###Rationale: - Neural crest cells themselves are coming from epiblasts which contribute to numerous structures in body like peripheral nervous system etc. Derivatives of Neural Crest Cells: - Sensory neurons of cranial ganglia - V, VII, VIII, IX, X - Sensory neurons of spinal dorsal root ganglia & their peripheral sensory receptors - Satellite cells in all sensory ganglia - Sympathetic ganglia & plexuses - Neurons & satellite cells - Parasympathetic ganglia & plexuses - Neurons & satellite cells - Enteric plexuses - Neurons & glial cells - Schwann cells of all peripheral nerves - Medulla of suprarenal gland, chromaffin cells - Carotid body type I cells (and type II, satellite type cells) - Calcitonin-producing cells ( c-cells) - Melanocytes - Mesenchymal derivatives in the head - Frontal, parietal, squamous temporal, nasal, vomer, palatine bones, maxillae & mandible - meninges - Choroid, sclera, iris & ciliary body (controversial) (Iris muscles- Sphinctor & dilator pupillae - from neural plate ectoderm) - Connective tissue of lacrimal, nasal, labial, palatine, oral & salivary glands. - Dentine of teeth (odontoblasts - Connective tissues of head, including cailage, ligaments & tendons - Connective tissues of thyroid gland & of pharyngeal pouches i.e, parathyroid glands & thymus - Tunica media of outflow tract of hea & the great vessels.

###Answer: OPTION C IS CORRECT.
###Question: All are Neural crest derivatives EXCEPT
###Options:
A. Odontoblasts
B. Sympathetic ganglia
C. Iris muscles
D. C cells of thyroid gland
