Final answer:
The seminal vesicles, prostate gland, and bulbourethral glands are the three things that add fluids to the ejaculate to form semen. These fluids provide sperm with energy, neutralize vaginal acidity, and help with the motility and survival of sperm.
Step-by-step explanation:
The three things that add fluid to the ejaculate to make semen are the seminal vesicles, the prostate gland, and the bulbourethral glands. These critical accessory glands of the male reproductive system each contribute unique components to the semen. The seminal vesicles secrete a viscous fluid rich in fructose, which provides energy to the sperm cells. The fluid is also alkaline, helping to neutralize the acidity of the vaginal tract, which enhances sperm survival and motility.
The prostate gland contributes a milky fluid that contains enzymes, citric acid, and acid phosphatase. This fluid helps to further nourish the sperm and contains substances that promote the fluidity of the ejaculate, allowing sperm to move more freely.
Finally, the bulbourethral glands, also known as Cowper's glands, produce a clear, mucus-like fluid that lubricates the urethra and neutralizes any traces of acidic urine prior to ejaculation. This pre-ejaculate also plays a role in lubricating the vagina.