Welcome to Zoology World

balindrakumar033@gmail.com   25/11/2017,Saturday

WELCOME TO ZOOLOGY WORLD

The science or study of animal life. Together with botany, the study of plant life, it forms the science of biology. Zoology is such a vast subject that most zoologists specialize or focus on the study of particular organisms or taxonomic groups. tion of animals.

What is semen:

The products of the testes(spermatozoa) and prostate gland,
alongwith fluid from the seminal vesicle,are collectively known as
semen.

The products of the testes(spermatozoa) and prostate gland, alongwith fluid from the seminal vesicle,are collectively known as semen.It is a milky,viscus and alkaline(pH 7.2-7.7)fluid ejaculated by male reproductive system during orgasm.The volume of ejaculate varies from person to person.Abstinence play a role in this.Each ejaculate measures 3.5 ml and contains 50-150million sperm/ml i.e.,250 million- 525million(average-400million).

The life span of human sperm after ejaculation is 24-48 hrs. Crayopreservation enhances the longevity of sperm.The rate of active movement of sperm is 1.5-3.0mm per minute in uterine endometrium.

Semen has chemicals for nourishing the sperm(e.g.,-fructose), neutralizing the acidity of urethra and vagina(e.g.,-bicarbonate), stimulating movements in female tract(e.g.,-prostaglandins). A person with a sperm count 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.

Hormone control of male reproductive system:

The growth,maintenance and functions of secondary sex organs
(epididymis,vasa deferentia,accessory glands and penis) are
under the control of testosterone hormone secreted by Leydig's cells

The growth,maintenance and functions of secondary sex organs (epididymis,vasa deferentia,accessory glands and penis) are under the control of testosterone hormone secreted by Leydig's cells of testis,while those of seminiferous tubules and leydig's cells are controlled by Follicular Stimulating Hormone(FSH) and Interstitial Cells Stimulating Hormone(ICSH) of anterior pituitary lobe respectively.

Onset of puberty in the male:

Puberty is the period when reproductive organs become functional. It is triggered by the secretion of the hormone testosterone in the testes. This hormone brings about growth and maturation of the secondary sex organs and development of accessory sex characters.The latter induce:

  1. Enlargment of the penisand scrotum.
  2. Broadening of the shoulders.
  3. Growth of body and facial hairs.
  4. Deepening of the voice due to enlargement of layrinx and thickening of vocal-cords.
  5. Increased development of musculature and bones.
  6. Increase in height characteristic of male puberty.

Male sex act

The male sex act involves 3 phase:-

1.Erection:-

Erection of the penis is caused by rush of arterial blood into the empty sinuses of its spongy tissue on sexual excitement.As the spongy tissue distends,it compress the veins,inhibiting the flow of blood out of the tissue.Filling of tissue with blood is called vasocongestion.

2.Copulation:-

Mucus from the urethral glands,Cowper's glands and vaginal glands provides lubrication for copulation.Friction due to rhythmic movements of sexual intercourse stimulate the sensory cells of the glans penis.This stimulation releases semen into the proximal part of urethra by contraction of reproductive glands and ducts.This process is called emission.Then the rhythmic ,wavelike contractions of the muscles at the base of the penis cause forceful discharge,called ejaculation, of semen into the vagina.One ejaculate(about 3ml.) contains 200 to 400 million spermatozoa.Ejaculation marks the climax of copulation.

Orgasm:

At the peak of sexual stimulation,pleasurable sensation,called orgasm. It usually last only a few seconds.

3.Subsidence of erection:

After ejaculation,the arterioles to the penis contract,reducing the blood flow to the penis,and erection subsides.This often takes a few minutes.

Disorders of male reproductive system:-

Only a few are mentioned.

1.Prostatomegaly(Prostatic hypertrophy):

This is enlargement of prostate gland.If often occurs in old age.The enlarged gland may block the urethra,causing frequent night urination (nocturia) or difficult or painful micturition.Prostate cancer is very common in men.It is treated surgically or with drugs.

2.Impotence:-

This is inability of the male to achieve and or maintain erection of the penis long enough to engage in or complete copulation.

3.Sterility:-

In ability of the male's sperm to fertilize to ovum,it may or may not be associated with impotence.Sterility also results from immobility and morphological abnormality of the sperms,and from low sperm count in the semen.

Female reproductive system: