The Basics of the Origin of Life – Male

The testicles lie outside of the abdomen, suspended in a fleshy sack called the scrotum. Testes are made from the same embryonic material that becomes the ovaries in the female. The testes develop within the abdomen, but about two months before birth they descend through the abdominal wall into the scrotum. The testes are connected to the body through scrotal tissue and two spermatic cords that are composed of nerves, blood vessels and the vas deferens, or sperm ducts.

The functions of the testes are to produce sperm and the male sex hormone testosterone. In order to produce and nurture sperm, the temperature within the testes must remain approximately 1-2�C cooler than normal body temperature. Part of the function of the scrotum is to maintain this optimal temperature by holding the testes further from the body during warm weather or contracting and bringing them closer to the body during cold weather.

The seminal vesicles are two pouches located in the pelvic region behind the urinary bladder. Their primary purpose is to supply a viscous, alkaline secretion that forms a part of the seminal fluid. Seminal fluid is often referred to as semen and includes secretions from the seminal vesicles, prostate and bulbourethral glands, as well as sperm cells. The seminal vesicles supply about 30% of the seminal fluid volume. The fluid from the seminal vesicles is rich in nutrients, including citric and amino acids and fructose to provide an energy source for sperm metabolism and to enhance sperm motility.

The prostate gland, the largest of all the male reproductive glands, is chestnut-sized and located just below the bladder, near the exit of the urethra. The prostate contributes about 60% of the seminal fluid, secreting a thin, milky-white alkaline fluid similar to that of the seminal vesicles. The fluid is discharged into the urethra during ejaculation to help neutralise the acidic fluids in the male urethra and the female vagina. This function is important because acids can have an adverse effect on sperm and, at higher concentrations, can kill them.

The ejaculatory ducts are two short tubes that descend through the prostate gland and into the urethra. They are formed by the union of the vas deferens and the ducts of the seminal vesicles. The following figure shows the formation of the ejaculatory ducts.

The urethra is a tube running from the bladder through the prostate gland to the end of the penis, forming the final section of the seminal fluid passageway. The urethra functions as the exit point for both semen and urine. The closing of muscular sphincters automatically blocks the flow of one process when the other is occurring.

The bulbourethral glands (sometimes called Cowper’s glands) are two pea-sized glands located just below the prostate. They also secrete an alkaline fluid, although it amounts to less than 5% of the seminal fluid volume.

The penis is the male organ through which both sperm and urine pass from the body. It is covered by a loose layer of skin and is composed of sponge-like erectile tissue containing large sinuses interspersed with veins and arteries. During sexual stimulation, the arteries dilate and the penis becomes erect as the spongy tissues fill with blood. The tissue at the end of the penis forms the glans penis. In an uncircumcised male, a fold of loose skin called the foreskin covers the glans penis. In the process of ejaculation, the penis delivers sperm contained in seminal fluid into the female’s body for fertilization of the ovum.