## Notochord and Its Derivatives The **notochord** is a mesodermal structure that appears during the third week of development and plays a crucial role in induction and patterning of the embryo. ### Key Derivatives of the Notochord: - **Nucleus pulposus** of intervertebral discs (primary derivative) - Contributes to the formation of the body of the vertebrae (minor contribution) - Degenerates in most other regions ### Clinical Pearl: The nucleus pulposus retains notochordal remnants throughout life. Notochordal remnants can persist and give rise to **chordomas** — rare malignant tumors found along the midline, particularly in the sacrococcygeal region and skull base. ### High-Yield Fact: While the notochord induces formation of the vertebral column and spinal cord, it does **not** directly form the vertebral bodies (which arise from sclerotomes of somites) or the spinal nerves (which arise from neural crest). The notochord's primary lasting contribution is the nucleus pulposus. **Citation:** Langman's Embryology 14e, Chapter 8 (Skeletal System)
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