Transcript Nerve activates contraction

PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
The
Reproductive
System
16
PART A
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The Reproductive System
 Purpose is to promote survival of the species
 Gonads—primary sex organs
 Testes in males
 Ovaries in females
 Gonads produce gametes (sex cells) and secrete
hormones
 Sperm—male gametes
 Ova (eggs)—female gametes
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Male Reproductive System Overview
 Testes
 Duct system
 Epididymis
 Ductus (vas) deferens
 Urethra
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Male Reproductive System Overview
 Accessory organs
 Seminal vesicles
 Prostate
 Bulbourethral glands
 External genitalia
 Penis
 Scrotum
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Male Reproductive System
Figure 16.2a
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Male Reproductive System
Figure 16.2b
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Testes
 Function
 Exocrine- sperm producing function
 Endocrine- testosterone producing function
 Suspended in pouch called the scrotum
 Contains testes and epididymis
 Divided by a septum
 Keeps sperm 3 degrees Celsius below body
temperature
 Subject to traumatic injury
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Testes
 Coverings of the testes
 Tunica albuginea—capsule that surrounds each
testis
 Septa—extensions of the capsule that extend into
the testis and divide it into lobules
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Testes
Figure 16.1
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Testes
 Each lobule contains one to four seminiferous
tubules
 Tightly coiled structures
 Function as sperm-forming factories
 Empty sperm into the rete testis (first part of the
duct system)
 Sperm travels through the rete testis to the epididymis
 Interstitial cells in the seminiferous tubules produce
androgens such as testosterone
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Testes
Figure 16.1
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Duct System
 Epididymis
 Ductus (vas) deferens
 Urethra
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Epididymis
 Comma-shaped, tightly coiled tube
 Found on the superior part of the testis and along the
posterior lateral side
 Functions to mature and store sperm cells (at least 20
days)
 during this time, they mature and gain the ability
to swim
 Expels sperm with the contraction of muscles in the
epididymis walls to the vas deferens
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Epididymis
Figure 16.1
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Ductus Deferens (Vas Deferens)
 Carries sperm from the epididymis to the ejaculatory
duct
 Passes through the inguinal canal and over the
bladder
 Moves sperm by peristalsis
 Spermatic cord—ductus deferens, blood vessels, and
nerves in a connective tissue sheath
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Ductus Deferens (Vas Deferens)
Figure 16.1
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Ductus Deferens (Vas Deferens)
 Ends in the ejaculatory duct which unites with the
urethra
 Expanded end is called the ampulla
 Ejaculation—smooth muscle in the walls of the ductus
deferens create peristaltic waves to squeeze sperm
forward
 Vasectomy—cutting of the ductus deferens at the
level of the testes to prevent transportation of sperm
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Urethra
 Extends from the base of the urinary bladder to the tip
of the penis
 Carries both urine and sperm, but not at same time
 Sperm enters from the ejaculatory duct and the
bladder sphincter constricts
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Urethra
 Regions of the urethra
 Prostatic urethra—surrounded by prostate
 Membranous urethra—from prostatic urethra to
penis
 Spongy (penile) urethra—runs the length of the
penis
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Parts of the Urethra
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Urethra
Figure 16.2b
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Accessory Organs
 Seminal vesicles
 Prostate
 Bulbourethral glands
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Accessory Organs
Figure 16.2b
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Seminal Vesicles
 Located at the base of the bladder
 Produces a thick, yellowish secretion (60% of semen)
 Fructose (sugar)
 Vitamin C
 Prostaglandins
 Other substances that nourish and activate sperm
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Accessory Organs
Figure 16.2b
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Prostate
 Doughnut shaped gland
 Encircles the upper part of the urethra
 Secretes a milky fluid
 Helps to activate sperm
 Enters the urethra through several small ducts
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Prostate
Figure 16.2a
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Prostate Gland
 Hypertrophy of Prostate
 Very common
 Makes urination difficult
 Leads to bladder and kidney infections
 Prostatitis
 Inflammation of the prostate
 Single most common reason for a man to
consult a urologist
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Prostate Gland
 Prostatic Cancer
 Third most prevalent cancer
 Most common cancer in men
 Early detection is critical
 PSA test
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Bulbourethral Glands
Figure 16.2a
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Bulbourethral Glands
 Pea-sized gland inferior to the prostate
 Produces a thick, clear mucus
 Cleanses the urethra of acidic urine
 Serves as a lubricant during sexual intercourse
 Secreted into the penile urethra
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Semen
 Mixture of sperm and accessory gland secretions
 Advantages of accessory gland secretions
 Fructose provides energy for sperm cells
 Alkalinity of semen helps neutralize the acidic
environment of vagina
 Semen inhibits bacterial multiplication
 Elements of semen enhance sperm motility
 Amount of ejaculation is about 1 tsp.
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Male Infertility
 Can be caused by obstruction of the duct system
 Hormonal imbalances
 Environmental estrogens
 Pesticides
 Excessive alcohol
 Antibodies made by some men against their own
sperm
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Male Infertility
 First step in treatment is semen analysis
 Sperm count
 Need 20 million per mililiter
 Motility
 Morphology (shape and maturity)
 Semen volume
 Ph
 Fructose content
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Male Infertility
 Infertility- abnormally low ability to produce
 Sterility- complete inability to reproduce
 Oligospermia- decreased sperm count
 Oligospermia can be caused by
 Infection
 Fever
 Radiation
 Malnutrition
 High temperature in testes
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External Genitalia
 Scrotum
 Penis
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External Genitalia
Figure 16.2a
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External Genitalia
 Scrotum
 Divided sac of skin outside the abdomen
 Maintains testes at 3°C lower than normal body
temperature to protect sperm viability
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External Genitalia
 Penis
 Delivers sperm into the female reproductive tract
 Regions of the penis
 Shaft
 Glans penis (enlarged tip)
 Prepuce (foreskin)
 Folded cuff of skin around proximal end
 Often removed by circumcision
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External Genitalia
Figure 16.2a
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External Genitalia
 Internally there are three areas of spongy erectile
tissue around the urethra
 Erections occur when this erectile tissue fills with
blood during sexual excitement
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External Genitalia
Figure 16.1
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Spermatogenesis
 Production of sperm cells
 Begins at puberty and continues throughout life
 Occurs in the seminiferous tubules
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Spermatogenesis
Figure 16.3
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Spermatogenesis
Figure 16.3 (1 of 2)
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Spermatogenesis
Figure 16.3 (2 of 2)
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Spermatogenesis
 Spermatogonia (stem cells) undergo rapid mitosis to
produce more stem cells before puberty
 Follicle-stimulating hormone (FSH) modifies
spermatogonia division
 One cell produced is a stem cell, called a type A
daughter cell
 The other cell produced becomes a primary
spermatocyte, called a type B daughter cell
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Spermatogenesis
 Primary spermatocytes undergo meiosis
 One primary spermatocyte produces four haploid
spermatids
 Spermatids—23 chromosomes (half as much
material as other body cells)
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Human Life Cycle
 Union of a sperm (23 chromosomes) with an egg (23
chromosomes) creates a zygote (2n or 46
chromosomes)
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Human Life Cycle
Figure 16.4
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Spermiogenesis
 Late spermatids are produced with distinct regions
 Head
 Midpiece
 Tail
 Sperm cells result after maturing of spermatids
 Spermatogenesis (entire process, including
spermiogenesis) takes 64 to 72 days
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Structure of a Sperm
Figure 16.5b
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Structure of a Sperm
Figure 16.5a
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Anatomy of a Mature Sperm Cell
 The only human flagellated cell
 Head
 Contains DNA
 Acrosome—“helmet” on the nucleus, similar to a
large lysosome
 Breaks down and releases enzymes to help the
sperm penetrate an egg
 Midpiece
 Wrapped by mitochondria for ATP generation
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Threats to spermatogenesis
 Some common antibiotics can alter sperm
production
 Radiation, lead, certain pesticides, marijuana,
tobacco, and excessive alcohol can cause
production of abnormal sperm
 Two- headed sperm or multi-tailed sperm
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Testosterone Production
 The most important hormone of the testes
 Produced in interstitial cells
 During puberty, luteinizing hormone (LH) activate the
interstitial cells
 In turn, testosterone is produced
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Testosterone Production
 Functions of testosterone
 Stimulates reproductive organ development
 Underlies sex drive
 Causes secondary sex characteristics
 Deepening of voice
 Increased hair growth
 Enlargement of skeletal muscles
 Thickening of bones
 Helps close epiphyseal plate
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Hormonal Control of the Testis
Figure 16.6
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Testosterone Abnormalities
 If testosterone is not produced:
 Secondary sexual characteristics don’t appear
 Reproductive organs remain childlike, called
sexual infantilism
 Effects of castration
 Interstitial cells do not produce testosterone
 Results in decrease in size and function of
reproductive organs and a decreased sex drive
 Sterility occurs because testosterone needed for
final stages of sperm production
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Mechanisms of Disease
 Cryptorchidism
 Undescended testes
 Usually descend two months prior to birth
 Early treatment needed to prevent permanent
sterility
 Testicular Cancer
 Most common between ages 25-35
 Genetic predisposition
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Mechanisms of Disease
 Impotence
 Inability to achieve an erection
 Commonly caused by anxiety or stress
 Temporarily caused by drugs or alcohol
 Can have other medical causes
 Inguinal Hernia
 Intestines push through a weak area of the
abdominal wall and protrudes into the scrotum
 Can be congenital
 Present at birth
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