Why Sexual Reproduction?

�continuity of the species

�genetic variation

�Gametes (egg or sperm) are produced in the primary sex organs or gonads (ovaries or testes)

�Male and female parts originate from same tissues and same area of the abdomen

The Male Reproductive System

Male Reproductive System�scrotum = sac that testes are suspended in

The Path of Sperm:

1.testes= male gonads

� containing (~250 m) tightly coiled seminiferoustubules

The Path of Sperm:

1.testes= male gonads

� containing (~250 m) tightly coiled seminiferous

tubules

� Tubules produce mature sperm cells by meiosis - called

spermatogenesis

� has interstitial cells that produce testosterone

� before puberty, the tubules are solid cords →become

hollow and start to function with puberty

2. epididymis – place of sperm maturation (including gaining motility) & storage of sperm

� tightly coiled tubules (~5-6m long) just

outside the testes

3. vas deferens = tube takes sperm from epididymis to urethra (through penis)

� First part stores sperm

Path (cont’d)

4. Urethra – carries both urine and semen

� During ejaculation, the bladder is closed off so no urine comes out

Contributory Glands� secrete products that contribute to semen

production

Semen = seminal fluid + sperm

A.Seminal vesicles = between bladder & rectum &

joins vas deferens

� Releases fluid containing

1. Nutrients for sperm (fructose)

2. Prostaglandins – triggers uterus contractions &

aid in sperm movement

Glands (cont’d)B. prostate gland – just below bladder

� Adds an alkaline (base @ pH 7.5) buffer to

protect sperm against acidity of vagina

C. Cowper’s or Bulbourethral gland – just below

prostate

� Adds lubrication for sperm → better

movement

Note: End of glands

�Penis - made up of erectile tissue which fills with blood when excited (an erection)

= transfers sperm to female

�The main difference between male and female systems:

�Males release gametes during sexual activity while females release only during a monthly cycle

Penis Anatomy

Sperm� Acrosome - contains

enzymes to help penetrate

the egg

� Nucleus – transmit genetic

information (23 chromosomes)

� Mitochondria (spiral) to

provide energy for tail

movement

� Tail – swim

Testosterone

�hormone produced mainly by interstitial

cells of the testes

� responsible for primary and secondary sex

characteristics

PRIMARY SECONDARY

Development of vas

deferens and other ducts

Deepening of voice

Maturation of external

genitalia

Distribution of hair

Sperm production Muscle growth

Control of Testosterone

� GnRH (fr. Hypothalamus)= (gonadotropic

releasing hormone) causes anterior pituitary to

release LH and FSH

� LH (luteinizing hormone) - stimulates interstitial cells

(testes) to produce testosterone

� FSH (follicle stimulating hormone) – targets

seminiferous tubules – stimulates sperm production

� All are regulated by negative feedback

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