Human
Reproduction
,Human Reproduction
Sexual reproduction involves production of male & female sex cells, gametes.
In humans, separate sexes, each with special organs to develop gametes for
fertilisation. Male gamete: sperm. Female gamete: ovum (plural: ova).
Male reproductive system
Human reproductive system is typical of mammalian reproductive system.
Development of external reproductive organ, penis, evolved to ensure transfer of male
gametes (sperm) into female reproductive tract, internal fertilisation takes place.
Sperm combines with egg, contributes half genetic material offspring & determines sex
Roles of male reproductive system:
• produce sperm in male gonads, testes
• produce male sex hormone, testosterone
• deliver sperm (in liquid medium semen) during copulation.
Consists of:
Pair of testes, in scrotum
Epididymis, vas deferens, ejaculatory duct & urethra
Seminal vesicles, prostate gland, Cowper's glands, penis.
The Testes
Singular, testis. Occur in bag-like scrotum, lies outside abdominal cavity.
Scrotum protects testes, regulates temp 2-3 ° below body temp (37°)
Optimal sperm production, ≈34°
Within each testis are seminiferous tubules, lined by germinal epithelium cells, produce
spermatozoa (sperm cells) by spermatogenesis (meiosis).
Inside seminiferous tubules, specialised cells called Sertoli cells, rich in glycogen.
Believed glycogen serves as nutrient for spermatids as develop to sperm cells/spermatozoa.
Between seminiferous tubules are interstitial cells, cells of Leydig, secrete male sex hormone,
testosterone (important in male secondary sexual characteristics).
, When sexual maturity/puberty occurs (11-15 years), testosterone develops male
characteristics: growth hair on face, armpits, pubic areas, lowering voice & development
of muscles gives characteristic shape.
Before puberty, GH or STH, responsible for growth of body.
After puberty, testosterone plays role in body development.
Epididymis is coiled tube (5cm long) lying outside each testis, within scrotum.
Leads from seminiferous tubules, stores sperms (till mature) & passes into vas deferens.
Vas deferens/sperm duct carries spermatozoa from epididymis to ejaculatory duct.
Spermatic Cord
Vas deferens, blood vessels & nerves of testis wrapped in covering muscle
Vas deferens enters urethra (leads from bladder) after urethra left bladder
Accessory glands
Semen = sperm cells + seminal fluid secreted by seminal vesicle, prostate gland & Cowper’s gland
Seminal Vesicles
Before each sperm duct joins urethra, receives secretion from glandular vesicle.
Function: secretes fluid, contains glucose & amino acids (nutrients/energy), helps Seminal
Vesicles
movement of spermatozoid.
Prostate Gland
Situated at exit (neck) of bladder.
Function: secretes milky alkaline fluid, neutralise acid in urethra (in urine) & in female's body
Cowper's Gland
Two small Cowper's glands on either side of urethra, just below prostate gland.
Function: secrete protective mucous substance into urethra, lubricates head of the sperm.
Penis
Organ responsible for transfer of sperm, consists of connective tissue containing
blood spaces (called sinuses), tissue of penis is described as spongy tissue.
Erection essential for effective transfer of sperm cells/semen.
