Question

Name the male reproductive glands, and state how each contributes to the formation of semen. (p. 455)

Short answer

Answer: The male reproductive glands include the testes, epididymis, prostate gland, seminal vesicles, and bulbourethral (Cowper's) glands. The testes produce sperm cells and testosterone; the epididymis nurtures and transports mature sperm cells; the prostate gland provides fluid containing enzymes, proteins, and other substances to protect sperm cells and facilitate their movement; the seminal vesicles secrete fluid containing fructose and other substances to maintain proper chemical environment and support sperm motility; the bulbourethral glands produce a clear, slippery fluid to neutralize any residual acidic urine in the urethra, lubricate the urethra, and ease the passage of sperm cells during ejaculation.

Step-by-step solution

Identify the male reproductive glands

The male reproductive glands include: 1. Testes 2. Epididymis 3. Prostate gland 4. Seminal vesicles 5. Bulbourethral (Cowper's) glands

Describe the role of the testes in the formation of semen

The testes are the primary male reproductive organs. They produce sperm cells and testosterone, a hormone responsible for the development of male sex characteristics and the regulation of sperm production. The testes contribute to the formation of semen by providing sperm cells, which are the essential component for reproduction.

Describe the role of the epididymis in the formation of semen

The epididymis is a tightly-coiled tube located on the back of each testis. After sperm cells are produced in the testes, they are stored in the epididymis, where they mature and develop the ability to swim. Consequently, the epididymis contributes to the formation of semen by nurturing and transporting mature sperm cells, ready for ejaculation.

Describe the role of the prostate gland in the formation of semen

The prostate gland is a walnut-sized gland located below the urinary bladder and in front of the rectum. It produces a thin, milky fluid that makes up around 30% of semen volume. This fluid contains enzymes, proteins, and other substances that help nourish and protect sperm cells and facilitate their movement. Therefore, the prostate gland contributes to the formation of semen by providing essential elements for sperm cell function and survival.

Describe the role of the seminal vesicles in the formation of semen

The seminal vesicles are two small glands located behind the bladder and above the prostate gland. They secrete a thick, yellowish fluid that makes up around 60% of semen volume. This fluid contains fructose, which provides energy for sperm cells, and other substances that help maintain the proper chemical environment and promote sperm motility. Thus, the seminal vesicles contribute to the formation of semen by providing nourishment and support for sperm cells.

Describe the role of the bulbourethral (Cowper's) glands in the formation of semen

The bulbourethral (Cowper's) glands are two pea-sized glands located under the prostate gland, near the urethra's base. They produce a clear, slippery fluid (known as pre-ejaculate) released before ejaculation. This fluid helps neutralize any residual acidic urine in the urethra, lubricates the urethra, and eases the passage of sperm cells during ejaculation. The bulbourethral glands contribute to the formation of semen by preparing the environment for sperm transport.

Key concepts

Formation of Semen

The formation of semen is a finely tuned physiological process that involves the coordinated efforts of various male reproductive glands. Semen is the fluid that carries sperm from the male reproductive system to the female reproductive tract and is composed mainly of sperm cells and seminal plasma.

The seminal plasma, in particular, plays a crucial role in the viability and function of sperm cells upon ejaculation. It is a combination of secretions from the seminal vesicles, prostate gland, and bulbourethral glands, which all contribute to the final composition of semen. This composite fluid is essential for protecting sperm, providing energy, and ensuring the proper environment for sperm mobility and fertilization capability.

Sperm Production

Sperm production, or spermatogenesis, occurs in the testes, which are the primary male reproductive organs. Within the testes are fine coiled tubes called seminiferous tubules, where immature sperm cells go through several stages of development. Once sperm development is complete, they are sent to the epididymis, where they achieve full maturation and motility.

The process of sperm production is highly dependent on testosterone, a critical hormone also produced in the testes. This hormone regulates the production of sperm and is vital for maintaining male fertility. The mature sperm are then stored in the epididymis until ejaculation, at which point they combine with the seminal plasma to form semen.

Prostate Gland Function

The prostate gland serves a critical function in the male reproductive system. It secretes a milky fluid that, upon mixing with the sperm and the fluid from the seminal vesicles, becomes part of the semen. This prostatic fluid makes up about one-third of the total semen volume and is rich in enzymes, including prostate-specific antigen (PSA), which helps to liquefy the semen after ejaculation.

Prostatic secretions are alkaline, which counteracts the acidic environment of the female reproductive tract, enhancing sperm survival and maximizing the potential for fertilization. The health of the prostate is, therefore, essential for maintaining reproductive capabilities, as it supports the adequate production and function of semen.

Seminal Vesicles Contribution

The seminal vesicles play a substantial role in semen composition by providing the majority of seminal fluid's volume. Their secretion is a viscous, alkaline fluid that contains fructose and other sugars to fuel sperm. It also includes prostaglandins, which are believed to help widen the cervix, making it easier for sperm to enter the uterus.

Furthermore, the fluid from the seminal vesicles contains amino acids, citrate, and flavins, which contribute to the characteristic yellowish color of semen. Collectively, the seminal vesicles' contributions ensure that sperm cells have the necessary energy resources and environmental conditions to remain viable until they reach the egg for potential fertilization.

Bulbourethral Glands Role

Although the bulbourethral glands, also known as Cowper's glands, are small, their role in semen formation is not trivial. They are responsible for producing a clear fluid that is released during sexual arousal prior to ejaculation. This pre-ejaculate fluid serves several purposes: it neutralizes traces of acidic urine in the urethra, acts as a lubricant for spermatozoa during their passage, and reduces friction during sexual intercourse.

The activity of the bulbourethral glands is particularly important in optimizing the conditions for sperm transport by preparing a safer and more accommodating pathway for the sperm to travel through the urethra during ejaculation.