Which gland surrounds the male urethra and secretes a fluid that is part of the ejaculatory fluid?

The prostate gland is the correct answer as it is situated around the male urethra and plays a crucial role in male reproductive health. It secretes a fluid that is a significant component of semen. This prostatic fluid helps to nourish and transport sperm during ejaculation. The prostate gland's secretion contributes to the overall volume of ejaculate and provides a medium for the sperm to swim, enhancing fertility.

In contrast, the bulbourethral gland, also known as Cowper's gland, is located near the base of the penis and produces a pre-ejaculate fluid, but it does not surround the urethra nor does it contribute to the ejaculate in the same way that the prostate does. The seminal vesicles produce a fluid rich in sugars that nourishes sperm and makes up a large part of the semen, but they are not directly surrounding the urethra. The pituitary gland, on the other hand, is an endocrine gland located in the brain and is involved in hormone regulation but does not produce any fluids related to ejaculation.