**Question:** Posterior cord supplies

**Core Concept:** The posterior cord is a segment of the spinal cord that plays a crucial role in transmitting sensory information from the lower limbs and trunk to the central nervous system. Understanding its supply is essential in assessing spinal cord injuries.

**Why the Correct Answer is Right:** The correct answer is **D:** the posterior spinal artery supplies the posterior cord of the spinal cord.

The posterior spinal artery is a branch of the vertebral artery, which in turn arises from the internal carotid artery. It supplies the posterior aspect of the spinal cord, ensuring adequate oxygen and nutrient delivery to maintain its function.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Anterior spinal artery):** Although the anterior spinal artery also supplies the spinal cord, it supplies the anterior aspect, not the posterior cord.

B. **Option B (Medulla oblongata):** The medulla oblongata is part of the brainstem, not related to spinal cord circulation.

C. **Option C (Sacral nerve roots):** Sacral nerve roots are the efferents of the spinal cord, carrying motor information, not the spinal cord itself.

**Clinical Pearl / High-Yield Fact:**

In clinical scenarios, understanding posterior spinal artery supply aids in assessing spinal cord injuries, specifically when evaluating the extent of damage to the posterior columns. A compromised posterior spinal artery can lead to posterior spinal cord ischemia and subsequent neurological deficits.

**Correct Answer:** The correct answer is D, the posterior spinal artery, as it directly supplies the posterior cord of the spinal cord, ensuring its normal function. The anterior spinal artery, medulla oblongata, and sacral nerve roots are incorrect because they are unrelated to spinal cord circulation and the posterior cord specifically. Understanding these arterial supplies aids in assessing spinal cord injuries and analyzing the extent of damage to the posterior columns.