**Core Concept**
The incremental lines of Retzius are a histopathological feature used to diagnose certain conditions. They are characterized by incremental or step-like lines of calcification seen in the walls of small blood vessels, particularly arterioles and capillaries. This phenomenon is often associated with aging and is observed in various systemic conditions.

**Why the Correct Answer is Right**
The incremental lines of Retzius are formed due to the deposition of calcium salts within the walls of small blood vessels. This process is thought to be related to the aging process and is influenced by factors such as hypertension and atherosclerosis. The incremental lines are visible under light microscopy and are an important diagnostic feature in conditions such as malignant hypertension and diabetic microangiopathy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the incremental lines of Retzius. While calcification can occur in various tissues, the incremental lines of Retzius are a specific feature of small blood vessel walls.
**Option B:** This option is incorrect because the incremental lines of Retzius are not associated with inflammation. While inflammation can cause vascular damage, it is not directly related to the formation of incremental lines.
**Option C:** This option is incorrect because the incremental lines of Retzius are not a feature of normal aging. While aging can contribute to vascular calcification, the incremental lines of Retzius are a specific histopathological feature that is observed in certain systemic conditions.

**Clinical Pearl / High-Yield Fact**
The incremental lines of Retzius are an important diagnostic feature in conditions such as malignant hypertension and diabetic microangiopathy. They can be seen under light microscopy and are often associated with vascular calcification and damage.

**Correct Answer: D.