Sunday, July 26, 2020

Human Reproduction - Notes | Class 12 | Part 1: Male Reproductive System

3. HUMAN REPRODUCTION

Reproduction is the production of young ones by an organism. Humans are sexually reproducing and viviparous.

HUMAN REPRODUCTIVE SYSTEM


1. Male Reproductive System


-   It consists of paired testes, Accessory ducts, Accessory glands & external genitalia (penis).



a. Paired testes


-    Primary sex organs that produce sperms & testosterone.

-    Testes are formed within the abdomen. Soon after the birth or at the 8th month of pregnancy they descent into the scrotal sac (scrotum) through inguinal canal.

-    The low temperature (2-2.50 C less than the body temperature) of scrotum helps for proper functioning of testes and for spermatogenesis.

-    Each testis is oval shaped. Length 4-5 cm, width: 2-3 cm.

-    Each testis has about 250 testicular lobules.

-    Each lobule contains 1-3 coiled seminiferous tubules.

-    Seminiferous tubule is lined internally with

·     Male germ cells (spermatogonia): They become sperms.

·    Sertoli cells: They give nutrition to the germs cells.

- The regions outside the seminiferous tubules (interstitial spaces) contain small blood vessels, interstitial cells (Leydig cells) and immunologically competent cells.

-    Leydig cells secrete testicular hormones (androgens).


b. Accessory ducts (Duct system)


-    Include rete testis, vasa efferentia, epididymis & vas deferens. They conduct sperms from testis as follows:

-  Seminiferous tubules → rete testis (irregular cavities) vasa efferentia (series of fine tubules) → epididymis (stores sperms temporarily) vas deferens → join with duct of seminal vesicle to form ejaculatory ducturethra urethral meatus.

-    Urethra receives ducts of prostate and Cowper’s glands.

c. Accessory glands


-    Include a prostate gland, a pair of seminal vesicles and a pair of Cowper’s glands (bulbo-urethral glands).

-    Their collective secretion (seminal plasma) is rich in fructose, Ca and enzymes.

-    Seminal plasma + sperms → semen.

-    Functions of seminal plasma:

·   Helps for transporting sperms.

·   Supplies nutrients to sperms.

·   Provides alkalinity to counteract the acidity of uterus.

·   Secretions of Cowper’s glands lubricate the penis.

-    Secretions of epididymis, vas deferens, seminal vesicle & prostate help for maturation and motility of sperms.


d. Penis (external genitalia)


-    It is a copulatory organ made of erectile spongy tissue.

-    When spongy tissue is filled with blood, the penis erects. It facilitates insemination.

-    The cone-shaped tip of the penis is called glans penis. It is covered by prepuce (foreskin).

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