The Male Reproductive System - Accessory Glands

Accessory Glands:

• The accessory glands of the male reproductive system include the paired seminal vesicles and bulbourethral glands also called Cowper’s gland and a single prostate gland. 

1) Seminal vesicles:

• Seminal vesicles are muscular pouches that release spermatozoa activating chemicals such as fructose, citrate, inositol, prostaglandins, and numerous proteins.
• Sperms utilise fructose as a respiratory substrate.
• Sperm viability and motility are maintained by seminal fluid.
• The seminal vesicle secretes an alkaline, nourishing fluid that makes up the majority of the semen (60%). It is also known as uterus-masculinus. It develops from the embryo's mullerian duct. These ducts combine to create oviducts in females.
• The seminal vesicle does not contain sperm.
• Seminal vesicles are situated between the rectum and the urine bladder.
• Test for rape: Fructose, which is found in seminal fluid but not produced elsewhere in the body, can be used as a forensic test for rape. Its presence in the female vaginal canal indicates sexual activity.

2) Prostate Gland:

• The prostate gland is located around the first section of the urethra. This gland secretes a mildly acidic fluid (pH around 6.5) that accounts for 25% of the semen.
• The secretion nourishes and stimulates the spermatozoa, allowing them to swim.
• It is required for sperm motility (removal causes sterility).
• Fibrinogen and Fibrinolysin are present in the secretion of the prostate–gland citric acid, calcium, and phosphate.
• The prostate gland secretion interacts with the seminal vesicle secretion, causing the semen to coagulate.
• Sperm motility is limited in coagulated semen, resulting in energy conservation.
• After a while, fibrinolysin causes the semen to liquefy anew, allowing the sperms to migrate. 

3) Cowper's glands:

• Cowper's glands are also termed Bulbourethral glands.
• The first pair of Cowper's glands are attached to urethra.
• They secrete alkaline mucus which is discharged into the spongy part of urethra.
• The mucus lubricates the reproductive tract. This serves to neutralize any acid of urine remaining in the urethra.
• Secretion of Cowper's glands is produced before the ejaculation of semen.
• Secretion of Cowper's glands carries some spermatozoa released before ejaculation. This is one of the reasons for the high failure rate of the withdrawal method of birth control. 

4) Perineal or Rectal glands:

• These are found both in males and females during the breeding season, these glands secrete an odoriferous liquid that has pheromones or Ectohormones in it.
• Its smell attracts animals of the opposite sex, found in herbivorous and carnivorous mammals.
• In man, Perineal or Rectal glands are absent. 

5) Other glands:

• Prepuce contains preputial glands which produce a sebaceous substance that together with desquamated epidermal cells forms a whitish, pasty, foul-smelling accumulation, called smegma, about the base of the glans penis beneath the prepuce. 

Semen:  

• Semen or seminal fluid is a milky white fluid which contains sperms and the seminal plasma (secreted from the seminal vesicles, prostate gland, and bulbourethal glands).
• The seminal fluid acts as a transport medium provides nutrients, contains chemicals that protect and activate the sperms, and also facilitates their movement.
• It is a milky, viscus, and alkaline (pH7.7) fluid ejaculated by the male reproductive system during orgasm.
• The volume of ejaculate varies from person to person.
• Abstinence plays a role in this. Each ejaculate measures 1.5-3.5 ml and contains 50-150 million sperm/ml i.e., 250 million-525 million (average 400 million).
• The life span of human sperm after ejaculation is 24-48 hrs.
• Cryopreservation enhances the longevity of sperm.
• The rate of the active moment of sperm is 1.53 mm per minute in uterine endometrium.
• Semen has chemicals for nourishing the sperms (e.g., - fructose), neutralizing the acidity of the urethra and vagina (e.g., bicarbonate), and stimulating movements in the female tract (e.g., - prostaglandins).
• The pH of semen is 7.7.
• A person with sperm counts below 20 million will be physiologically sterile.
• Fusion of defective sperm (e.g., 22+xy with ovum causes many birth defects e.g., klinefelter's syndrome). They are created by the cellular division process known as meiosis, which creates 4 sperm from a single germ cell. They’re also very small, only about 50μm long.