Final answer:
The accessory glands that add fluid to sperm cells to form seminal fluid are the seminal vesicles, the prostate gland, and the bulbourethral glands. The seminal vesicles secrete 70% of semen, the prostate gland secretes about 30%, and the bulbourethral glands secrete a small amount to help lubricate the urethra.
Step-by-step explanation:
The accessory glands that add a viscous fluid to the sperm cells to form seminal fluid are the seminal vesicles, the prostate gland, and the bulbourethral glands.
The seminal vesicles secrete an alkaline fluid that makes up about 70 percent of semen, providing substances and nutrients that the sperm need for survival and motility.
The prostate gland secretes an alkaline fluid that makes up close to 30 percent of semen, and it contains a high concentration of zinc, which is essential for sperm health and motility.
The bulbourethral glands secrete a small amount of fluid into semen, which helps to lubricate the urethra and neutralize any acidic urine in it.