Bài giảng Biology 25: Human Biology - Chapter 16 & 17

Sexual Reproduction Sexual Reproduction: Only organ system that is not essential for individual survival. Continuation of species. Gamete formation (eggs and sperm) cells. Homeostatic Role: Maintains secondary sexual characteristics.

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Chapter 16 & Chapter 17Biology 25: Human BiologyProf. GonsalvesLos Angeles City CollegeBased on Mader’s Human Biology,7th edition and Fox’s 8th ed PowerpointsSexual Reproduction Sexual Reproduction: Only organ system that is not essential for individual survival.Continuation of species.Gamete formation (eggs and sperm) cells.Homeostatic Role:Maintains secondary sexual characteristics.Sexual Reproduction: The most common type of animal reproduction.Occurs through the fusion of gametes (sperm and egg).Male: Produces sperm cells. Small and motile, propels itself by whiplike flagellum.Female: Produces eggs (ova). Large and nonmotile.Zygote: Egg cell fertilized by a sperm cell.Fertilization: Creation of zygotes by fusion of ova and sperm cells. Two types:Internal Fertilization: Gametes fuse inside the female’s body. Usually requires copulation (intercourse) in which male delivers sperm directly into body of female. Practiced by most terrestrial animals, aquatic reptiles, birds, and mammals.Sexual ReproductionExternal Fertilization: Gametes fuse outside the female’s body. Mating partners release eggs and sperm simultaneously into the water. Practiced by most aquatic animals: fish, amphibians. Many eggs are lost and eaten by predators. Therefore, many must be made and released for a few to survive.Hermaphroditism: A single individual produces both sperm and eggs.Some such as the tapeworm are capable of self-fertilization.Others (e.g.: earthworm) must mate with other animals.In some species self-fertilization is prevented by development of testis and ovaries at different times.Used by “solitary” animals.Reproductive System of HumansReproductive Functions of Male:Produces spermDelivers sperm to female reproductive tractAll of these processes are regulated and coordinated by hormones secreted by:HypothalamusPituitary gland (anterior portion)Testes (Sing. Testis)Front View of Male Reproductive SystemMajor Organs of Male Reproductive System:Testes: Paired male gonads.Produce sperm through spermatogenesis, which produces four sperm cells of equal size.Spermatogenesis occurs in a vast system of hollow tubes called seminiferous tubules.Each mature sperm has a head, a midpiece, and a flagellum.Sperm head has an acrosome, which produces enzymes that help it penetrate the egg.Human sperm cannot develop at body temperature. Testicles descend from abdominal cavity into scrotum, a skin covered sac, about two months before birth.Undescended testicles (cryptorchidism) may cause infertility.Spermatogenesis Occurs in Seminiferous Tubules of TestesReproductive System of HumansMajor Organs of Male Reproductive System:Epididymus:Large coiled tube (23 ft long) that surrounds testes.Stores sperm while they develop fertilizing ability and motility (about 20 days).During ejaculation, sperm cells are propelled from epididymus.Vas Deferens:Long muscular ducts from scrotum to back of bladder. During ejaculation, the sperm pass from epididymus into these two ducts.Vasectomy: Each vas deferens is cut to prevent sperm from entering urethra.Reproductive System of HumansMajor Organs of Male Reproductive System:Ejaculatory Duct:Short duct after two vas deferens ducts unite.Urethra:Deliver sperm to the exterior.In males, urine and sperm pass through the urethra.Females have a separate urethra from the reproductive system. Reproductive System of Humans Major Organs of Male Reproductive System: Accessory Glands: Produce semen.Functions of semen:Activate sperm cellsProvide nutrients for motilityCounteract acidity of vagina and male urethraStimulate contractions of female reproductive tractAntimicrobial actionEjaculation volume 4 to 5 ml.One ejaculation has 50-500 million sperm cellsSperm cells account for less than 5% of semen volume.Secretions from 3 different accessory glands make up the rest of the volume: Seminal vesicles (2), prostate, and bulbourethral glands (2).Major Organs of Male Reproductive System:Accessory Glands:A. Seminal vesicles (2): Secrete fluid that nourishes sperm.Contribute about 60% of semen volume.Thick, clear, alkaline fluid.Contains:Fructose: Provides energy for sperm motility.Prostaglandins: Stimulate smooth muscle contractions of female and male reproductive tracts.Fibrinogen: Forms temporary clot in vagina.Sperm cells become highly motile when mixed with this fluid.Accessory Glands:B. Prostate gland: Produces a thin milky secretion.Largest of semen secreting glands.Contributes 30% of semen volume.Produces an antibiotic that may prevent urinary tract infections in men.Benign (noncancerous) prostate enlargement is common among older men.50% of men over 40.Almost all men over 70.Prostate cancer is the second leading cause of cancer and cancer deaths in men. Over 330,000 new cases/year and 40,000 deaths. Average age at diagnosis: 72Detected by blood test or digital rectal exam.Treated surgically or with drugs to reduce prostate size or activity.Benign Prostate Enlargement Usually Procedes Prostate CancerNormal prostate is 2 to 3 cm in diameterMajor Organs of Male Reproductive System:Accesory Glands:C. Bulbourethral glands (2): Release a mucous secretion that lubricates penis and facilitates its entry into vagina.Pair of small glands below the prostate.Contribute 5-10% of semen volume.Before ejaculation secrete a clear mucus that neutralizes acid from remaining urine in urethra.Bulbourethral fluid also carries some sperm that is released before ejaculation. One cause of high failure rate of withdrawal method.Major Organs of Male Reproductive System:Penis: Copulatory organ that delivers sperm to female body.Composed of three cylinders of erectile tissue.During sexual arousal, the penis fills with blood from the arteries.Erection is essential for penetration.Impotence is the inability to maintain an erection.May be caused by alcohol, drugs, illness, and/or emotional problems.Viagra acts by relaxing smooth muscle of penis blood vessels, allowing blood to enter erectile tissue.Penis structure:Shaft: Long cylinder with thick skin.Glans: Enlarged tip of penis. Thin skin, covered by prepuce or foreskin.Reproductive System of HumansReproductive Functions of Female:Produces eggs (ova)Receives spermIncubates and nourishes the embryo and fetusGives birthProduces milk for youngAll of these processes are regulated and coordinated by hormones secreted by:HypothalamusPituitary gland (anterior portion)OvariesReproductive System of HumansMajor Organs of Female Reproductive System:Ovaries: Produce ova (oogenesis) and sex hormones.Size and shape of large almonds.Located close to lateral walls of pelvic cavity and held in place by connective tissue.Mainly connective tissue containing scattered eggs (ova) in different stages of development.Follicles: A single egg with surrounding cells that nourish and protect it.Women are born with all of their follicles (40,000 to 400,000). Only a fraction of follicles release eggs during a woman’s reproductive life. Female Reproductive System:Ovulation & Oogenesis: After puberty, each month one immature egg (oocyte), is released from ovary. Each follicle contains a primary oocyte, arrested in prophase I of meiosis.Pituitary hormones FSH (follicle stimulating hormone) and LH (luteinizing hormone) cause a follicle to enlarge and complete meiosis I.One large cell (secondary oocyte) and a tiny cell (polar body) are produced.LH (luteinizing hormone) causes the secondary oocyte to be released by the ovary during ovulation.Oocyte will not finish meiotic division, until fertilized.In the end, one large ovum (egg) and 3 small polar bodies are made from oogenesis.Oogenesis and Ovary StructureMajor Organs of Female Reproductive System:Oviducts (Fallopian Tubes): Transport the egg from the ovary to the uterus.Peristalsis of smooth muscle in oviduct and beating of cilia, help the egg move along.Fertilization occurs in the first third of oviduct.Scarring of oviducts is a common consequence of sexually transmitted diseases: chlamydia and gonorrhea.Ectopic Pregnancy: Fertilized egg does not reach the uterus. Usually starts to develop in oviduct.Usually due to a blocked oviduct.Occurs in 1% of all pregnancies in the U.S. Must be surgically removed. May cause death and severe hemorrhage. Ectopic Pregnancy of TwinsEctopic pregnancies occur in about 1% of pregnancies in U.S.and usually require surgical removal of embryos.Reproductive System of HumansMajor Organs of Female Reproductive System:Uterus: Incubates the embryo/fetus.Size of a fist, in center of pelvic cavity.Oviducts open into upper corners of uterus.Has thick walls of smooth muscle (myometrium) responsible for uterine contractions and cramps.Endometrium: Inner mucous lining, which thickens each month in preparation for pregnancy.If fertilization does not occur, endometrium breaks down and is discharged during menstruation.If fertilization occurs, the egg implants in the endometrium which supports its growth until the placenta develops.The Uterus Incubates and Nourishes the FetusReproductive System of HumansMajor Organs of Female Reproductive System:Cervix: Lower portion of the uterus, which projects into the vagina.Pap smear: Examination of cervical tissue to detect abnormalities. Recommended yearly.Cervical cancer: Most cases caused by a viral infection with human papillomavirus.Women are infected through intercourse with asymptomatic male.Takes about 20 to 30 years to develop.Men don’t appear to be affected.Reproductive System of HumansMajor Organs of Female Reproductive System:Vagina: Thin walled, muscular chamber.Receives the sperm and penisAcid pH kills bacteria and sperm cellsPart of birth canalVulva: External structures.Clitoris: Equivalent to male penis.Labia minora: Skin folds that border vaginal opening.Labia majora: Protect entire genital region.Hymen: Ring of tissue that forms a border around vaginal entrance. No known function.Bartholin’s gland: Secrete lubricating fluid during sexual arousal.Breasts: LactationFemale Hormones Controlling Reproduction Follicle Stimulating Hormone (FSH)Secreted by pituitary glandStimulates growth of ovarian follicleLuteinizing Hormone (LH)Secreted by pituitary glandStimulates growth of follicle and completion of meiosis IInduces ovulation Promotes development of corpus luteum and hormone secretion. EstrogenSecreted by ovarian follicleLow levels inhibit FSH and LH secretionHigh levels stimulate FSH and LH secretionPromotes growth of endometriumProgesterone and EstrogenSecreted by corpus luteumMaintain endometrium, sharp drop causes menstruationHigh levels inhibit inhibit FSH and LH secretionFemale Menstrual Cycle: Approximately 28 days.Menstruation: Day 1 of cycle. Walls of endometrium break down.Caused by falling levels of progesterone and estrogen.Lasts 3 to 7 days.Pre-Ovulatory phase: Starts around day 5 of cycle.Rising estrogen levels cause the endometrium to start thickening.Ovulation: Occurs around day 14 of cycle.FSH stimulates growth of ovarian follicle.LH causes follicle to finish meiosis I (secondary oocyte) and to be released by ovary.Corpus luteum: Starts to secrete estrogen and progesterone.Post-ovulatory Phase: Starts around day 15.Endometrium continues to grow in response to rising estrogen and progesterone.If no fertilization occurs, corpus luteum degenerates and menstruation occurs.If fertilization occurs, embryo maintains corpus luteum.Stages of Female Reproductive Cycle Different Contraceptive Methods1. Prevent Release of Gametes: Birth control pill (combination): Prevents ovulation 2. Prevent Fertilization Vasectomy: Male sterilization Tubal ligation: Female sterilization Minipill: Progestin only, blocks cervical opening Norplant implant: Releases progestin for 5 years Rhythm (calendar): Avoid intercourse around ovulation Withdrawal: Remove penis before ejaculation Condom: Latex or sheepskin barrier Diaphragm, cervical cap: Block cervical opening Spermicide: Kill sperm cells3. Prevent Implantion Intrauterine device (IUD) Morning after pills Effectiveness of Methods of ContraceptionEffectiveness of Methods of ContraceptionCharacteristics of all virusesAcellular infectious agentsObligate intracellular parasitesPossess either DNA or RNA, never bothReplication is directed by viral nucleic acid within a cellDo not divide by binary fission or mitosisLack genes and enzymes necessary for energy productionDepend on host cell ribosomes, enzymes, and nutrients for protein productionUnique Characteristics of HIVRetrovirus: Unique enzyme reverse transcriptase, converts viral RNA into DNA.Genetic material: 2 strands of RNA.Integrase: Inserts viral DNA into host DNA.Protease: Processes viral proteins. Essential for maturation.Envelope with glycoproteins: Viral capsid is covered by envelope derived from host cell membrane. Envelope contains a glycoprotein (gp120) which attaches to CD4 receptor on host cell membrane.Coreceptors: Required for HIV infection. CXCR4 and CCR5.Structure of the Human Immunodeficiency Virus HIV is a RetrovirusLife Cycle of HIV1. Attachment: Virus binds to surface molecule (CD4) of T cells and macrophages.Coreceptors: Required for HIV infection. CXCR4 and CCR5 mutants are resistant to infection.2. Fusion: Viral envelope fuses with cell membrane, releasing contents into the cell.3. Reverse Transcription: Viral RNA is converted into DNA by unique enzyme reverse transcriptase. Reverse transcriptase RNA ---------------------> DNA Reverse transcriptase is the target of several HIV drugs: AZT, ddI, and ddC.HIV Life Cycle: Reverse Transcriptase Converts RNA into DNALife Cycle of HIV4. Integration: Viral DNA is inserted into host cell chromosome by unique enzyme integrase. Integrated viral DNA may remain latent for years and is called a provirus.5. Replication: Viral DNA is transcribed and RNA is translated, making viral proteins. Viral genome is replicated.6. Assembly: New viruses are made.7. Release: New viruses bud through the cell membrane. Course of HIV InfectionDefinition of AIDSAIDS is a syndrome: A collection of several diseases and symptoms that differ from one individual to another, but point to severe immunosuppression.HIV Antibody positive and one of the following (partial list):Kaposi’s sarcomaPneumocystis carinii pneumoniaHIV dementianon-Hodgkin’s B cell lymphomaYeast infection of esophagus, trachea, or lungMultiple bacterial infections in children <13 yearsTuberculosis of the lung*Recurrent pneumonia*Invasive cervical carcinoma*All HIV+ persons with <200 CD4+ cells/ul**Added January 1, 1993. AIDS Associated Disease Categories1. Gastrointestinal: Cause most of illness and death of late AIDS. Symptoms:DiarrheaWasting (extreme weight loss)Abdominal painInfections of the mouth and esophagus. Pathogens: Candida albicans, cytomegalovirus, Microsporidia, and Cryptosporidia.African AIDS patient with slim diseaseSource: Tropical Medicine and Parasitology, 1997Opportunistic Oral Yeast Infection by Candida albicans in an AIDS Patient Source: Atlas of Clinical Oral Pathology, 1999AIDS Associated Disease Categories2. Respiratory: 70% of AIDS patients develop serious respiratory problems.Partial list of respiratory problems associated with AIDS: BronchitisPneumoniaTuberculosisLung cancerSinusitisPneumonitisChest X-Ray of AIDS Patient with TuberculosisAIDS Associated Disease Categories3. Neurological: Opportunistic diseases and tumors of central nervous system. Symptoms many include: Headaches, peripheral nerve problems, and AIDS dementia complex (Memory loss, motor problems, difficulty concentration, and paralysis).AIDS Associated Disease Categories4. Skin Disorders: 90% of AIDS patients develop skin or mucous membrane disorders.Kaposi’s sarcoma1/3 male AIDS patients develop KSMost common type of cancer in AIDS patientsHerpes zoster (shingles)Herpes simplexThrushInvasive cervical carcinoma5. Eye Infections: 50-75% patients develop eye conditions.CMV retinitisConjunctivitisDry eye syndromeExtensive tumor lesions of Kaposis’s sarcoma in AIDS patient.Source: AIDS, 1997Chronic Herpes Simplex infection with lesions on tongue and lips.Source: Atlas of Clinical Oral Pathology, 1999.Non-Hodgkin’s Lymphoma & ascites in AIDS patientSource: Tropical Medicine and Parasitology, 1997Drugs Against HIVReverse Transcriptase Inhibitors: Competitive enzyme inhibitors. Example: AZT, ddI, ddC.Protease Inhibitors: Inhibit the viral proteases. Prevent viral maturation.Problem with individual drug treatments: Resistance.Drug Cocktails: A combination of:One or two reverse transcriptase inhibitorsOne or two protease inhibitors.Drug cocktails have been very effective in suppressing HIV replication and prolonging the life of HIV infected individuals, but long term effectiveness is not clear. Herpes Simplex 1 & 2Characteristics: Herpes Simplex 1 (Oral Herpes): Recurring painful blister lesions that form mainly on lips, but may be found in other areas of body. In immunocompromised patients may have extensive lesions on tongue and inside mouth.Herpes Simplex 2 (Genital Herpes): Recurring painful blister lesions in genital and/or rectal areas.Pathogens: Human Herpes Virus 1: Oral Herpes.Human Herpes Virus 2: Genital Herpes. Reservoir: Humans. Transmission: Kissing, touching lesions, sexual contact.Oral Herpes: Recurrent Herpes LabialisLess than 1 day witherythema and burningSame patient 24 h later with multiplefluid filled vesicles and erythemaSource: Atlas of Clinical Oral Pathology, 1999.Recurrent Herpes Labialis: Bilateral vesicles on upper and lower lips.Source: Atlas of Clinical Oral Pathology, 1999.Oral Herpes: Recurrent Herpes LabialisChronic Herpes Simplex infection with lesions on tongue and lips.Source: Atlas of Clinical Oral Pathology, 1999.Oral Herpes: Chronic Atypical Lesions Herpes simplex 2 infection with fluid filled vesicles on penis.Source: Mike Remington, University of Washington Viral Disease ClinicGenital HerpesAcyclovir resistant peri-rectal HSV2 infection in HIV infected male.Source: AIDS, 1997Genital Herpes Herpes Simplex 1 & 2Incubation period: Several days to weeks. May be asymptomatic.Epidemiology : Millions cases/year in U.S.Oral Herpes: Up to 70% of population is infected. Many have no symptoms.Genital Herpes: Up to 20% of population is infected. Many have no symptoms. Others have recurring lesions several times a year.Treatment and Prevention: No cure. Infection is for life. Antiviral medications (acyclovir) decrease frequency and severity of outbreaks. Women with genital herpes should deliver by cesarean section to avoid infecting newborn. Neonatal herpes is very serious and can be deadly. ChlamydiaCharacteristics: Painful urination, watery discharge, salpingitis, and pelvic inflammation in women. Symptoms may be mild or absent, especially in women. Common cause of sterility in both men and women. Newborns may develop eye infections and pneumonia. Pathogens: Chlamydia trachomatis.Reservoir: Humans. Transmission: Direct sexual contact or mother to infant transmission during childbirth.Incubation period: 2 to 3 weeks. May be asymptomatic.Epidemiology : Up to 1 million new cases/year in U.S. Control: Use of condoms, avoid sexual contact with infected individuals. Prophylactic treatment of contacts and pregnant women. Treatment: Antibiotics.Both Chlamydia and Neisseria gonorrhea Cause SalpingitisChlamydia Infections: Inflammation of eyelidSource: Microbiology Perspectives, 1999GonorrheaCharacteristics: Acute infection of urethra, anus, vagina, cervix, and fallopian tubes. Yellow foul discharge (more common in men). Causes pelvic inflammatory disease (PID) in women. Major cause of infertility in both men and women. May also result in throat and eye infections. In a large percentage of cases, symptoms are mild or absent.Pathogens: Neisseria gonnorrhoea (bacterium).Transmission: Direct sexual or mucous membrane contact. Mother to infant transmission during childbirth.Incubation period: 2 to 7 days. Typical discharge in male with gonorrhea.Source: Tropical Medicine and Parasitology, 1995Gonorrhea: Acute Ur
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