Transcript Inquiry into Life, Eleventh Edition

Inquiry into Life
Eleventh Edition
Sylvia S. Mader
Chapter 21
Lecture Outline
21-1
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
21.1 The male reproductive system
• Male genital tract
– Includes structures in fig. 21.1 and Table 21.1 on the following
slides
– Sperm produced by seminiferous tubules of testes
– Undergo maturation in the epididymis
• Maturation involves gaining of motility
• The Acrosome is “the cap” portion of the sperm that contains
the enzymes needed to penetrate the egg.
– Sperm pass through vas deferens where products are secreted
by glands that contribute to semen
• Prostate
• Bulbourethral glands
• Seminal vesicles
– Semen is alkaline and contains fructose and prostaglandins
21-2
The male reproductive system
• Fig. 21.1
21-3
Male reproductive organs
• Table 21.1
21-4
The male reproductive system cont’d.
• Orgasm in males
– Penis is the organ of sexual intercourse
• Glans is covered by prepuce (foreskin)
– Circumcision removes foreskin
– Composed of 3 bodies of erectile tissue
– Erection-arteries leading into erectile tissue relax, venous
drainage is compressed- erectile tissue fills with blood
– Erectile dysfunction-erectile tissue fails to fill enough to
compress venous drainage
» Drugs like Viagra increase penile blood flow
• Height of excitation- increased heart rate and respiratory rate,
smooth muscle contractions propel semen through urethra
• Males have refractory period after orgasm
21-5
The male reproductive system cont’d.
• Male gonads, the testes
– Develop in the abdomen, migrate to scrotum
• Crypt orchidism-failure of testes to migrate-infertility
– Extra-abdominal location allows thermoregulation
• Spermatogenesis requires lower temperatures
– Seminiferous tubules
• Located within lobules of testes
• Site of spermatogenesis-newly formed cells move away from outer
walls into lumen and undergo meiosis
• Sperm structure- refer to fig. 21.3 on following slide
• Sertoli cells- nourish developing sperm
– Interstitial cells- between tubules, secrete testosterone
21-6
Testis and sperm
• Fig 21.3
21-7
The male reproductive system cont’d.
• Hormonal regulation in males
– Gonadotropin releasing hormone from the hypothalamus causes
the anterior pituitary to release FSH and LH
• FSH targets seminiferous tubules- stimulates sperm production
• LH stimulates interstitial cells of the testes to produce testosterone
• All are regulated by negative feedback
– Testosterone is responsible for male secondary sex
characteristics
21-8
Hormonal control of the testes
• Fig. 21.4
21-9
21.2 Female reproductive system
• The genital tract
– Ovaries are within the abdominal cavity
• Eggs- ovulated from the surface of the ovary
– Oviducts extend from the ovaries to the uterus
• Not directly attached to ovaries
• Ends of oviducts have fimbriae- sweep the ovulated eggs into the
opening of the oviduct
• Egg migrates along oviduct propelled by cilia
– If not fertilized, only is viable for 24 hours
– Fertilization occurs midway through oviduct
• Zygote enters the uterus, implants in the uterine wall (endometrium)
– Uterus is a thick-walled muscular organ
• Neck of the uterus (cervix) leads into the vagina
21-10
The female reproductive tract
• Fig. 21.5
21-11
Female reproductive organs
• Table 21.2
21-12
Female reproductive system cont’d.
• External genitals
– Collectively called the vulva
• Labia majora- outer skin folds
• Labia minora- inner skin folds
• Glans clitoris- composed of erectile tissue like the penis
– Cleft between labia minora contains the urethra and vestibule of
the vagina
• Vagina may be partially closed by the hymen
• Note that in the female the reproductive and urinary
systems are entirely separate, unlike males
21-13
External genitals of the female
• Fig. 21.6
21-14
Female reproductive system cont’d.
• Orgasm in females
–
–
–
–
Labia minora, vaginal walls,clitoris become engorged
Erection of nipples
Secretion of vaginal fluids, mucus for lubrication
Vagina is the organ of intercourse,clitoris plays an important role
in excitation and orgasm
– Height of excitation- increased heart rate, blood pressure, and
smooth muscle contractions
– Females have no refractory period following orgasm
21-15
21.3 Female hormone levels
• The ovarian cycle
– Many follicles in the cortex of ovary
• Each contains an oocyte
– A female is born with about 2 million follicles, but they decrease
in number to about 400,000 by puberty
• Only about 400 mature throughout life, 1 per month during
reproductive years
– Ovarian cycle consists a sequence of changes
• Primary follicles develop into secondary follicles
• Secondary follicles develop into vesicular follicles
– Vesicular follicle is fluid filled, bulges on ovarian surface
21-16
Female hormone levels cont’d.
• Ovarian cycle con’td.
– Oogenesis is initiated as follicle matures
• Primary oocyte divides producing one haploid secondary oocyte
and one polar body
• Vesicular follicle ruptures and releases the secondary oocyte and
the polar body both enclosed in a membrane- ovulation
– Vesicular follicle turns into a temporary endocrine structure
called a corpus luteum (CL) following ovulation
• If fertilized in the oviduct, the secondary oocyte then undergoes
meiosis II
– One egg and a polar body are produced
– The fertilized egg contains the diploid number of chromosomes
• If no fertilization occurs, the CL degenerates in 10 days
21-17
Female hormone levels cont’d.
• Phases of the ovarian cycle
– Follicular phase-FSH stimulates follicle development
• Mature follicle begins to produce estrogen
• Estrogen feeds back and shuts of FSH-negative feedback
• Estrogen spike stimulates the release of a large amount of GnRH
from hypothalamus
– Leads to an increase in LH production
– Induces ovulation at around the 14th day of a 28 day cycle
– Luteal phase-LH promotes development of the CL
• CL produces progesterone and some estrogen
• As progesterone rises it feeds back and shuts off LH-negative
feedback
– This causes degeneration of the CL
21-18
Ovarian cycle
• Fig. 21.7
21-19
Hormonal control of the ovaries
• Fig. 21.8
21-20
Female hormone levels cont’d.
• The uterine cycle-based on an average 28 day cycle
– Days 1-5 menstrual phase
• Drop in progesterone causes endometrium to break down and
slough off as menstrual flow
– Days 6-13 proliferative phase
• Increased estrogen production by maturing follicle
• Causes proliferation and thickening of the endometrium
– Day 14- ovulation occurs
– Day 15-28 secretory phase
• Progesterone from the CL maintains the thickened endometrium
• Stimulates glandular secretions in endometrium
• If fertilization does not occur, the CL breaks down and progesterone
decreases brings about the menstrual phase
21-21
Female hormone levels
• Fig. 21.9
21-22
Ovarian and uterine cycles
• Table 21.3
21-23
Female hormone levels cont’d.
• Fertilization and pregnancy
– Zygote begins cell divisions while still in the oviduct
– Oviduct narrows to slow passage into the uterus
• Allows the uterus to be fully in secretory phase to support
pregnancy
– Implantation occurs when embryo migrates into uterus
• Embryo at this stage consists of a ball of cells
– Embryo begins to produce human chorionic gonadotropin (HCG)
• Has LH-like activity to maintain CL to keep progesterone supply
– Trophoblast cells of embryo begin development of the placenta
• Will supply fetus with oxygen and nutrients
• Placenta will also produce progesterone and estrogen
21-24
Female hormone levels cont’d.
• Pregnancy cont’d.
– In summary- a source of progesterone is needed to keep the
uterus in secretory phase
• Earliest source is CL
• To maintain the CL the embryo produces HCG to give the placenta
time to develop
• Once the placenta is functional, HCG decreases and the CL
degenerates
• The placenta is now the source of progesterone
– Keeps uterus in secretory phase
– Suppresses the anterior pituitary so no new follicles form
21-25
Implantation
• Fig. 21.10
21-26
Female hormone levels cont’d.
• 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
21-27
Female hormone levels cont’d.
• Menopause
– Generally occurs between the ages of 44-55
– Ovaries become nonresponsive to GnRH
– Perimenopause-time when cycles become irregular
• Can last 10 years
• Hot flashes, dizziness, headaches, insomnia
• Most women experience only mild symptoms or none at all
– Hormone replacement therapy
• New information suggests that disadvantages outweigh advantages
21-28
21.4 Control of reproduction
• Birth control methods
– Abstinence is the most effective!
– Oral contraceptives-contain estrogen and progesterone
• Shut down both LH and FSH so no ovulation
– Intrauterine device-IUD
• Recently new IUD’s have become available
• Alter the environment of uterus so implantation does not occur
– Barrier methods
• Diaphragm- covers the cervix; must be used with spermicide
• Condom-also protects against STD’s; male and female versions
available
– implants and injections-progesterone or combinations of
estrogen and progesterone
• Function like oral contraceptives but more long term
21-29
Control of reproduction cont’d.
• Birth control methods cont’d.
– Natural family planning (Rhythm Method)
• Effectiveness depends upon education and compliance
• Generally about 70% effective
• Refrain from intercourse approximately 3 days before to 3 days after
ovulation
– But ovulation is difficult to predict
– Birth control methods and efficacies are summarized on the
following slide
21-30
Common birth control methods
• Table 21.4
21-31
Control of reproduction cont’d.
• Morning-after pills
– Emergency contraception
– Taken after intercourse has occurred
– Two types, both disrupt uterine environment
• Preven- series of progesterone pills; disrupts normal cycle making
implantation difficult
• RU-486- mifepristone; blocks progesterone receptors in the uterus
so that the endometrium is sloughed off
21-32
Control of reproduction cont’d.
• Infertility-failure to conceive after 1 year of 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- ovulation failure
• Pelvic inflammatory disease in women- blocks oviducts
• Endometriosis-uterine tissues outside the uterus; can block oviducts
21-33
Control of reproduction cont’d.
• Assisted reproductive technologies (ART)
– Artificial insemination by donor (AID)
• Sperm are placed in the vagina
• Donor may be the woman’s partner or from another selected
individual
• Variation- intrauterine insemination (IUI)- uterus is prepared by
administration of fertility drugs and sperm are placed directly in the
uterus
– In vitro fertilization (IVF)
• Immature eggs are harvested and maturity occurs in glassware
• Sperm are added and fertilization takes place
• Embryos are then implanted
21-34
Control of reproduction cont’d.
• ART cont’d.
– Gamete intrafallopian transfer (GIFT)
• Eggs and sperm are harvested and then placed in the oviducts
immediately after they have been combined
– Can also wait until zygotes form and then these are placed in
the oviducts
• 1 step procedure
– Surrogate mothers
• Embryos from a couple are implanted into another woman for
development to occur
– Intracytoplasmic sperm injection (ICSI)
• A single sperm is injected into an egg and then placed in the uterus
or oviduct
21-35
21.5 Sexually transmitted diseases
• AIDS-acquired immunodeficiency syndrome
– Caused by HIV (human immunodeficiency virus)
– Infects helper T lymphocytes
• Helper T’s are necessary for B lymphocytes to make antibodies and
for cytotoxic T lymphocytes to kill virus-infected cells
– Transmitted by sexual contact including vaginal and anal
intercourse, and oral-genital contact
– Sharing of hypodermic needles is also a means of transmission
– Intrauterine transmission is also possible, as well as infection
through breast-feeding
– 38.6 million adults and 3.2 million children are infected worldwide
– Homosexual males are the largest population affected, with
heterosexual females showing the greatest rate of increase
21-36
HIV, the AIDS virus
• Fig. 21.12
21-37
Sexually transmitted diseases cont’d.
• Categories of an HIV infection
– Category A stage- helper T cell count is at least 500 per mm3
• Immune function is still normal
• HIV is replicating rapidly and the helper T population drops
rapidly
• Some people show mild mononucleosis-like symptoms
• HIV test will not yet be positive but the person is contagious
• After a period of time, antibodies against HIV begin to appear
and a blood test will be positive
• As long as the immune system stays ahead of the number of
virus-infected cells, the person has an ability to fight off
infections
21-38
Sexually transmitted diseases cont’d.
• Categories of HIV infection cont’d.
– Category B stage- helper T count is 200-499 per mm3
• Can occur months to years after infection
• Swollen lymph nodes, unexplained fever, night sweats,
cough, diarrhea
• CNS signs also possible- depression, loss of memory
• Secondary infections may begin- commonly thrush, shingles,
herpes simplex
21-39
Sexually transmitted diseases cont’d.
• Categories of HIV infection cont’d.
– Category C- helper T cell count below 200 per mm3
• Patient is extremely thin and weak
• Opportunistic infections
– From decreased immune function
– Pneumocystis carinii pneumonia
– Mycobacterium avium complex
– Toxoplasmosis encephalitis
– Kaposi’s sarcoma
– Cytomegalovirus
• Death results from any of the opportunistic infections
21-40
Sexually transmitted diseases cont’d.
• Treatment for HIV
– “Life cycle” of the virus
• HIV is a retrovirus-enveloped virus with a spike for attachment
• Attaches to a receptor on a helper T cell and enters the cell
– Viral genetic material is released along with the enzyme
reverse transcriptase-reverse transcription occurs
» Directs the synthesis of viral DNA from viral RNA
– Integration-viral enzyme integrase inserts the viral DNA into the
host cell genome
» Directs the synthesis of more viral RNA
– Some RNA is used for synthesis of viral proteins, which are cut
into small pieces by cleavage
– Assembly and budding of new virus particles occurs
21-41
Reproduction of HIV
• Fig. 21.14
21-42
Sexually transmitted diseases cont’d.
•
•
As HIV particles are released, part of the envelope comes from the T cell
membrane, and the spike from proteins encoded by viral genes
Drug therapy
– Highly active antiretroviral therapy (HAART)
• Combination of drugs
– Entry inhibitors
– Reverse transcriptase inhibitors- like AZT
– Integrase inhibitors
– Protease inhibitor
• Can stop progression of infection for long periods in many cases
• No cure, however, because when discontinued the virus
progression continues
21-43
Sexually transmitted diseases cont’d.
• Treatments for HIV cont’d.
– Vaccines
• An effective vaccine should increase B lymphocyte production of
antibodies and stimulate cytotoxic T cells
• Clinical trials of vaccines have not been successful to date
• Some researchers believe a combination of vaccines will be
necessary
21-44
Sexually transmitted diseases cont’d.
• Genital herpes- caused by herpes simplex
– Type 1 generally causes cold sores while type 2 is associated
with genital lesions
• Crossover can occur
– Begins as a tingling or itching sensation
• Followed by development of blisters, swollen lymph nodes, fever,
painful urination
• When blister rupture, painful ulcers develop
– After blisters heal the virus becomes dormant in cell bodies of
sensory neurons
• Stress, menstruation, sunlight, intercourse all may reactivate the
virus
– Babies born during an outbreak may be infected
21-45
Sexually transmitted diseases cont’d.
• Genital warts- human papilloma virus
–
–
–
–
–
Transvaginal infection possible at birth
Flat, raised warts on genitals
Implicated in cancer of the cervix, vulva, vagina, anus, and penis
No cure
Treatment is by topical therapies or surgery
21-46
Sexually transmitted diseases cont’d.
• Hepatitis infections
– Hepatitis B is an STD
• Hepatitis A is transmitted by contaminated water
• Hepatitis C by exposure to infected person’s blood
– Hepatitis B is highly contagious
• Only 50% of infected people have symptoms
• Fever, headache, nausea, muscle aches, abdominal pain, jaundice
• Can lead to liver failure
– Vaccination with HBV vaccine can prevent infection
21-47
Sexually transmitted diseases cont’d.
• Chlamydia
– Caused by bacterium Chlamydia trachomitis
– More new chlamydial infections diagnosed than any other STD
• 5 times as many women as men are diagnosed
• Probably reflects a decrease in males seeking medical attention
– Mild lower urinary tract signs are common-painful urination, burning,
mucus discharge
• Can spread to prostate in men
• Can lead to pelvic inflammatory disease in women-infertility
• Babies born to infected women may develop pneumonia and ocular
infections
– Guidelines for testing general population-women up to 24 years old with
multiple sex partners, history of unprotected sex, bleeding during pelvic
exam
– Treatment- antibiotics
21-48
Chlamydia eye infection
• Fig. 21.16
21-49
Sexually transmitted diseases cont’d.
• Gonorrhea
– Caused by bacterium Neisseria gonorrheoae
– Males- painful urinations, greenish-yellow discharge
– Females-often no symptoms until pelvic inflammatory disease
develops
– Babies born to infected mothers may develop severe eye
infections leading to blindness
• All babies delivered vaginally receive prophylactic treatment with
ocular anitbiotics or silver nitrate
– Treatment for gonorrhea is antibiotic therapy
21-50
Sexually transmitted diseases cont’d.
• Syphilis
– Caused by the bacterium Treponema pallidum
– 3 stages of disease
• Primary stage- hard sore called a chancre indicates point of
infection
• Secondary stage- non-itchy rash, hair loss, gray patches on mucous
membranes
• Tertiary stage- weakening of arterial walls (aneurysms),
psychological disturbances, large ulcers on skin
– Congenital syphilis- crosses placenta and causes fetal blindness
and malformations
– Treatment for syphilis is penicillin
21-51
Syphilis
• Fig. 21.17
21-52
Sexually transmitted diseases cont’d.
• Bacterial vaginosis
– Overgrowth of the bacterium Gardnerella vaginalis
• Can be nonsexual in transmission, but is commonly passed by
asymptomatic males
• Vaginal itching and discharge
• Trichomoniasis
– Caused by the protozoan Trichomonas vaginalis
– Frothy white foul-smelling discharge
21-53