Okay, let's tackle this question. The user is asking about the prostatic urethra and which statement is not true. First, I need to recall the anatomy of the male urethra. The male urethra is divided into three parts: the prostatic, membranous, and spongy (penile) parts. The prostatic urethra is the first part, passing through the prostate gland.

The question is asking for the exception, so I need to figure out which of the options is not a feature of the prostatic urethra. Let me think about the key features of the prostatic urethra. It's the widest and most dilatable part of the urethra. It contains the ejaculatory ducts opening into it, which carry sperm from the seminal vesicles and vas deferens. Also, the verumontanum is a landmark here, where the prostatic utricle is located. The prostatic urethra is surrounded by the prostate gland, so it's not surrounded by smooth muscle. The membranous part is the part that's surrounded by the external urethral sphincter, which is made of skeletal muscle. Wait, the prostatic urethra is surrounded by the prostate, which is glandular tissue, not smooth muscle. So if one of the options says it's surrounded by smooth muscle, that would be incorrect. Also, the prostatic urethra is not the narrowest part; the narrowest is the membranous part. Another point is that the prostatic urethra is lined with transitional epithelium, while the other parts have different linings.

So possible incorrect options could be something like "it is the narrowest part," "it is surrounded by smooth muscle," or "it lacks mucous glands." Let me check each option. Suppose the options are:

A. It is the widest part of the urethra. Correct because it's the most dilatable.

B. It is surrounded by smooth muscle. Incorrect because the prostate is glandular and fibromuscular tissue, but not primarily smooth muscle. The external sphincter is in the membranous part.

C. It contains the verumontanum. Correct.

D. It is lined by transitional epithelium. Correct.

So the incorrect answer would be B. Therefore, the correct answer is B. The explanation would note that the prostatic urethra is surrounded by the prostate gland, which includes fibromuscular tissue, but the main muscle around it isn't smooth muscle. The membranous part has the external urethral sphincter made of skeletal muscle. The clinical pearl would be that the prostatic urethra's width makes it less prone to strictures compared to the membranous or spongy parts. Also, the presence of the ejaculatory ducts and verumontanum is a key feature.

**Core Concept**
The male urethra is anatomically divided into prostatic, membranous, and spongy (penile) segments. The **prostatic urethra** is the widest and most dilatable portion, traversing the prostate gland and containing the ejaculatory ducts and verumontanum. It is lined by transitional epithelium and surrounded by fibromuscular tissue of the prostate, not smooth muscle.

**Why the Correct Answer is Right**
The

✓ Correct Answer: B. Presents a concavity posteriorly