Write a note on male accessory glands.

(A) The male accessory glands include paired seminal vesicles,a prostate gland,and paired bulbourethral glands. These glands secrete fluids that constitute the seminal plasma.
$1$. Seminal vesicles: These are paired glands located behind the urinary bladder. They produce about $60-70 \%$ of the volume of semen. Their yellowish,viscous secretion is rich in fructose,vitamin $C$,and other substances that provide nourishment to sperm cells. The duct of each seminal vesicle joins the vas deferens to form the ejaculatory duct.
$2$. Prostate gland: This is a single gland located surrounding the urethra at the base of the urinary bladder. Its secretion is milky and slightly acidic/neutral,which helps in activating sperms and enhancing their motility. It enters the urethra through several small ducts.
$3$. Bulbourethral glands (Cowper's glands): These are paired glands located beneath the prostate gland on either side of the urethra. They secrete an alkaline fluid that neutralizes the acidity of the urethra and acts as a lubricant during copulation.
Constitution of semen: Semen is a milky,sticky mixture of sperms and the secretions of these accessory glands. The alkaline nature of semen (pH $7.2$ to $7.6$) helps neutralize the acidic environment of the female reproductive tract. It protects fragile sperms and facilitates their movement. $A$ typical ejaculation contains $2$ to $5 \text{ ml}$ of semen.