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 duct → urethra → 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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