**Question:** All are derived from neural crest except ?

Core Concept:
Neural crest is a transient embryonic structure that arises from the edge of the neural plate during embryonic development. It plays a crucial role in the formation of various structures, including the peripheral nervous system, craniofacial bones, and connective tissues.

Why the Correct Answer is Right:
The correct answer is "D." Embryonic cells derived from the neural crest are known as neural crest cells or melanoblasts. These cells contribute to various structures, including the peripheral nervous system and craniofacial bones. However, melanoblasts are not involved in the formation of melanocytes, which are responsible for skin pigmentation.

Why Each Wrong Option is Incorrect:
A. Neural crest cells: Neural crest cells are indeed derived from the neural crest, making this option incorrect.
B. Neural tube: The neural tube is an embryonic structure that precedes the neural crest, not derived from it.
C. Somites: Somites are involved in the formation of vertebrae and ribs, not melanocytes.

Clinical Pearl / High-Yield Fact:
Melanin is the pigment produced by melanocytes, giving color to the skin, hair, and eyes. Understanding the embryonic origins of melanocytes is crucial for understanding skin pigmentation disorders like vitiligo and certain congenital anomalies.

Correct Answer:
**D.** Melanocytes.

Explanation: Melanocytes are derived from the neural crest and are responsible for producing melanin, the pigment that gives color to the skin, hair, and eyes. They are not formed from the neural crest, which is why melanocytes are an exception to the statement that all structures derived from the neural crest are involved.