Ectoderm Derivatives

Ectoderm

Epidermis:

• The skin, specifically the surface layer (meaning NOT the dermis, the underlying layer)
• The skin appendages (eg, the hair, nails, and other appendages).

The neural crest cell derivatives:

• Select cranial nerves the pharyngeal arch derivatives (which are cranial nerves 5, 7, 9, and 10).
• The dorsal root ganglia, which are the pseudounipolar sensory neurons.
• The sympathetic chain ganglia, which supply the sympathetic portion of the autonomic nervous systems, responsible for "Fight or Flight".
• The adrenal medullary cells, which are activated along with the sympathetic nervous system during stress.
• The enteric nervous system, which is the intrinsic nervous system activator of the gut.
• Additional nerve and cartilaginous derivatives.

Neural tube derivatives and the placodes (which are ectodermal thickenings):

From cranial to caudal, they are the:

• Telencephalon
• Diencephalon
• Mesencephalon
• Metencephalon
• Myelencephalon
• The caudal neural tube

* The Telencephalon and Diencephalon derive from the prosencephalon.

* The metencephalon and myelencephalon derive from the rhombencephalon.

• Key placodes (which are areas of thickened surface ectoderm), which form CNs 1, 2, and 8 (the solely sensory set of CNs), from cranial to caudal
  • At the nasal prominences lies the olfactory placode, which derives the olfactory epithelium and olfactory nerve (CN 1).
  • The optic placode forms the optic nerve (CN 2); it originates from the diencephalon.
  • The otic placode forms the vestibulocochlear nerve (CN 8); it originates from the hindbrain.