An X ray shows that a patient has a region in her upper spine where several vertebrae are fused on one side, causing curvature of the spine.The doctor tells her that the defect occurred during embryogenesis when
A) the notochord failed to form individual blocks of tissue on one side.
B) a portion of several somites on one side fused.
C) neural crest cells migrated along abnormal pathways on one side.
D) the neural tube failed to form the vertebrae properly on one side.
E) cells from the lateral portion of the neural plate failed to fuse with cells on the opposite side in one region of the neural plate.

Question

Quizplus · Accepted Answer

The curvature of the spine due to several vertebrae being fused on one side is most accurately explained by a defect in the somites during embryogenesis. Somites are blocks of mesoderm that segment along the embryo's axis and give rise to the vertebrae, among other structures. If a portion of several somites on one side fused abnormally, it could lead to the described spinal curvature.

An X Ray Shows That a Patient Has a Region