Download Comparative Vertebrate Physiology

Human Anatomy and
Physiology
Reproduction in males
Reproduction
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Dormant until puberty
Manufacture and delivery of sperm
Hormones : testosterone, gonadotropic
hormones, androgens
Male overview
testes
epididymis
ductus deferens
tip of penis

urethra
Accessory glands
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Seminal vesicles, prostate gland, bulbourethral
gland
Sperm production
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Formed in seminiferous tubules
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Travel along epididymis (6 meters - 4 days travel)
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Stored (up to 1 month) in epididymis (motile)
Sertoli cells and epididymis secrete hormones
and nutrients
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(non-motile)
Accessory glands
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Semen = sperm plus secretions
1. Seminal vesicles
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60% semen volume
Yellow fluid (pH 3 - 7)
Fructose and citric acid (nutrients)
Prostaglandins (decreasing cervical mucus, reverse
peristalsis of uterus and fallopian tubes)
Accessory glands
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2. Prostate gland
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30% semen volume
Alkaline fluid (neutralizes citric acid and female
vaginal acidity)
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3. Bulbourethral gland
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Alkaline solution (neutralizes acid urine in male
urethra)
Mature sperm
Spermatogenesis regulation
• GnRH released
• LH and FSH release
• FSH works on Sertoli cells
(sustentacular) causing ABP release
• LH causes release of testosterone
• Spermatogenesis is enhanced
• Inhibin released by Sertoli cells
inhibits release of GnRH
Hormonal effects
1. Increase in growth of genitalia
2. Facial hair, axillary hair (chest, pubis,
back)
3. Baldness
4. Voice: enlargement of the larynx
5. Skin: increase in thickness, oil glands
6. Muscle: increase in growth
7. Bone: increase in thickness
Sperm delivery
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Erection - parasympathetic reflex from
sacral region of spinal cord
Relaxes smooth muscle
Arteries dilate, simultaneous constriction of
veins
Blood rushes into erectile tissue
Inhibitors: alcohol inhibits higher brain
function
Sperm delivery
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Ejaculation: sympathetic control. Nerve
discharge from nerves on L1 and L2
Result
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contraction of reproductive ducts and
accessory glands
bladder sphincter muscle contract
smooth muscles surrounding penis contraction