina and optic nerves

spinal cord

“Neuroectoderm—think CNS”

Question 3

Neural crest

Answer 3

Ectoderm

PNS (dorsal root ganglia, cranial nerves, autonomic ganglia, Schwann cells)

melanocytes - in skin

chromaffin cells of adrenal medulla

parafollicular (C) cells of thyroid

pia and arachnoid matter
bones of the skull

odontoblasts - produces dentin in teeth

aorticopulmonary septum
endocardial cushions

“Neural crest—think PNS and non-neural structures nearby”

Question 4

Mesoderm

Answer 4

Muscle, bone, connective tissue

serous linings of body cavities (eg, peritoneum)

spleen (derived from foregut mesentery)
kidneys
adrenal cortex

cardiovascular structures

lymphatics, blood

wall of gut tube

upper vagina

dermis

testes, ovaries

Mesodermal defects = VACTERL:
Vertebral defects
Anal atresia
Cardiac defects
Tracheo-Esophageal fistula
Renal defects
Limb defects (bone and muscle)

Question 5

Endoderm

Answer 5

Gut tube epithelium (including anal canal
*above the pectinate line)

most of urethra and lower vagina (derived from urogenital sinus)

luminal epithelial derivatives (eg, lungs, liver, gallbladder, pancreas, eustachian tube,
thymus, parathyroid, thyroid follicular cells).