why sexual reproduction? · male reproductive system scrotum = sac that testes are suspended in the...
TRANSCRIPT
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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