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The Reproductive System The Reproductive System • Gonads—primary sex organs ▫ Testes in males ▫ Ovaries in females • Gonads produce gametes (sex cells) and secrete hormones ▫ Sperm—male gametes ▫ Ova (eggs)—female gametes Female Reproductive System • Ovaries • Duct System ▫ Uterine tubes (fallopian tubes) ▫ Uterus ▫ Vagina • External genitalia Female Reproductive System Figure 16.8a Ovaries • Within each ovary are structures called ovarian follicles ▫ Each follicle consists of an immature egg called a oocyte ▫ Each month in adult women, a follicle ejects its oocytes from an ovary Called ovulation Figure 16.7 Figure 16.11 Duct System •Uterine tubes (fallopian tubes) •Uterus •Vagina Uterine (Fallopian) Tubes • Receive the ovulated oocyte and provide a site for fertilization • Attach to the uterus • Little or no contact between ovaries and uterine tubes • Cilia create currents that carry oocytes into the tubes • Carried to the uterus by peristalsis and beating of cilia Female Reproductive System Figure 16.8b Uterus • Hollow thick walled muscular organ • Functions of the uterus ▫ Receives a fertilized egg ▫ Retains the fertilized egg ▫ Nourishes the fertilized egg • Narrow neck of the uterus that projects into the vagina is called the cervix Uterus • The uterine wall is composed of 3 layers ▫ Perimetrium ▫ Myometrium ▫ Endometrium • If fertilization occurs, the embryo burrows down into endometrium and develops there • If no fertilization occurs, the endometrium is shed during menstruation Vagina • Extends from cervix to exterior of body • Serves as the birth canal • Receives the penis during sexual intercourse • Hymen—partially closes the vagina until it is ruptured • The pH of vagina is acidic, which keeps it free from infection and hostile to sperm Clitoris • Contains erectile tissue • Corresponds to the male penis • The clitoris is similar to the penis in that it is ▫ Composed of sensitive erectile tissue ▫ Becomes swollen with blood during sexual excitement Mammary Glands • Present in both sexes, but only function in females ▫ Modified sweat glands • Function is to produce milk • Stimulated by sex hormones (mostly estrogens) to increase in size Female Mammary Glands Figure 16.13a Male Reproductive System Overview • Testes • Duct system ▫ Epididymis ▫ Ductus (vas) deferens ▫ Urethra Male Reproductive System Overview • Accessory organs ▫ Seminal vesicles ▫ Prostate ▫ Bulbourethral glands • External genitalia ▫ Penis ▫ Scrotum Male Reproductive System Figure 16.2a Testes • Each lobule contains one to four seminiferous tubules ▫ Tightly coiled structures ▫ Function as sperm-forming factories Figure 16.5a Testes Figure 16.1 External Genitalia • Scrotum ▫ Divided sac of skin outside the abdomen ▫ Maintains testes at 3°C lower than normal body temperature to protect sperm viability Epididymis • Functions to mature and store sperm cells ▫ Immature and nearly non-motile sperm leave testes and are moved slowly through the epididymis ▫ By day 20, sperm have gained the ability to sperm • Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens Ductus Deferens (Vas Deferens) • Carries sperm from the epididymis to the ejaculatory duct • Moves sperm by peristalsis • Ends in the ejaculatory duct which unites with the urethra Ductus Deferens (Vas Deferens) • Ejaculation—smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze sperm forward • Vasectomy—cutting of the ductus deferens at the level of the testes to prevent transportation of sperm Urethra • Passageway for both urine and semen Seminal Vesicles • Located at the base of the bladder • Produces a thick, yellowish secretion (60% of semen) ▫ Fructose (sugar) ▫ Vitamin C ▫ Prostaglandins ▫ Other substances that nourish and activate sperm Prostate • Encircles the upper part of the urethra • Secretes a milky fluid ▫ Helps to activate sperm Bulbourethral Glands • Pea-sized gland inferior to the prostate • Produces a thick, clear mucus ▫ Cleanses the urethra of acidic urine ▫ Serves as a lubricant during sexual intercourse Penis • Copulatory organ that delivers sperm to female • Contains spongy urethra composed of 3 cylindrical bodies of erectile tissue ▫ Connective tissue and smooth muscle with vascular spaces ▫ Vascular spaces fill with blood during erection Semen • Mixture of sperm and accessory gland secretions • Advantages of accessory gland secretions ▫ Fructose provides energy for sperm cells ▫ Alkalinity of semen helps neutralize the acidic environment of vagina ▫ Semen inhibits bacterial multiplication ▫ Elements of semen enhance sperm motility Imbalances • Testicular Cancer ▫ Affects one of every 50,000 males and most common cancer among young males ages 1535 ▫ Most common sign is a painless solid mass in testis ▫ Risk factors in development: Nondescent of the testes Maternal exposure to toxins before birth Inflammation of the testis Imbalances • Prostate Cancer ▫ Most common cause of cancer death in men after lung cancer ▫ Risk factors in development: Fatty diets Genetic predisposition Imbalances • PID (Pelvic Inflammatory Disease) ▫ Caused by infection that spreads ▫ Can cause scarring of the uterine tubes and ovaries, which causes sterility Imbalances • Cerival Cancer ▫ Affects about 450,000 women each year, killing almost half. ▫ Most common among women between the ages of 30 and 50. ▫ Risk factors in development: Frequent cervical inflammations STD’s including genital warts Multiple pregnancies Imbalances • Breast Cancer ▫ Most common malignancy and 2nd most common cause of cancer death of U.S. women ▫ 13% of women in the general population (132 out of 1000 individuals) will develop it ▫ Risk factors in development: Early menstruation and late menopause No pregnancies or first one late in life and no or short periods of breast feeding Family history of breast cancer Hormone replacement therapy Imbalances • Breast Cancer ▫ BRCA1 and BRCA2 genes show mutations which can trigger breast cancer ▫ Treatments include: Drug therapy Lumpectomy (only cancerous lump is removed) Mastectomy Mammograms Figure 16.14 Imbalances • STDs ▫ The United States has the highest rate of infection among developed countries ▫ Over 12 million people in the U.S., a quarter of them adolescents, gets STDs each year ▫ They are the single most important cause of reproductive disorders Imbalances • Gonorrhea ▫ Caused by a bacterium that invades the mucus membranes of the reproductive and urinary tracts ▫ Occurs most frequently in adolescents and young adults ▫ Most common symptoms in males is painful urination and discharge of pus from the penis ▫ Females can experience vaginal discharge, uterine bleeding, and abdominal pain Imbalances • Gonorrhea ▫ Caused by a bacterium that invades the mucus membranes of the reproductive and urinary tracts ▫ Occurs most frequently in adolescents and young adults ▫ Most common symptoms in males is painful urination and discharge of pus from the penis ▫ Females can experience vaginal discharge, uterine bleeding, and abdominal pain Imbalances • Syphilis ▫ Caused by a bacterium that is usually transmitted sexually but can pass from an infected mother ▫ After about 2 -3 weeks a red painless lesion appears at the site of infection ▫ If untreated, a pink skin rash can occur and fever and joint pain are common ▫ Disease enter latent period and then can only be detected by a blood test Imbalances • Chlamydia ▫ Infects 4-5 million each year and responsible for 20-50% of all cases of PID ▫ Symptoms include painful and frequent urination, painful intercourse, vaginal and penile discharge ▫ 80% of women do not experience symptoms Major cause of sterility Birth Control Methods • Surgical Sterilization ▫ Vasectomy ▫ Tubal ligation • Hormonal Methods ▫ ▫ ▫ ▫ “the pill” Norplant implant Depro Vaginal ring Birth Control Methods • IUDs (interauterine devices) • Coitus interruptus • Induced Abortion ▫ RU 486 • Barrier methods ▫ Condoms ▫ Diaphragm The Ovarian Cycle • The total supply of eggs are present at birth • Ability to release eggs begins at puberty • Reproductive ability ends at menopause Uterine (Menstrual) Cycle • 4 stages ▫ Menstrual Cycle ▫ Preovulatory Cycle ▫ Ovulation ▫ Postovulatory Cycle Uterine (Menstrual) Cycle • Menstrual phase ▫ Days 1–5 ▫ Functional layer of the endometrium is sloughed ▫ Bleeding occurs for 3–5 days Uterine (Menstrual) Cycle • Preovulatory Stage ▫ Days 6–14 ▫ Regeneration of functional layer of the endometrium ▫ Estrogen levels rise ▫ Ovulation occurs in the ovary at the end of this stage Uterine (Menstrual) Cycle • Ovulation ▫ Release of the oocytes into the pelvic cavity ▫ Usually occurs on day 14 Uterine (Menstrual) Cycle • Postovulatory Stage ▫ Days 15-28 ▫ Time between ovulation and onset of next menstrual cycle Ovarian Cycle Figure 16.12c Uterine (Menstrual) Cycle Figure 16.12d Human Development • Fertilization • Embryonic development • Fetal development • Childbirth Fertilization • The oocyte is viable for 12 to 24 hours after ovulation • Sperm are viable for 24 to 48 hours after ejaculation • For fertilization to occur, sexual intercourse must occur no more than 2 days before ovulation and no later than 24 hours after • Sperm cells must make their way to the uterine tube for fertilization to be possible The Zygote • First cell of a new individual • The result of the fusion of DNA from sperm and egg • The zygote begins rapid mitotic cell divisions • The zygote stage is in the uterine tube, moving toward the uterus Cleavage • Rapid series of mitotic divisions that begins with the zygote and ends with the blastocyst • Zygote begins to divide 24 hours after fertilization • Three to 4 days after ovulation, the preembryo reaches the uterus and floats freely for 2–3 days • Late blastocyst stage—embryo implants in endometrium (day 7 after ovulation) Inner cell mass Blastocyst cavity Cleavage Trophoblast (a) Zygote (fertilized egg) (b) Early cleavage 4-cell stage (c) Morula (d) Early blastocyst (b) Fertilization (a) (e) Late blastocyst (implanting) (c) Ovary (d) Uterine tube (e) Secondary oocyte Ovulation Uterus Endometrium Figure 16.15 Developmental Stages • Embryo—developmental stage until ninth week ▫ Morula—16-cell stage ▫ Blastocyst—about 100 cells • Fetus—beginning in ninth week of development Germ Layers • Ectoderm ▫ Nervous system ▫ Epidermis of the skin • Endoderm ▫ Mucosae ▫ Glands • Mesoderm ▫ Everything else Development After Implantation • Chorionic villi (projections of the blastocyst) develop ▫ Cooperate with cells of the uterus to form the placenta • Amnion—fluid-filled sac that surrounds the embryo • Umbilical cord ▫ Attaches the embryo to the placenta Figure 16.17 Functions of the Placenta • Forms a barrier between mother and embryo (blood is not exchanged) • Delivers nutrients and oxygen • Removes waste from embryonic blood • Becomes an endocrine organ (produces hormones) and takes over for the corpus luteum (by end of second month) by producing ▫ Estrogen ▫ Progesterone ▫ Other hormones that maintain pregnancy The Fetus • All organ systems are formed by the end of the eighth week • Activities of the fetus are growth and organ specialization • This is a stage of tremendous growth and change in appearance Photographs of a Developing Fetus Figure 16.18a Figure 16.18b Table 16.1 (2 of 2) Effects of Pregnancy on the Mother • Pregnancy—period from conception until birth • Anatomical changes ▫ Enlargement of the uterus ▫ Accentuated lumbar curvature (lordosis) ▫ Relaxation of the pelvic ligaments and pubic symphysis due to production of relaxin Effects of Pregnancy on the Mother • Physiological changes ▫ Gastrointestinal system Morning sickness is common due to elevated progesterone and estrogens Heartburn is common because of organ crowding by the fetus Constipation is caused by declining motility of the digestive tract Effects of Pregnancy on the Mother • Physiological changes (continued) ▫ Urinary system Kidneys have additional burden and produce more urine The uterus compresses the bladder, causing stress incontinence Effects of Pregnancy on the Mother • Physiological changes (continued) • Respiratory system Nasal mucosa becomes congested and swollen Vital capacity and respiratory rate increase Dyspnea (difficult breathing) occurs during later stages of pregnancy Effects of Pregnancy on the Mother • Physiological changes (continued) ▫ Cardiovascular system Blood volume increases by 25–40% Blood pressure and pulse increase Varicose veins are common Childbirth (Parturition) • Labor—the series of events that expel the infant from the uterus ▫ Rhythmic, expulsive contractions ▫ Operates by the positive feedback mechanism • False labor—Braxton Hicks contractions are weak, irregular uterine contractions