Which of the following germ layers gives rise to the nervous system, epidermis, and tooth enamel?

Explanation

## Germ Layer Derivatives The **ectoderm** is the outermost of the three primary germ layers formed during gastrulation (week 2–3). It gives rise to multiple important structures: ### Ectodermal Derivatives: - **Nervous system**: Brain, spinal cord, and peripheral nerves (via neural tube) - **Epidermis**: Outermost layer of skin - **Tooth enamel**: Ameloblasts derived from oral ectoderm - Hair, nails, sebaceous glands - Sensory organs (eye, ear, nose) - Cranial and spinal nerves ### Why This Matters: The ectoderm is the source of the entire nervous system and integumentary system. Defects in ectodermal induction (e.g., neural tube defects) result in anencephaly or spina bifida. **Key Point:** Remember the mnemonic **"Ectoderm = Outer layer"** — it forms all structures that interface with the external environment.