UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System
Chapter 10: Circulatory System and
Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System
Chapter 14: Reproductive System:
Section 14.1
UNIT B Chapter 14: Reproductive System
Chapter 14: Reproductive System
In this chapter you will learn about the male and female
reproductive systems, the ovarian and uterine cycles, and
disorders of the reproductive systems.
What different events
must occur before
fertilization?
What is the function
of the umbilical cord?
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Cord blood banking. Cord blood can be used to treat diseases such
as leukemia, lymphoma, and other blood and immune system
disorders. After an umbilical cord blood sample is collected, it is
stored in a cord blood bank. There are both private and public banks.
UNIT B Chapter 14: Reproductive System
Section 14.1
14.1 Male Reproductive System
Organisms that carry out sexual reproduction produce
gametes, haploid sex cells that are united during fertilization.
• In the male reproductive system, the sperm are gametes
that are produced in paired testes (male gonads)
o Seminal fluid: a nutrient-rich fluid in which sperm
leave the penis during ejaculation
o Semen: combination of sperm and seminal fluid
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UNIT B Chapter 14: Reproductive System
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Section 14.1
Figure 14.1 The male reproductive system. The testes produce sperm. The seminal
vesicles, the prostate gland, and the bulbourethral glands provide a fluid medium for the
sperm, which move from the vasa deferentia through the ejaculatory ducts to the urethra
in the penis.
UNIT B Chapter 14: Reproductive System
Section 14.1
Genital Tract
• Testes: paired structures that produce sperm and sex hormones
• Epididymides: ducts outside the testes where sperm mature
and are stored
• Vas deferens: stores sperm; empties into an ejaculatory duct
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UNIT B Chapter 14: Reproductive System
• Urethra: connected to the
ejaculatory duct
• Seminal vesicles: contribute
nutrients and fluids to semen
• Prostate gland: contributes
basic solution to semen (sperm
are more viable in a basic
solution)
• Cowper’s glands: secrete a
mucus-rich fluid that helps
lubricate the penis
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Section 14.1
UNIT B Chapter 14: Reproductive System
Section 14.1
• Penis: male organ of sexual intercourse
o Circumcision: surgical removal of the foreskin
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Figure 14.2 Penis anatomy. a. Beneath the skin and the connective tissue lies the
urethra, surrounded by erectile tissue. This tissue expands to form the glans penis,
which in uncircumcised males is partially covered by the foreskin (prepuce).
b. Two other columns of erectile tissue in the penis are located dorsally.
UNIT B Chapter 14: Reproductive System
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Section 14.1
UNIT B Chapter 14: Reproductive System
Section 14.1
Erection and Orgasm in Males
Erection
• Erectile tissue extends
throughout the shaft of the
penis
• Sexual excitement causes the
arteries in the penis to relax
and widen
• Increased blood flow causes
the penis to enlarge and
become erect
Figure 14.2 Penis anatomy. b. Two
other columns of erectile tissue in the
penis are located dorsally.
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UNIT B Chapter 14: Reproductive System
Section 14.1
Ejaculation and Orgasm
• When sexual stimulation intensifies, sperm enter the urethra
from the vasa deferentia and the accessory glands contribute
secretions to the semen
• Rhythmic muscle contractions cause semen to be ejaculated
from the penis
o These contractions are part of male orgasm (climax of
sexual stimulation)
• A refractory period occurs after ejaculation, where sexual
stimulation does not cause an erection
• More than 400 million sperm are expelled in 2 to 6 mL of
semen during ejaculation
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UNIT B Chapter 14: Reproductive System
Section 14.1
Male Gonads, the Testes
Testes
• Lie within the scrotum
• The scrotum helps regulate
testicular temperature by
holding the testes closer or
farther away from the body
• Increases in temperature
may decrease sperm
production
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Figure 14.3 Testis and sperm. a. The lobules
of a testis contain seminiferous tubules.
UNIT B Chapter 14: Reproductive System
Section 14.1
Seminiferous Tubules
• A testis is composed of lobules,
each of which contains tightly
coiled seminiferous tubules
• Intersitial cells that lie between
the tubules secrete male sex
hormones (androgens)
• Seminiferous tubules contain
cells undergoing
spermatogenesis (production of
sperm)
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Figure 14.3 Testis and sperm. b. Light micrographs of a cross section of the seminiferous tubules,
where spermatogenesis occurs. Note the location of interstitial cells in clumps among the seminiferous
tubules.
UNIT B Chapter 14: Reproductive System
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Section 14.1
Figure 14.3 Testis and sperm. a. The lobules of a testis contain seminiferous tubules.
b. Light micrographs of a cross section of the seminiferous tubules, where spermatogenesis
occurs. Note the location of interstitial cells in clumps among the seminiferous tubules.
UNIT B Chapter 14: Reproductive System
Section 14.1
Spermatogenesis
• Occurs in the walls of the seminiferous tubules
• Spermatogonia become primary spermatocytes that
undergo meiosis I to produce secondary spermatocytes
• Secondary spermatocytes undergo meiosis II to produce
four haploid spermatids
• Spermatids differentiate into sperm
• Sertoli cells support, nourish, and regulate the
spermatogenic cells
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UNIT B Chapter 14: Reproductive System
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Figure 14.3 Testis and sperm. c. Diagrammatic representation of
spermatogenesis, which occurs in the walls of the tubules.
Section 14.1
UNIT B Chapter 14: Reproductive System
Section 14.1
Sperm
• Mature sperm (spermatozoa) have a
head, middle piece, and a tail
• Mitochondria in the middle piece is
the site of ATP production for the
movement of the tail
• The acrosome is a cap that stores
enzymes needed to penetrate the egg
• The nucleus of the sperm has the
male’s DNA as 23 chromosomes
• Sperm usually do not live more than
48 hours in the female genital tract
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Figure 14.3 Testis and sperm. d. A sperm has a head, a
middle piece, tail, and an end piece. The nucleus is in the
head, which is capped by the enzyme-containing acrosome.
UNIT B Chapter 14: Reproductive System
Section 14.1
Hormonal Regulation in Males
Hypothalamus controls secretions of the pituitary gland by
secreting gonadotropin-releasing hormone (GnRH).
• GnRH: stimulates the pituitary gland to release folliclestimulating hormone (FSH) and luteinizing hormone
(LH)
o FSH: promotes sperm production in the seminiferous
tubules (which secrete inhibin, a hormone which inhibits
FSH synthesis)
o LH: also called interstitial-cell-stimulating hormone
(ICSH) because it promotes the production of
testosterone by interstitial cells
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UNIT B Chapter 14: Reproductive System
Figure 14.4 Hormonal control of
testes. GnRH stimulates the
anterior pituitary to produce FSH
and LH. FSH stimulates the testes
to produce sperm, and LH
stimulates the testes to produce
testosterone. Testosterone from
interstitial cells and inhibin from
the seminiferous tubules exert
negative feedback control over the
hypothalamus and the anterior
pituitary, and this ultimately
regulates the level of testosterone
in the blood.
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Section 14.1
UNIT B Chapter 14: Reproductive System
Section 14.1
Testosterone
• The main sex hormone in males
• Essential for normal development and functioning of
male reproductive structures
• Maintains male secondary sex characteristics that develop
at puberty (body hair, deeper voices, greater muscular
development)
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UNIT B Chapter 14: Reproductive System
Check Your Progress
1. Compare the functions of the seminiferous tubules,
interstitial cells, epididymis, vasa deferentia, and
urethra.
2. List the three glands that add secretions to semen.
3. Explain the roles of GnRH, FSH, ICSH and
testosterone in male reproduction.
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Section 14.1
UNIT B Chapter 14: Reproductive System
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Section 14.1
UNIT B Chapter 14: Reproductive System
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Section 14.1
UNIT B Chapter 14: Reproductive System
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Section 14.1
UNIT B Chapter 14: Reproductive System
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Section 14.1