**Question:** Trapezius is supplied by

A. Cervical region of the spinal cord
B. Thoracic outlet
C. Shoulder girdle
D. Intercostal nerves

**Correct Answer:** D. Intercostal nerves

**Core Concept:**
The trapezius muscle is a large, flat, triangular muscle located on the posterior aspect of the neck and upper back, responsible for extending and rotating the head, and depressing and retracting the scapula. It is composed of three parts: superior, middle, and inferior trapezius.

**Why the Correct Answer is Right:**
The trapezius muscle is supplied by the intercostal nerves. In the thoracic outlet, the intercostal nerves (T1-T12) arise from the spinal cord's anterior rami, passing through the subclavian artery, pectoralis minor muscle, and the first rib to reach the trapezius muscle.

**Why Each Wrong Option is Incorrect:**
A. Cervical region of the spinal cord: The trapezius muscle is part of the somatic nervous system and does not directly receive its supply from the spinal cord.

B. Thoracic outlet: Although the intercostal nerves pass through the thoracic outlet, they do not directly supply the trapezius muscle. Instead, they pass through this region to supply the upper limb muscles.

C. Shoulder girdle: The trapezius muscle is part of the shoulder girdle, but it is supplied by the intercostal nerves, not the nerves of the shoulder girdle.

**Clinical Pearl:**
Understanding the anatomy of the intercostal nerves and their role in supplying the trapezius muscle is crucial for recognizing and treating thoracic outlet syndrome, which is characterized by pain, paresthesia, and/or numbness in the upper extremity due to compression of the intercostal nerves in the thoracic outlet. Thoracic outlet syndrome should be considered in patients presenting with these symptoms in the upper limb, especially when they occur during arm abduction or elevation.