**Question:** External nose is formed from which structures?

**Core Concept:** The external nose is a prominent part of the human face and is composed of several structures during development. In adults, it primarily serves as the entry point for air into the respiratory system.

**Correct Answer: C. Nasal Septum, Mucous Membrane, and Cartilage**

**Why the Correct Answer is Right:** During embryonic development, the external nose originates primarily from two structures: the nasal septum (from the first pharyngeal arch) and the nasal mucous membrane (from the second and third pharyngeal pouches). The cartilage framework of the nose is formed by the nasal process of the maxilla and the nasal process of the frontal process of the lower jaw (zygomatic arch).

**Why Each Wrong Option is Incorrect:**

A. **Nasal Mucosa:** While the mucous membrane does contribute to the external nose, it is not the primary component.
B. **Nasal Cartilage:** While cartilage is important for the structural integrity of the nose, it does not form the entire external nose.
D. **Nasal Septum:** Although the nasal septum is involved in the formation of the external nose, the correct answer includes more structures.

**Clinical Pearl:** The external nose consists of a combination of developmental structures, emphasizing the importance of understanding embryology and the interplay between different structures during development. This knowledge is crucial for understanding various congenital malformations and their implications for clinical practice.

**Example:** Cleft lip and palate are common examples of developmental abnormalities involving the external nose. Knowledge of embryology helps in understanding the underlying cause and management strategies for these conditions.