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Human Reproduction and Development Anatomy of the Male and Female Reproductive Systems Gamete Formation Hormonal Control of Reproduction Conception, Pregnancy, Development, Birth Male Anatomy • External genitalia – Penis and Scrotum • Internal Reproductive Organs – Pair of gonads • Produce gametes (sperm cells) • Produce hormones – Accessory glands • Secret products essential to sperm movement – Set of ducts • Carry sperm and glandular secretions. Male Anatomy • Penis – Composed of 3 cylinders of spongy tissue. – During sexual arousal, tissue fills with blood from the arteries • The increasing pressure seals off the veins that drain the penis – Result = penis engorges with blood = erection – The tip (Glans) is covered by a fold of skin called the foreskin, which may be removed by circumcision • A tradition with religious roots. • No verifiable health or hygienic advantage. Male Anatomy • Scrotum – Sac which contains testes – Regulates temperature of testes by contraction of cremaster muscle. • Cold = contracts – Brings testes close to body to warm up. • Warm = relaxes • Goal = keep testes 3o below normal body temperature. Male Anatomy • Testes – Stored in scrotum • Before birth, testes develop in the abdomen and then migrate down a canal into scrotum around the time of birth. – Sperm producing organ • Made in tightly coiled tubes called seminiferous tubules inside testes • Sperm produced is not fully mature when it leaves testis (not motile yet) – Source of male hormone testosterone • Made by interstitial cells scattered between the seminiferous tubules – Deposits sperm into epididymis 10 Male Anatomy • Epididymis – Coiled tubes – About 6 meters long!! – Posterior to the testis – Stores sperm – Site of further sperm maturation • Gains motility – Contracts during ejaculation, expelling sperm into vas deferens – Sperm can be store here for months • If not ejaculated, will eventually be phagocytized Male Anatomy • Vas Deferens – Muscular tubes that carry sperm from epididymis to ejaculatory duct (and eventually the urethra) • peristalsis – Urethra drains both the excretory system and the reproductive system • Not the case in females Male Anatomy • Ejaculatory Duct – Connects seminal vesicle to urethra – Passes through prostate gland Male Anatomy • Seminal Vesicle – Lies below and behind bladder – Secretes thick, clear fluid into ejaculatory duct • • • • 60% volume of semen (the fluid that is ejaculated) Alkaline – to neutralize acidic pH of vagina Fructose – used for energy by sperm Prostaglandins – chemical messengers which, once in female, stimulate uterine peristalsis to help move semen up the uterus • Proteins – cause semen to coagulate after it is deposited in the female, making it easier for the uterine contractions to move the semen Male Anatomy • Prostate Gland – Doughnut shaped gland which surrounds urethra – Secretes thin milky fluid into urethra • 20% of seminal volume • Liquefy the semen – prevents sperm from clumping together • Alkaline – continues to neutralize acid from residual urine in urethra and natural acidity of vagina Male Anatomy • Cowper’s Gland (Bulbourethral Gland) – Pair of small glands along urethra, below the prostate – Secrete viscous fluid before emission of sperm & semen • Thought to lubricate penis and vagina – Released before ejaculation • Fluid does contain some sperm • One factor in the high failure rate of the “withdrawal method” of birth control. Male Anatomy • Vasectomy – Incision through scrotum – Cut and tie off vas deferens – Sperm is still produced but can’t get out – Phagocytized Male Anatomy Review • Passageway from testes to outside 1. Multiple seminiferous tubules • site of spermatogenesis 2. Single tubed epididymis 3. Vas deferens 4. Seminal vesicle 5. Ejaculatory duct 6. Urethra Fun Facts • For Your Information – Volume of ejaculation = 2.75 ml – pH = 7.2 – 7.6 – 50 – 150 million sperm per ml. – Only a few sperm reach the egg – Average sperm count has decreased from 113 million/ml to 66 million/ml in past 40 years. – Infertility = <20 million/ml • Factors leading to infertility are environmental toxins, estrogens in meat, radiation, pesticides, marijuana, alcohol Labelling Diagram 1. 2. 3. 4. 5. 6. 7. Pubic Bone Seminal Vesicles Rectum Prostate Gland Cowper’s Gland Anus Vas Deferens (sperm duct) 8. Epididymis 9. Testes 10.Urethra 11.Penis 12.Scrotum 13.Head of Penis (Glans) 14.Foreskin 15.Bladder Hormonal Control • Male Reproductive System Control – Testosterone • Primary Function – Stimulate spermatogenesis • Secondary Function – – – – – – – Maturation of testes and penis Sex drive Facial hair Body hair Deeper voice Increased muscle strength Body oil secretion -- acne Hormonal Control • Hypothalamus releases 1. Gonadotropin-Releasing Hormone (GnRH) • Stimulates pituitary to release LH & FSH • Pituitary releases 1. Follicle-Stimulating Hormone (FSH) • Stimulates spermatogenesis by seminiferous tubules 2. Luteinizing hormone (LH) • Stimulates testosterone production by interstitial cells • Indirectly stimulates spermatogenesis because testosterone is required for sperm production. Hormonal Control • LH, FSH, and GnRH concentrations in the blood are controlled by negative feedback systems Testosterone production Spermatogenesis Testosterone production Spermatogenesis Hormonal Control Hormonal Control Female Anatomy • External genitalia - Two sets of labia that surround the clitoris and vaginal opening • Internal Reproductive Organs - A pair of gonads (ovaries) - A system of ducts and chambers to - Conduct the gametes - House the embryo and fetus Internal Organs Internal Organs Female Anatomy • Ovaries – Lie in abdomen, below most of the digestive system – Enclosed in a tough protective capsule – Produces eggs (follicles) – Produces female sex hormones 1. Estrogen 2. Progesterone Female Anatomy Female Anatomy • Follicles – Consists of one egg cell surrounded by layers of follicle cells. • Nourish and protect the developing egg cell – All of the 400,000 follicles a woman will ever have are present at birth. • • Only a few hundred will be released during a woman’s reproductive years One (very rarely 2 or more) follicle matures and releases its egg during each menstrual cycle Female Anatomy • Follicles – Follicle cells release the primary female sex hormone… estrogen. • • Secondary sex characteristics, wider hips, more body fat, Necessary for breast development – At ovulation, the egg “explodes” out of the follicle leaving behind the follicular tissue • • This grows into a solid mass called a Corpus Luteum – Secretes progesterone (necessary for pregnancy) If fertilization does not occur, the corpus luteum disintegrates and a new follicle matures the next month. Female Anatomy • Oviduct – – – Fallopian tube Conducts eggs to the uterus Fertilization occurs here • – – If embryo grows here = ectopic pregnancy The ovary and oviduct don’t actually touch. The egg is released into the abdominal cavity and is “sucked” into the oviduct. • Oviduct has fingers called “fimbrae” and hairs called “cilia” that vibrate and sweep the egg into the tube by swishing body fluids towards itself • These cilia also help move the egg towards the uterus Female Anatomy Female Anatomy • Uterus (womb) – – – – Houses and nurtures the developing fetus Oviducts enter at the top Cervix (opening) at the bottom The lining is called the endometrium • • • • Richly supplied with blood vessels Varies in thickness depending on the stage of the menstrual cycle Controlled by hormones 2 Layers – Basal layer = stable, does not change thickness – Functional layer = changes thickness with menstruation Female Anatomy Female Anatomy • Vagina – – – – – – Birth canal Average = 7.5 cm in length pH = 4-5 Upper end closes at cervix Receives penis during sexual intercourse Elastic to facilitate sexual intercourse and birth Female Anatomy Gametogenesis 1. 2. 3. 4. The walls of the seminiferous tubules consist of diploid spermatogonia, stem cells that are the precursors of sperm. divide by mitosis to produce more spermatogonia The Meiosis of each spermatocyte produces 4 haploid spermatids. These then differentiate into sperm, losing most of their cytoplasm and gaining motility in the process. In epididymis Sperm nourished by sertoli cells (in seminiferous tubules) Whole process takes 70 days Gametogenesis 1. 2. 3. 4. 5. 6. Takes place in ovaries Primary Oogonium develop into oocytes before birth Oocytes complete maturation one at a time & once a month during reproductive years Primary oocyte grows larger and begins meiosis Forms a secondary oocyte and first polar body After fertilization, secondary oocyte completes meiosis and become 1 egg and second polar body. Hormonal Control •Hypothalamus - produces releasing GnRH •Anterior Pituitary – secrete gonadotropic hormones. –FSH - follicle stimulating hormone. –LH - luteinizing hormone. •Ovaries - secrete the female sex hormones. –Estrogen –thickening of uterine lining –Progesterone – matures/maintains uterine lining Hormonal Control • FSH is released from AP –Start the ripening of ovum within follicle • Estrogen is produced by follicle –Development of endometrium for possible pregnancy –Feedback to hypothalamus to inhibit FSH and release LH Hormonal Control • LH surge on day 14 –Stimulates ovulation –Conversion of follicle into corpus luteum • Progesterone production – Continued development of endometrium – Feedback to inhibit release of LH Hormonal Control •If no fertilization – Degeneration of corpus luteum – Drop in hormone level The 4 Phases of Menstruation Female Anatomy • sdfsdfsdf Menstruation 1. Flow Phase (Menstrual Phase) – Start of bleeding marks Day 1 of phase – Shedding of the endometrium (uterine lining) – Average = 4-5 days • Sometimes up to 8 days – Occurs due to low hormone levels Female Anatomy • sdfsdfsdf 1 Menstruation 2. Follicular Phase – Occurs during day 6-13 – Period of repair and thickening of endometrium. Female Anatomy • sdfsdfsdf Menstruation 2. Follicular Phase – Occurs during day 6-13 – Period of repair and thickening of endometrium. – FSH from the pituitary promotes follicle development in the ovary. Female Anatomy • sdfsdfsdf Menstruation 2. Follicular Phase – Occurs during day 6-13 – Period of repair and thickening of endometrium. WHY?? – FSH from the pituitary promotes follicle development in the ovary. – As follicle develops it produces estrogen, • thickening of the uterine lining • LH production increase • FSH production decrease Menstruation FSH Decrease Menstruation 3. Ovulation Phase – LH causes ovulation to occur on day 14. • Secondary oocyte is released from the follicle/ovary. Female Anatomy • sdfsdfsdf Menstruation 4. Luteal Phase – Final preparation of endometrium to receive the fertilized ovum – LH stimulates development of the Corpus Luteum. • causes progesterone levels to increase. Menstruation Menstruation 4. Luteal Phase – Final preparation of endometrium to receive the fertilized ovum – LH stimulates development of the Corpus Luteum. • causes progesterone levels to increase. – Estrogen and progesterone inhibit GnRH, thereby decreasing LH and FSH levels. – This low level of hormones initiates the flow phase. Menstruation Menstruation Menstruation Menopause • The end of a woman’s reproductive years • Between ages of 45 – 55 • Ovaries no longer respond to FSH & LH from AP – Ovaries do not produce estrogen or progesterone • Marked by circulatory irregularities (hot flashes), dizziness, insomnia, sleepiness, depression • Hormone replacement therapy may help. Human Reproduction and Development Fertilization Pregnancy Development Birth Human Reproduction and Development Sperm Human Reproduction and Development 3 Steps of Fertilization 1. Capacitating – Acidic environment of the female reproductive tract causes small pores to open in the acrosome (“enzymeloaded” head) of the sperm 3 Steps of Fertilization 3 Steps of Fertilization 1. Capacitating – Acidic environment of the female reproductive tract causes small pores to open in the acrosome (“enzymeloaded” head) of the sperm 2. Acrosomal reaction – Enzymes released from acrosome digest the outer membrane surrounding the egg cell 3 Steps of Fertilization 3. Fertilization – A single sperm cell fuses with the plasma membrane of ovum – Head passes into the cytoplasm – Electrochemical reaction in egg • Makes membrane impermeable to other sperm Fertilization • Fertilization must occur within a very short window of opportunity. – Egg is only fertile for 12-24 hours – Sperm can survive up to 5 days in the body – Sex (copulation) must occur no more than 5 days before or 1 day after ovulation Pregnancy • If pregnancy is established, menstruation does not occur. • Fertilized egg is called a zygote. – Once cell division brings the total cell count to around 8, it is called a blastocyst. • Takes 3-5 days for blastocyst to travel through oviduct to uterus. • Blastocyst must implant into endometrium – Occurs 2-4 days after reaching the uterus Fertilization • If pregnancy is established, menstruation does not occur. • Fertilized egg is called a zygote. – Once cell division brings the total cell count to around 8, it is called a blastocyst. • Takes 3-5 days for blastocyst to travel through oviduct to uterus. • Blastocyst must implant into endometrium – Occurs 2-4 days after reaching the uterus Fertilization • If pregnancy is established, menstruation does not occur. • Fertilized egg is called a zygote. – Once cell division brings the total cell count to around 8, it is called a blastocyst. • Takes 3-5 days for blastocyst to travel through oviduct to uterus. • Blastocyst must implant into endometrium – Occurs 2-4 days after reaching the uterus Fertilization • If pregnancy is established, menstruation does not occur. • Fertilized egg is called a zygote. – Once cell division brings the total cell count to around 8, it is called a blastocyst. • Takes 3-5 days for blastocyst to travel through oviduct to uterus. • Blastocyst must implant into endometrium – Occurs 2-4 days after reaching the uterus Pregnancy • During implantation, the blastocyst produces a hormone called HCG – Human chorionic gonadotropin – Prevents degeneration of corpus luteum – Stimulates corpus luteum to increase progesterone secretion • Maintains uterine lining • Prevents contractions – Pregnancy test detects HCG in the urine of women. • “Turns the stick blue” Pregnancy • Tissue grows out from the embryo and mingles with endometrium to form placenta – A disc-shaped organ – Size of dinner plate – Weighs less than 1 kg. – Contains maternal & fetal blood vessels • NO mixing of maternal and fetal blood!! – Diffusion of gasses, nutrients, & wastes – Continues production of HCG, estrogen, progesterone • Maintains endometrium • Corpus luteum not needed – dissolves Pregnancy • Progesterone & estrogen have a negative feedback effect on the hypothalamus – No secretion of FSH – No secretion of LH – No new follicles mature • Embryo remains firmly attached to placenta by umbilical cord. Pregnancy • Umbilical cord –Contains: • 2 fetal arteries –Fetus to placenta • One fetal vein –Placenta to fetus Pregnancy Childbirth • • Also called parturition 38 – 42 weeks from conception – Average = 40 weeks • Three stages of childbirth 1. Labour 2. Delivery 3. Afterbirth Childbirth 1. Labour – Involuntary – Rhythmic contractions of the uterus – Causes cervix to open • Diameter = 10 cm 2. Delivery – Involuntary uterine contractions – Conscious abdominal contractions – Mother forces baby out through cervix and vagina Childbirth 3. Afterbirth – Immediately after delivery – Blood vessels in placenta contract – Placenta separates from uterine wall – Expelled by muscle contractions Childbirth • Why?? – Nobody totally knows. – Baby plays some role in the timing. – Progesterone decreases • Allows uterus to contract – Oxytocin from posterior pituitary • Stimulates stronger uterine contractions – Relaxin • produced by placenta • Causes ligaments of pelvis to loosen • Larger passageway for baby Lactation • During pregnancy, high levels of estrogen and progesterone prepare the breasts for milk production – Each breast has about 20 milk glands – Connect to the nipple by ducts – Breast enlarges during pregnancy in preparation for lactation • Expulsion of the placenta causes the mother's pituitary to secrete prolactin, – Initiates lactation Lactation • Prolactin inhibits the release of LH – menstrual cycle is suppressed in nursing mothers • The high estrogen and progesterone levels during pregnancy are thought to inhibit release of prolactin Lactation • The first fluid formed by the mammary glands is colostrum, – Thick – contains lactose and milk proteins, – lacks fat – after a few days, milk is produced • Oxytocin is released from hypothalamus when infant suckles – Causes milk to be released from mammary glands Fetal Development • A blastocyst – embeds in the uterine wall – Consists of cells of the future embryo – Surrounded by a sphere of cells • Embryonic membrane (extraembryonic membrane) • Support the developing embryo Fetal Development • Amnion – Innermost embryonic membrane • Next to baby • Fluid-filled sac that cushions the baby Fetal Development • Chorion –Outermost membrane • Part of the placenta • Secretes HCG 113 Fetal Development • Umbilical cord – Connection between mother and baby • Belly-button to placenta – Carries baby’s blood to and from placenta Embryonic Development • Placenta (review) – A disc-shaped organ – Size of dinner plate – Contains maternal & fetal blood vessels • NO mixing of maternal and fetal blood!! – Diffusion of gasses, nutrients, & wastes – Continues production of HCG, estrogen, progesterone Embryonic Development • A blastocyst undergoes gastrulation – Series of cell movements and shape changes – Produces an embryo with 3 cellular layers 1. Ectoderm • Outer layer of cells • Will become skin and nervous system 2. Mesoderm • Middle layer of cells • Skeleton, muscles gonads, kidneys, circulatory system 3. Endoderm • Inner layer of cells • Liver, pancreas, lungs, lining of digestive tract Gastrulation Human Gestation • 1st Trimester –From fertilization to end of 3rd month (0 – 13 weeks) –Zygote begins cell division as it moves down oviduct –Becomes blastocyst and implants in uterus Human Gestation • 1st Trimester – Development of body organs – Heart starts beating by week 4 – Week 7, testosterone begins to be secreted if a Y-chromosome is present • This testosterone causes development of testes. Human Gestation • 1st Trimester – By week-8 all major structures of the adult are present (in basic form) • Embryo is now called a fetus – Embryo is most sensitive during first trimester • Due to rapid development • Sensitive to radiation and drugs Gastrulation Gastrulation 6 weeks 7 weeks Gastrulation Gastrulation 8 Weeks 8 weeks 10 Weeks 11 Weeks 11 Weeks 14 Weeks Human Gestation • 2nd Trimester – Fetus grows rapidly • To about 30 cm – Quite active – Hair begins to develop – Cartilage of skeleton is replaced by bone 18 weeks Gastrulation The Hand Picture May 2, 2000 USA Today 133 An Amazing Story -- Aug.19, 1999 • Samuel Armas' tiny hand grips Dr. Joseph P. Bruner's finger just as Bruner finishes returning him to his mother's womb. • Bruner, director of fetal diagnosis and treatment at Vanderbilt University Medical Center (Nashville), was performing a cutting-edge procedure on the 21-week-old fetus. • The procedure on Samuel took about an hour. 134 An Amazing Story -- Aug.19, 1999 • Bruner and Samuel's parents hope the surgery will alleviate the effects of spina bifida, a disabling birth defect in one or two of every 1,000 babies born. • Because fetuses undergoing this procedure are so young -- Samuel could not survive outside his mother's womb -this kind of surgery is gaining attention nationwide from the medical community and the media. 135 An Amazing Story -- Aug.19, 1999 • During the procedure, surgeons remove the uterus from the mother, drain the amniotic fluid, perform surgery on the tiny fetus, replace everything and put the entire package back inside the mother. • Dr. Bruner said regarding the picture, "The baby did not reach out," Bruner says. "The baby was anesthetized. The baby was not aware of what was going on." 136 An Amazing Story -- Aug.19, 1999 • Bruner says he saw the hand "sort of pop up in the incision" on the womb, and he "reached over and picked it up." • Samuel, now nearly 5 months old [may 2, 2000], & is “developing normally and hitting his monthly milestones. He smiles often and is nearly sitting up on his own.” • It will take years to know how much difference the surgery made, but Alex Armas [father] says he's happy the photo has been seen by millions. 137 Samuel Armas 21 weeks Human Gestation • 3rd Trimester – Rapid growth of fetus • To about 53 cm • 3-3.5 kg – Fetal activity decreases • Less room to move – Fully mature – Ready for birth Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Parturition Reproductive Technologies Birth Control • Sterilization – Most effective – In males vas deferens is cut off and sealed • Only effects sperm content of semen so minimal side effects – In females tubal ligation or cutting of the oviducts • Disadvantages of sterilization - hard to reverse Birth Control • “The pill" – A combination of estrogen and progesterone given for 21 days of the 28 day cycle – Effectively shuts down FSH and LH production so follicles do not develop. – Many of the early problems have been sorted out but side effects possible Birth Control • Barrier Methods – Diaphragms, Cervical Caps, Vaginal Sponges, Condoms • Condom – fits over the penis and prevents semen from entering the female; • Diaphragm – which fits over the cervix and prevents semen from entering the uterus • both of these methods are more reliable when used in conjunction with a spermicidal foam or jelly Birth Control • IUD – Inter-Utarian Device – placed in the uterus by a physician, – prevent implantation of the blastocyst in the endometrium. – Best for women who have had one pregnancy, middle to older and are at low risk for STI’s Birth Control • "Natural family planning" – Requires knowledge of the day of ovulation – If known, can avoid the 4 days either side of ovulation to account for unusually long -lived sperm or eggs. – Women need exceptionally regular cycles to be effective – "Basal" body temperature measurements (T rises at ovulation), vaginal pH measurements (more alkaline), mucus thickness can help determine time ovulation. Birth Control • "Morning after pill“ – Most are essentially a controlled overdose of normal birth control pills – RU-486 now distributed by Planned Parenthood. – Blocks progesterone receptors causing uterine lining to slough off taking embryo with it. – Many people have ethical problems with these pills since they remove fertilized eggs. • i.e. after "conception" has occurred. • “abortion pill” Reproductive Technologies • Ultrasound – the use of high-frequency sound waves to visualize the fetus • Amniocentesis – a long needle is used to remove a sample of amniotic fluid from the amniotic sac surrounding the fetus, – fetal cells in the fluid are cultured for 2 to 4 weeks and then analyzed for chromosomal defects and other genetic disorders Amniocentesis Reproductive Technologies • Chorionic Villi Sampling (CVS) – a small sample of tissue is removed from the chorion, • the fetal part of the placenta. – Can be performed earlier in the pregnancy than amniocentesis – results can be obtained within a few days – greater risk of spontaneous abortion from CVS than from amniocentesis – ethical considerations: essentially all detectable fetal disorders remain untreatable in the uterus, and many cannot be corrected even after birth Reproductive Technologies • In Vitro Fertilization – ova can be surgically removed from a woman whose oviducts are blocked – These are fertilized in a petri dish in a laboratory – The resulting embryos can than be inserted into the woman's uterus (or into a surrogate mother's uterus) – Ethical considerations: post-menopausal woman can now have children; in surrogacy, who is the legal mother??? STIs Crabs Epididimitis Genital Warts Syphilis Gonorrhea STIs • Syphilis – caused by a spirochete bacterium. – The first symptoms of syphilis may go undetected because they are very mild and disappear spontaneously. – The initial symptom is a chancre; • usually a painless open sore that usually appears on the penis or near the mouth, anus, or on the hands. STIs – may go on to more advanced stages, including a transient rash and, eventually, serious involvement of the heart and central nervous system. – The full course of the disease can take years. – Penicillin remains the most effective drug to treat people with syphilis. Initial Chancre on Hand STIs • Gonorrhea – discharge from the vagina or penis • “Ooooze” – and painful or difficult urination. – The most common and serious complications occur in women and, these complications include PID, ectopic pregnancy, and infertility. – Historically, penicillin has been used to treat gonorrhea, but in the last decade, four types of antibiotic resistance have emerged. – New antibiotics or combinations of drugs must be used to treat these penicillin resistant strains. STIs • Chlamydia – many cases involve no symptoms and therefore infected persons may not seek medical treatment. – This infection is now the most common of all bacterial STD's, with an estimated 4 to 8 million new cases occurring each year. – In both men and women – abnormal genital discharge – burning with urination – In women, untreated chlamydial infection may lead to pelvic inflammatory disease, • one of the most common causes of ectopic pregnancy and infertility in women. STIs – Many people with chlamydial infection, however, have few or no symptoms of infection. – Once diagnosed with chlamydial infection, a person can be treated with antibiotics STIs • Genital herpes – Affects an estimated 60 million Americans. – Approximately 500,000 new cases of this incurable viral infection develop annually. – Caused by herpes simplex virus (HSV). – painful blisters or open sores in the genital area. – These may be preceded by a tingling or burning sensation in the legs, buttocks, or genital region. – The herpes sores usually disappear within two to three weeks, but the virus remains in the body for life and the lesions may recur from time to time. STIs • Genital herpes – Severe or frequently recurrent genital herpes is treated with one of several antiviral drugs that are available by prescription. • These drugs help control the symptoms but do not eliminate the herpes virus from the body. • Suppressive antiviral therapy can be used to prevent occurrences and perhaps transmission. – Women who acquire genital herpes during pregnancy can transmit the virus to their babies. – Untreated HSV infection in newborns can result in mental retardation and death. STIs • AIDS (acquired immunodeficiency syndrome) • First reported in the United States in1981. • It is caused by the human immunodeficiency virus (HIV), – a virus that destroys the body's ability to fight off infection. • An estimated 900,000 people in the United States are currently infected with HIV. • People who have AIDS are very susceptible to many life-threatening diseases (called opportunistic infections) and to certain forms of cancer. • Transmission of the virus primarily occurs during sexual activity and by sharing needles used to inject intravenous drugs. STIs • Genital warts – Caused by human papillomavirus, • a virus related to the virus that causes common skin warts. – Genital warts usually first appear as small, hard painless bumps in the vaginal area, on the penis, or around the anus. – If untreated, they may grow and develop a fleshy, cauliflower-like appearance. – Genital warts infect an estimated 1 million Americans each year. – In addition to genital warts, certain high-risk types of HPV cause cervical cancer and other genital cancers. – Genital warts are treated with a topical drug (applied to the skin), by freezing, or if they recur, with injections of a type of interferon. – If the warts are very large, they can be removed by surgery. STIs • Genital herpes – Affects an estimated 60 million Americans. – Approximately 500,000 new cases of this incurable viral infection develop annually. – Caused by herpes simplex virus (HSV). – painful blisters or open sores in the genital area. – These may be preceded by a tingling or burning sensation in the legs, buttocks, or genital region. – The herpes sores usually disappear within two to three weeks, but the virus remains in the body for life and the lesions may recur from time to time. STIs • Genital herpes – Affects an estimated 60 million Americans. – Approximately 500,000 new cases of this incurable viral infection develop annually. – Caused by herpes simplex virus (HSV). – painful blisters or open sores in the genital area. – These may be preceded by a tingling or burning sensation in the legs, buttocks, or genital region. – The herpes sores usually disappear within two to three weeks, but the virus remains in the body for life and the lesions may recur from time to time.