Reproduction (Functioning of male reproductive system)

All living organism maintain their populations by reproduction. Most
simple organisms such as bacteria reproduce asexually by cell division
resulting in offspring’s that are genetically identical.

In human beings, reproduction is sexual, involving the fusion of two
reproductive cells, namely a sperm (male gamete) and an egg (female gamete).
If a sperm succeeds in fertilizing an egg, DNA (genetic material) from
each parent combines to create a unique individual. Sexual reproduction results
in an infinite variety of offsprings.

Functioning of male reproductive system

The central role of the male reproductive system is carried out by the
testes, which produce sex cells called spermatozoa or sperms containing
genetic material. The testes produce sperms continuously from puberty onward.

Men remain fertile for a much longer period than women. In addition, the testes
manufactures male sex hormones or androgens which influence sperm
production, fertility and sex drive. Male sex hormones also promote the
secondary sexual characters.

Gametogenic function of testes (male reproductive system)

Factors controlling spermatogenesis: FSH of pituitary gland
stimulates and controls spermatogenesis. It acts on sertoli cells to facilitate
last stages of maturation of spermatids. It further stimulates the production of
androgens such as testosterone.

The LH of the pituitary acts on the Leydig’s cells of the testes that
releases testosterone. The temperature of testes should be maintained at
32oC for an effective production of spermatozoa.

Spermatozoa (male reproductive system)

Each mature spermatozoan is a motile cell . It has an oval flat head
having an acrosome and a large nucleus containing chromosomal material. The
head is followed by a short neck, a body (middle piece) and a long tail.

The middle piece contains spiral mitochondrial sheaths which are the site of energy production. The tail has a main piece and an end piece. The energy for movement is provided by ATP molecule.

Puberty (male reproductive system)

Puberty is a process in sexual development. Once puberty is reached
sperms are manufactured continuously in the two testes at a rate of about 125
million each day.

Puberty occurs between age 12-15 Hormones secreted by the pituitary cause levels of the male sex hormone testosterone to increase, stimulating changes such as general growth, and the development of secondary sexual characters.

Transport of spermatozoa. For reproduction to take place, the sperm must be
transported to the female reproductive system. The mature spermatozoa that are
formed leave each testis through an epididymis, a long coiled tube that lies above and behind each testis.

The sperms are stored in the epididymis and periodically pushed into the vasdeferens the tube that connects an epididymis to an ejaculatory duct.

During sexual activity each vas deferens, contracts and pushes the sperm toward urethra, the tube that connects the bladder to the outside of the body. The sperms are carried in a fluid consisting of secretions from various glands forming a thick seminal fluid or semen.

Semen is a milky mucoid fluid which contains sperms (50 million in single
ejaculate) plus seminal plasma made up of secretions of the seminal vesicles,
prostate, Cowper’s gland and bulbo – urethral glands. Semen provides nutrient
that help to keep the sperm healthy and also serves as a medium for the
spermatozoa to swim.

During arousal, the penis gets enlarged and becomes firm. Muscular
contraction at the have of the penis then forces the sperm through the male
urethra into the vagina during male orgasm.

Hormonal control (male reproductive system)

Male reproductive function is controlled by several hormones.

1. The hypothalamus of the brain controls the release of FSH and LH through
its releasing factors.

2. FSH and LH stimulate the gonads. Hence the gonads produce sperms
and secrete the hormone, testosterone.

3. Testosterone controls further male reproductive functions. It also helps to
develop and maintain secondary sexual characters, such as enlargement of
larynx, deepening of voice, growth of hair and other adolescent changes.
Regulation of testicular function

The hypothalamus, anterior pituitary and testes are interrelated in
testicular functions. FSH from the pituitary stimulates spermatogenesis in the
presence of testosterone. High concentration of testosterone is maintained due
to the presence of androgen binding protein which is secreted by the sertoli cells.
These cells also secrete another hormone called inhibitin which inhibits the action
of testosterone.

Testosterone secretion by Leydig cells is stimulated by LH. The
testosterone has its action on different target cells. It diffuses into the seminiferous tubules and stimulates spermatogenesis and suppresses secretion of LH by acting on hypothalamus and anterior pituitary.