Chapter 28: The Reproductive System-Male The Reproductive System Gonads: –organs that produce...
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Transcript of Chapter 28: The Reproductive System-Male The Reproductive System Gonads: –organs that produce...
![Page 1: Chapter 28: The Reproductive System-Male The Reproductive System Gonads: –organs that produce gametes and hormones Ducts: –receive and transport gametes.](https://reader033.fdocuments.in/reader033/viewer/2022042504/56649e5e5503460f94b57cbb/html5/thumbnails/1.jpg)
Chapter 28: The Reproductive System-
Male
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The Reproductive System
• Gonads:– organs that produce gametes and hormones
• Ducts:– receive and transport gametes
• Accessory glands:– secrete fluids into ducts
• Perineal structures:– collectively known as external
genitalia
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Male & Female Reproductive Systems
• Are functionally different• Female produces 1 gamete per month:
– retains and nurtures zygote
• Male disseminates large quantities of gametes:– produces 1/2 billion sperm per day
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The Male Reproductive System
• Testes or male gonads:– secrete male sex hormones (androgens)– produce male gametes (spermatozoa or
sperm)• Emission:
– mature spermatozoa move along duct system
• Semen:– sperm mixed with accessory gland
secretions• Ejaculation:
– semen expelled from body
![Page 5: Chapter 28: The Reproductive System-Male The Reproductive System Gonads: –organs that produce gametes and hormones Ducts: –receive and transport gametes.](https://reader033.fdocuments.in/reader033/viewer/2022042504/56649e5e5503460f94b57cbb/html5/thumbnails/5.jpg)
What are the components of the male reproductive
system?
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Figure 28–1
The Male Reproductive System
Pathway of Spermatozoa • Testis• Epididymis• Ductus deferens (vas deferens)• Ejaculatory duct• Urethra
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Accessory Organs• Secrete fluids into ejaculatory
ducts and urethra:– seminal vesicles– prostate gland– bulbourethral glands
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External Genitalia • Scrotum:
– encloses testes
• Penis:– erectile organ– contains distal portion of urethra
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Testis • Is egg-shaped• 5 cm long, 3 cm wide, 2.5 cm thick• Weighs 10–15 g• Hangs in scrotum
The Scrotum • Is a fleshy pouch • Suspended infer
– ior to perineum• Anterior to anus• Posterior to base
of penis
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The Fetus: Formation of Testes
• Testes form inside body cavity:– are adjacent to kidneysThe Fetus:
Gubernaculum Testis• Is a bundle of
connective tissue fibers• Extends from testis to
pockets of peritoneum• Locks testes in position
(near anterior abdominal wall) as fetus grows
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Structure of the Testes
Figure 28–4
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Structures of Testes• Septa subdivide testis into lobules• Lobules contain about 800 slender
and tightly-coiled seminiferous tubules
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Seminiferous Tubules• Produce sperm• Each is about 80 cm long• Testis contains about 1/2 mile of tightly-
coiled seminiferous tubules• Each forms a loop connected to rete
testis
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The Epididymis
Figure 28–9
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Sperm Maturation• Testes produce physically mature
spermatozoa that can not fertilize an oocyte
• Other parts of reproductive system are responsible for:– functional maturation, nourishment, storage,
and transport • Spermatozoa:
– detach from sustentacular cells– are free in lumen of seminiferous tubule– are functionally immature
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The Epididymis • Is the start of male reproductive
tract• Is a coiled tube almost 7 m long:
– bound to posterior border of testis
3 Functions of the Epididymis1. Monitors and adjusts fluid
produced by seminiferous tubules2. Recycles damaged spermatozoa3. Stores and protects spermatozoa:
– facilitates functional maturation
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Spermatozoa Leaving Epididymis
• Are mature, but remain immobile• To become motile (actively swimming)
and functional spermatozoa undergo capacitation2 Steps in Capacitation
1. Spermatozoa become motile:– when mixed with secretions of seminal
vesicles
2. Spermatozoa become capable of fertilization:
– when exposed to female reproductive tract
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The Ductus/Vas Deferens and Accessory Glands
Figure 28–10a, b
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The Ductus/Vas Deferens and Accessory Glands
Figure 28–10a, e
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The Ductus/Vas Deferens• Also called vas deferens• Can store spermatozoa
for several months:– in state of suspended
animation (low metabolic rates)
• Is 40–45 cm long• Begins at tail of the
epididymis• Ascends through inguinal
canal:– as part of spermatic cord
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The Ejaculatory Duct • Is a short
passageway (2 cm):– at junction of
ampulla and seminal vesicle duct
• Penetrates wall of prostate gland
• Empties into urethra
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The Male Urethra• Is used by urinary
and reproductive systems
• Extends 18–20 cm:– from urinary
bladder to tip of penis• Is divided into 3
regions:– prostatic– membranous – spongy
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4 Major Functions of Male Glands
1. Activating spermatozoa2. Providing nutrients spermatozoa
need for motility
3. Propelling spermatozoa and fluids along reproductive tract:
– mainly by peristaltic contractions
4. Producing buffers:– to counteract acidity of urethral and vaginal
environments
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The Prostate Gland • Is a small, muscular
organ, about 4 cm diameter
• Encircles proximal portion of urethra below urinary bladder
Prostatic Fluid • Is slightly acidic
• Forms 20–30% of semen volume
• Contains antibiotic seminalplasmin
• Is ejected into prostatic urethra:– by peristalsis of
prostate wall
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The Penis
Figure 28–11a, b
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5 Functions of Testosterone1. Stimulates spermatogenesis:
– promoting functional maturation of spermatozoa
2. Affects CNS function:– libido (sexual drive) and related behaviors3. Stimulates metabolism:– especially protein synthesis, blood cell
formation and muscle growth4. Est. male secondary sex characteristics:
– distribution of facial hair– increased muscle mass and body size– characteristic adipose tissue deposits
5. Maintains accessory glands and organs
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Testosterone and Development • Testosterone production:
– begins around seventh week of fetal development– reaches prenatal peak after 6 months
• Secretion of Müllerian inhibiting factor:– by sustentacular cells– leads to regression of Müllerian ducts
• Early surge in testosterone levels:– stimulates differentiation of male duct system and
accessory organs– affects CNS development
• Testosterone programs hypothalamus, controlling:1. GnRH, FSH, and LH secretion2. sexual behaviors3. sexual drive