Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

What is the relation between dermatome T4 and the body?

1. Covers the thumb

2. Covers the middle finger

3. Covers the nipple

4. Covers the xyphoid process

The correct answer is: Covers the nipple

The correct answer relates to the sensory distribution of dermatomes, which are specific areas of the skin innervated by sensory fibers of a single spinal nerve root. The T4 dermatome is particularly known for its correspondence with the level of the nipple on the human torso. This means that if one experiences sensory changes or issues in the T4 dermatome, it might coincide with sensations felt at the nipple area. Understanding the intimacy of dermatomes and the areas they affect is crucial in clinical practice, especially in diagnosing conditions related to nerve injury or diseases that may have cutaneous manifestations. Recognizing that the T4 level corresponds with the nipple helps clinicians localize issues effectively in both neurological and surgical contexts. In contrast, the other options relate to different dermatomes: the thumb is typically associated with the C6 dermatome, the middle finger aligns with C7, and the xyphoid process is innervated by T7. This illustrates how specific regions of the body are mapped to distinct spinal nerve roots, emphasizing the importance of understanding these mappings in clinical assessments.