Notochord develops into?
**Core Concept**
The notochord is a precursor to the vertebral column and plays a crucial role in the development of the axial skeleton. It is a flexible rod-like structure that extends along the length of the embryo, providing a template for the formation of the vertebral bodies and intervertebral discs.
**Why the Correct Answer is Right**
During embryonic development, the notochord induces the formation of somites, which eventually differentiate into sclerotomes. The sclerotomes then migrate and fuse to form the vertebral bodies and intervertebral discs, while the notochord itself degenerates and is replaced by the nucleus pulposus of the intervertebral discs. This process is mediated by the expression of specific genes and signaling pathways, including the Wnt and BMP signaling pathways.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the notochord does not give rise to the limbs or the appendicular skeleton.
**Option B:** This option is incorrect because the notochord does not develop into the central nervous system or the brain.
**Option C:** This option is incorrect because the notochord does not form the cartilage or bone of the joints.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the notochord is a transient structure that eventually degenerates, but it plays a critical role in the development of the vertebral column and the formation of the intervertebral discs.
**Correct Answer: D. Spinal column.