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1
Chapter 21Reproductive
System
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Reproduction
• Asexual reproduction
– One parent produces genetically identical
offspring
– Very rapid reproduction
– Can proceed via
– Budding
– Fission
– Fragmentation/regeneration
Reproduction
• Sexual reproduction involves thefusion of gametes from two parents
–Resulting in genetic variation amongoffspring
–Increased reproductive success inchanging environments
• Some organisms can reproduce
–Asexually or
–Sexually
Eggs
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Human Reproduction
• Both sexes in humans have
– A set of gonads (testes or ovaries) where
gametes (sperm or eggs) are produced
– Ducts for gamete transport
– Structures for copulation
The Male Reproductive System
urinary bladder
vas deferens
pubic bone
urethra
penis
glans penis
foreskin
scrotum
seminal vesicle
ureter (cut)
ejaculatory duct
prostate gland
bulbourethral gland
anus
epididymis
testis
vas deferens
erectile tissue
of penis
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21.1 Male Reproductive System
• Genital Tract
– Sperm are produced by seminiferous tubules of testes
– Undergo maturation in the epididymis
– Sperm pass through vas deferens where products are
secreted by glands that contribute to semen
• Seminal vesicles
• Prostate gland
• Bulbourethral gland
– Semen is alkaline and contains fructose
– Over 400 million sperm cells in one ejaculation
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21.1 Male Reproductive System
• Male Gonads, the Testes
– Produce sperm and hormones
– Located outside of the body cavity in scrotum
• Internal body temperature is too high for sperm production
A Testis
• Spermatogenesis occurs
in the seminiferous
tubules
• Interstitial cells produce
testosterone
vas deferens
epididymis
testis
lobule
scrotal sac
uncoiled
seminiferous
tubule
a. Testis, cut to show lobules
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A Sperm Cell
• Three Main Parts
– Head
• The acrosome contains
enzymes needed to
penetrate an egg
– Middle Piece
• Many mitochondria
– Tail
• Flagellum
acrosome
head
middle piece
tail
end piece
d.
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140 !m
tails of sperm in lumen of seminiferous tubule
Sertoli cell
vas deferens
epididymis
testis
lobule
scrotal sac
MEIOSIS I MEIOSIS II
acrosome
head
middle piece
tail
end piece
b. Seminiferous tubules
c. Spermatogenesis d.
100 !m
uncoiled
seminiferous
tubule
MITOSIS
spermatogonium
(diploid)
primary
spermatocyte
secondary
spermatocyte
early
spermatid
late
spermatid
immature sperm
(haploid)
a. Testis, cut to show lobules
nucleus of
Sertoli cell
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interstitial cell
b(top): © CNRI/Photo Researchers, Inc. b(bottom): © Ed Reschke
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MEIOSIS I MEIOSIS IIMITOSIS
spermatogonium
(diploid)
primary
spermatocyte
secondary
spermatocyte
early
spermatid
late
spermatid
sperm
(haploid)
Spermatogenesis21.2 Female Reproductive System
vagina
uterus
ovaryoviduct
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cervix
21.2 Female Reproductive System
oviduct
ovary
uterus
urinary bladder
pubic bone
urethra
glans clitoris
labium minora
labium majora
vaginal orifice
fimbriae
cervix
rectum
vagina
anus
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21.2 Female Reproductive System
• Oogenesis
– production of an egg (oocyte)
– begins before birth—diploid cells start meiosis
and stop
– each month about one primary oocyte
resumes meiosis
– a secondary oocyte arrested at metaphase
of meiosis II is ovulated
– meiosis of the ovum is completed after
fertilization (in oviduct)
2n
2n
Differentiationand onset of
Meiosis I
Diploid cellin embryo
Firstpolar body
n
n
Completionof Meiosis I
and onset ofMeiosis II
n
n
Entry of spermtriggers completion
of Meiosis II
Secondpolar body
Ovum
(haploid) Sperm
Corpusluteum
Ovulation Ruptured follicle
Mature follicle
Growingfollicle
Ovary
(arrested in prophaseof Meiosis I; presentat birth)
Primary oocyte
Secondary oocyte
(arrested at meta-phase of Meiosis II;released from ovary)
Ovarian Cycle
Oogenesis Spermatogenesis
Primaryoocyte
Primaryspermatocyte2n 2n
n
nn n
nnnn
n
Secondaryspermatocyte
Secondaryoocyte
Polar body
Sperm
Once permonth
Fertilization
Polar body
ZygoteOvum 2nn
n
Hormonal Control of the Ovaries
• The hypothalamus,
anterior pituitary and
ovaries all function to
control female
hormone levels. Like
other hormones,
female hormones are
regulated by feedback
mechanisms.
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LH
FSH
GnRH
oocyte
hypothalamus
anterior
pituitary
follicle
estrogen
corpus
luteum
progesterone
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Ovarian and Uterine Cycles
FSH LH
1 3 5 7 9 11 13 15 17 19 21 23 25 27 1Days
Ovarian cycle ovulation
early
corpus luteum
regressing
corpus luteum
maturefollicledeveloping follicle
Follicular Phase Ovulation Luteal Phase
Ov
ari
an
Ev
en
tsH
orm
on
e
Le
ve
lsE
nd
om
etr
ium
1 3 5 7 9 11 13 15 17 19 21 23 25 27 30
Ho
rmo
ne
Le
ve
ls
Menstruation Proliferative Phase Secretory Phase
Days
ovulationUterine cycle
estrogen
menstruation
progesterone
21.3 Female Hormone Levels
• Menstruation
– Arteries that supply the endometrium (uterine lining)
constrict thereby weakening the capillaries
– The endometrium detaches in random patches
– Tissue, blood, and mucus are lost in the menstrual
flow
– Menstruation lasts 3!10 days
21.3 Female Hormone Levels
• Fertilization and Pregnancy
– An embryo begins development in the oviduct
– Implantation occurs when embryo migrates into uterus
– Embryo begins to produce human chorionic
gonadotropin (hCG)
• hCG maintains the corpus luteum to prevent a drop in levels
and estrogen and progesterone
• Pregnancy tests detect hCG
– Later, the placenta will secrete estrogen and
progesterone
– Estrogen and progesterone prevent ovulation and help
to maintain the endometrium
Implantation
oviduct
a.
ovary
embryo(not drawn
to scale)
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21.3 Female Hormone Levels
• Estrogen and Progesterone
– Both have effects other than those in the ovarian and
uterine cycles
– Estrogen
• Maintains female secondary sex characteristics
– Breast development, axillary and pubic hair, subcutaneous fat
deposition
– Wider pelvis
– Progesterone
• Also needed for breast development
21.3 Female Hormone Levels
• Menopause
– Generally occurs between the ages of 45!55
– Ovaries become unresponsive to FSH and LH
– At the onset of menopause, the menstrual cycle
becomes irregular. Other characteristics include hot
flashes, dizziness, headaches, insomnia, and
depression.
– Menopause is complete when menstruation has not
occurred for one year
– Hormone replacement therapy has advantages and
disadvantages
21.5 Disorders of the Reproductive
System
• AIDS (Acquired Immunodeficiency Syndrome)– Caused by HIV (human immunodeficiency virus)
– Transmission
• Sexual Contact
• Intravenous drug use
• Birthing process
• Breast feeding
– Primary host cells are immune cells
– Patients are usually given multiple drugs
• Treatment, not a cure
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21.5 Disorders of the Reproductive
System
• Genital Herpes– Two types of Herpes Simplex Virus
• Type 1: Colds sores and blisters (oral)
• Type 2: Genital herpes
– Symptoms• Tingling, itching occur first
• Then blisters appear (2!20 days later)
• Fever, painful urination, swollen lymph nodes
– Later, the virus lies dormant• May be reactivated by environmental factors
– Infection of newborn babies can occur with serioushealth issues
21.5 Disorders of the Reproductive
System
• Human Papillomaviruses (HPV)
– Cause genital warts
– Some HPV’s can cause cervical cancer
– Early detection of cervical cancer is possible
by means of a Pap smear
– No cure, treatments include removal of the
warts by freezing, burning, acids, or lasers
– A vaccine is available
21.5 Disorders of the Reproductive
System (STDs)
• Hepatitis B
– Hepatitis B Virus
– Highly contagious
• About 50% of infected people have symptoms that include:
fever, headache, nausea, muscle aches, abdominal pain,
jaundice
• Can lead to liver failure
– Vaccination with HBV vaccine can prevent infection
21.5 Disorders of the Reproductive
System (STDs)
• Bacterial Infections
– Treated with antibiotics
• Gonorrhea
• Syphilis
• Chlamydia– More new chlamydial infections diagnosed than any
other STD
– Mild lower urinary tract signs are common!painful
urination, burning, mucus discharge
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21.5 Disorders of the Reproductive
System
• In Males
– Erectile Dysfunction (impotence)
• Inability to produce or maintain an erection
• Causes may include diseases, medications,
alcohol consumption, and psychological factors
• Drugs that increase blood flow to the penis are a
common treatment
21.5 Disorders of the Reproductive
System (Males)
• Disorders of the Prostate
– Benign Prostatic Hyperplasia (BPH)
• Enlargement of the prostate
• May constrict the urethra resulting in bladder or
kidney damage
• Treated with medications and/or surgery
– Prostate Cancer
• Most common diagnosed cancer in American
males
• Treatable if detected early
21.5 Disorders of the Reproductive
System (Males)
• Testicular Cancer
– Most common cancer in males aged 15!35
– Highly treatable if detected early
– Self-examinations are highly recommended
21.5 Disorders of the Reproductive
System (Females)
• Endometriosis
– Presence of endometrial
tissue outside of the uterine
cavity
– Pain, abnormal menstrual
cycles and infertility may
result
– Treatments include pain
management, drugs, and
surgery
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21.5 Disorders of the Reproductive
System (Females)
• Ovarian Cancer
– Typically occurs in women over the age of 40
– 50% five-year survival rate
– Symptoms may not appear until the cancer is
in later stages
– Women who have not had children are at a
higher risk
21.5 Disorders of the Reproductive
System (Females)
• Disorders of Menstruation
– Too little bleeding
– Too much bleeding
– Dysmenorrhea (painful menstruation)
• Half of all women may experience this
– Premenstrual Syndrome (PMS)
• Characteristics include mood swings, headaches,
joint pains, digestive upsets, and sore breasts
21.5 Disorders of the Reproductive
System (Infertility)
• Infertility is the failure to conceive after one year
of regular, unprotected intercourse
– 15% of couples are infertile
• 40% due to male, 40% due to female, 20% due to both
– Causes
• Low sperm count or sperm abnormalities
– Sedentary life style, smoking, alcohol consumption all
contribute
• Body weight in women
– Obesity is linked to ovulation failure
• Pelvic inflammatory disease in women (blocks oviducts)
• Endometriosis
21.5 Disorders of the Reproductive
System (Infertility)
• Assisted Reproductive Technologies (ART)– Artificial Insemination by Donor (AID)
• Sperm are placed in the vagina
• Donor may be the woman’s partner or a donor
– In Vitro Fertilization (IVF)• Immature eggs are harvested and maturity occurs in vitro
• Sperm are added and fertilization takes place
• Embryos are then implanted
– Surrogate Mothers• Embryos from a couple are implanted into another woman
– Gamete Intrafallopian Transfer (GIFT)• Eggs and sperm are placed in the oviducts
– Intracytoplasmic Sperm Injection (ICSI)• A single sperm is injected into an egg and implanted