Final answer:
The seminal vesicles and prostate gland secrete an alkaline fluid that contains fructose, enzymes, and prostaglandins into the ejaculatory ducts. These secretions constitute the majority of semen and are essential for sperm survival and motility within the female reproductive system.
Step-by-step explanation:
Accessory Glands and Semen Composition
The seminal vesicles and prostate gland are responsible for secreting an alkaline fluid into the ejaculatory ducts. This secretion is composed of several substances that are vital for the survival and motility of sperm within the female reproductive tract. The seminal vesicles, located at the posterior border of the urinary bladder, contribute about 60 to 70 percent of the semen's volume. Their secretion is high in fructose, which serves as an energy source for sperm, and prostaglandins, which are thought to influence the female reproductive tract to assist sperm in reaching the ovum.
The prostate gland surrounds the urethra and is located just below the seminal vesicles. It adds approximately 30 percent to the semen volume, producing a slightly alkaline fluid rich in zinc and enzymes like prostate specific antigen (PSA), which plays a role in semen liquefaction post-ejaculation. The prostate's secretions are crucial for maintaining the health and motility of the sperm.
In the process of ejaculation, sperm from the vas deferens mix with the fluids from the seminal vesicles and prostate gland in the ejaculatory ducts, forming semen, which then passes through the urethra during ejaculation. The combined alkaline nature of these fluids is essential, as it neutralizes the acidic environment of the vaginal tract, facilitating effective sperm motility.