**Core Concept**
The striae of Retzius are a series of longitudinal grooves on the anterior surface of the urinary bladder. They are formed by the contraction and relaxation of the detrusor muscle during the filling and emptying phases of the bladder. The striae of Retzius are an important anatomical landmark in urology and are often used as a key feature in the identification of the bladder.

**Why the Correct Answer is Right**
The striae of Retzius are formed by the contraction and relaxation of the detrusor muscle, which is the smooth muscle layer of the bladder wall. During the filling phase, the detrusor muscle relaxes, allowing the bladder to fill with urine. As the bladder fills, the striae of Retzius become more pronounced. During the emptying phase, the detrusor muscle contracts, causing the bladder to empty and the striae of Retzius to become less pronounced. The striae of Retzius are an important indicator of bladder function and are often used in the diagnosis of various bladder disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** This option may be a distractor that seems plausible but is actually incorrect. However, without the actual text, I'll wait for it before explaining.

**Option B:** This option may be a distractor that is incorrect because it contradicts the established knowledge about the striae of Retzius. However, without the actual text, I'll wait for it before explaining.

**Option C:** This option may be a distractor that is incorrect because it is unrelated to the striae of Retzius. However, without the actual text, I'll wait for it before explaining.

**Option D:** This option may be a distractor that is incorrect because it is contradictory to the established knowledge about the striae of Retzius. However, without the actual text, I'll wait for it before explaining.

**Clinical Pearl / High-Yield Fact**
The striae of Retzius are an important anatomical landmark in urology and are often used as a key feature in the identification of the bladder. They are formed by the contraction and relaxation of the detrusor muscle during the filling and emptying phases of the bladder.

**Correct Answer:**