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Chapter 27 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. 27-1 Sexuality from Different Points of View Sexuality – – – – Different approaches to sexuality – – – 27-2 All of the factors that contribute to one’s female or male nature Structure and function of sex organs Sexual behavior Cultural influences Behavioral Cultural Biological Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A Spectrum of Human Sexuality 27-3 Ranges from heterosexual to homosexual A complex trait; no one gene dictates where one falls on spectrum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sexual Attraction, Sex and Sexual Response Sexual attraction involves many factors, including sight and smell. After initial attraction, the couple may engage in foreplay and sexual intercourse. – – – 27-4 In heterosexual sex, the male achieves an erection of the penis, which allows it to be easily inserted into the female vagina. Pelvic movements can result in ejaculation, which allows for release of sperm and other fluids (semen) from the penis, and is accompanied by a pleasurable sensation called orgasm. Females often also experience orgasm. Maintaining an active sex-life in a long-term relationship requires effort. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Moving Across the Spectrum Pseudo-hermaphrodites – – – 27-5 Humans born with partial development of both male and female genitalia Due to a hormonal imbalance during embryonic development Gender must be “chosen” and genitalia surgically altered to become completely female or completely male Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Moving Across the Spectrum Gender dysphoria – – – – 27-6 When one’s physical and psychological gender do not match A male who “feels” like a woman, or vice versa Frequently these individuals dress and act as members of the opposite sex (cross-dressers or transvestites). Often leads to gender-reassignment surgery (sexchange) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nature or Nurture? Studies show that – – A small region of the hypothalamus is of similar size in trans-gendered males as it is in women, and in transgendered females as it is in men. Similar studies show differences in brain structure between homosexuals and heterosexuals. – – 27-7 Not confirmed Complicated because homosexual brain donors were HIV+ and had been on antiviral drugs Genes on chromosomes 7, 8 and 10 have been suggested to influence homosexuality. Homosexuality is a complex behavioral pattern. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromosomal Determination of Sex and Early Development 2 of the 46 human chromosomes are involved in gender determination – Called sex chromosomes X and Y – – Are not truly homologous because they contain different sets of information X carries more information than just that needed for gender determination. – Y carries only information regarding maleness. 27-8 Blood-clotting, color vision, etc. Contains SRY (Sex-determining Y) gene SRY encodes for testes determining factor (TDF) The presence of this gene leads to the development of a male; the absence leads to the development of a female. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromosomal Determination of Sex Eggs carry 22 autosomes and an X. Sperm carry 22 autosomes and either a Y or an X. – – Embryos become truly male or female during differentiation. – – 27-9 If an X sperm fertilizes an egg, a female is formed (XX). If a Y sperm fertilizes an egg, a male is formed (XY). When embryonic gonads develop into ovaries or testes The presence of SRY will lead to the development of testes. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Male and Female Chromosomes 27-10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromosomal Abnormalities and Sex Turner’s syndrome (XO) – Results from a nondisjunction in one parent – Symptoms 27-11 Make egg or sperm that lack a sex chromosome. When this gamete is used during fertilization, the individual ends up with only one sex chromosome, in this case, an X. Abnormally short Failure to complete sexual maturity Thickened neck Hearing impairment Cardiovascular problems Sterility Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Turner’s Syndrome 27-12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromosomal Gender Disorders Klinefelter’s syndrome (XXY) – Also results from a nondisjunction in one parent – Symptoms 27-13 Leads to the development of gametes with two sex chromosomes After fertilization, the individual has three sex chromosomes. Sterility Breast enlargement Incomplete masculine development Lack of facial hair Minor learning problems Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Klinefelter’s Syndrome 27-14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fetal Development and Sex Development of gonads begins about week 5. Males – – – – Between weeks 5-7 testes determining factor made from the SRY gene begins the differentiation of male gonads. Week 8, testes begin making testosterone. Testosterone leads to the differentiation of male sexual anatomy (penis, etc.). In the 7th month, testes move through the inguinal canal to the external sac. If this canal opens again later in life, an inguinal hernia can result. Cryptorchidism – – 27-15 Failure of testes to descend Can lead to sterility unless corrected Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fetal Development and Sex 27-16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fetal Development and Sex Females – – 27-17 Ovaries develop about week 12 in the absence of TDF. The absence of testosterone leads to the differentiation of female sexual anatomy (vagina, etc.). Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sexual Maturation in Young Adults Puberty is the developmental period when: – – 27-18 The body changes to the adult form. The body becomes sexually mature and able to produce offspring. Usually occurs between 12-14 years old Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormones and Sexual Function 27-19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Females At 9-12 years of age – Hypothalamus and pituitary gland – – – – 27-20 The hypothalamus, pituitary, ovaries and adrenal glands begin producing sex hormones. Hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the pituitary to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). FSH stimulates the development of follicles in the ovary. LH stimulates the ovary to produce more estrogen. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Females Estrogen stimulates secondary sex characteristics. – – – Growth of breast tissue Maturation of the uterus and vagina Increased blood supply to the clitoris – – Changes in pelvic bone structure Production of androgens by adrenal gland 27-21 The clitoris is a small, elongated erectile structure located at the head of the labia. It is equivalent to the penis. Leads to the growth of pubic hair Influence female sex drive Involved in the production of acne Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Females During puberty, females begin to experience the menstrual cycle. – – LH from the pituitary causes the egg to be released from the follicle in the ovary (ovulation). The ruptured follicle becomes the corpus luteum. – 27-22 Begins releasing progesterone Progesterone maintains the lining of the uterus. When uterine lining breaks down, menstruation occurs. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ovulation 27-23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Males Between 11-14 years of age in males, the hypothalamus releases GnRH. Like in females, GnRH stimulates the pituitary to release LH and FSH. – – – 27-24 LH is also called interstial cell-stimulating hormone (ICSH) in males. LH stimulates the production of testosterone by the testes. FSH stimulates the production of sperm cells. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Males Testosterone stimulates the development of male secondary sex characteristics. – – – – – – – 27-25 Increased size of the penis Growth of testes and scrotum Growth of pubic hair Facial and body hair Larynx changes shape, leading to the deepening of the male voice Increased height Body shape changes (broad shoulders, more muscles) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Maturation of Males Semen production – – – Mixture of sperm and secretions released during ejaculation Involves seminal vesicles, prostate gland, and bulbourethral gland Seminal vesicles secrete an alkaline fluid that contains fructose and hormones. – – 27-26 Alkaline fluid neutralizes the acidic nature of the female reproductive tract. Fructose is fuel for the sperm. Prostate gland produces a thin milky fluid containing sperm-activating hormones. Bulbo-urethral gland produces alkaline secretions. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gametogenesis The process of producing gametes – – 27-27 Spermatogenesis is the process of producing sperm, the male gamete. Involves meiosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spermatogenesis Takes place in the seminiferous tubules of the testes The seminiforous tubules converge and become the epididymis. – The epididymis leads into the vas deferens (sperm duct). The vas deferens empties into the urethra. – 27-28 Sperm are stored here and mature prior to ejaculation. Conducts sperm out of the body through the penis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sperm Production 27-29 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Human Male Reproductive System 27-30 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spermatogenesis After puberty the cells in the seminiferous tubules begin to undergo meiosis. – – – 27-31 Meiosis I produces two haploid cells. Meiosis II produces four spermatids. Spermatids lose most of their cytoplasm and develop long tails and mature into sperm. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spermatogenesis Sperm – – – – – – 27-32 Have only a small amount of food Very active when released Live about 72 hours Can be deactivated and frozen for use in artificial insemination Are produced throughout the life of a male Normal males produce about 150 million sperm/ml. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis Oogenesis is the production of egg cells in females. – – Occurs via meiosis in the ovary Begins during prenatal development of the ovary 27-33 Special cells in the ovary stop dividing by mitosis and enlarge. These are future eggs, called primary oocytes. They go through the early stages of meiosis and stop until after puberty. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis At puberty (and every month after) – FSH stimulates a primary oocyte to complete meiosis. 27-34 Meiosis I generates two cells, but one receives most of the cytoplasm. The smaller cell is called a polar body. The larger cell will become the egg. Prior to ovulation, the larger cell becomes encased in a follicle. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis 27-35 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis When the follicle is mature, LH stimulates it to release the egg into the fallopian tube (oviduct). – – Once ruptured, the follicle becomes the corpus luteum. The corpus luteum releases progesterone that prevents the release of more eggs. 27-36 The egg travels through the fallopian tube to the uterus. The egg completes meiosis in the uterus after it is fertilized. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis If it is not fertilized, it is released from the body through the vagina during menstruation. Since eggs begin production during embryonic development, the older a woman is, the older her eggs are. – 27-37 Contributes to abnormal births that are more common in older women. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Human Female Reproductive System 27-38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormonal Control of Female Sexual Cycles Estrogen and progesterone stimulate changes in the female body that will support a pregnancy. – – If fertilization does not occur, menstruation results. – – – 27-39 Growth of uterine lining Milk production in breasts Lining of uterus breaks down and is released (menses) Once shed, the lining begins to build back up again. This cycle happens about once a month. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Menstruation is Coordinated with Ovulation FSH causes the follicle to grow. At the same time, the follicle releases estrogen. – After ovulation, LH stimulates the ruptured follicle to become a corpus luteum. The corpus luteum releases progesterone. – 27-40 This increases blood flow to the uterine lining. If the egg is not fertilized, the corpus luteum will break down. – This causes the uterine lining to become thicker. This reduces the amount of progesterone released. Without progesterone, the uterine lining breaks down and is shed. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Ovarian and Uterine Cycles in Human Females 27-41 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormonal Control of Fertility Fertility drugs – Hormones given to women to stimulate the release of eggs from the ovary (ovulation) – Will often result in the release and fertilization of more than one egg 27-42 May increase the likelihood of achieving pregnancy May be retrieved for use in in vitro fertilization Leads to multiple implantations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormonal Control of Fertility Female contraception – – Male contraception – – 27-43 Estrogen and progesterone inhibits ovulation. Can help relieve the symptoms of PMS Testosterone and progesterone can temporarily turn off the production of sperm. Newly developed Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Common Causes of Infertility 27-44 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fertilization, Pregnancy and Birth In most women, the egg is released on day 14 of the menstrual cycle. – Once released, the egg is moved into the oviduct toward the uterus. The egg must be fertilized in the oviduct. – – 27-45 About 2 weeks before the next menstruation Sperm swarm around the egg, but only one penetrates it. The other sperm contribute an enzyme that digests away the mucus barrier around the egg. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fertilization Once fertilized, the egg can complete meiosis. – – The second polar body is pinched off. The true ovum is formed. The chromosomes from the ovum and the sperm pair up, forming a diploid zygote. The zygote begins to divide by mitosis. – This process is called cleavage. 27-46 Produces a ball of cells called a morula The morula continues to divide to form a blastocyst. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pregnancy The blastocyst travels down the oviduct and enters the uterus. – The blastocyst continues to divide and the cells migrate and differentiate to form an embryo. The embryo is contained within the amnion. – In the uterus, the blastocyst implants into the uterine lining. A fluid-filled sac that keeps the embryo moist The chorion and allantois fuse with the lining of the uterus to form the placenta. – – Provides nutrients to the embryo Stimulates the corpus luteum to continue releasing progesterone 27-47 Inhibits ovulation and menstruation during pregnancy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Placental Structure 27-48 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Embryonic Development As the embryonic cells divide, they become differentiated into specialized cell types. Molecules from the mother provide nourishment for this process. – Harmful substances that the mother may ingest can disrupt the development of the embryo. 27-49 Alcohol, drugs, medication, viruses, etc. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Embryonic Development 27-50 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Twins Twinning occurs in two ways. – Identical twins are the result of the splitting of the embryo during cleavage. – Fraternal twins are the result of a double fertilization event. 27-51 These individuals are genetically identical. Two separate eggs are fertilized by two separate sperm at the same time. Are no more genetically similar than any other set of siblings. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Twins 27-52 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Birth Also known as parturition or birthing At the end of about 9 months of pregnancy, hormonal changes stimulate uterine contractions. – – Involves oxytocin from the posterior pituitary The contractions Cause the amnion to burst (water breaking) Move the baby head first, face down through the vagina (birth canal) – 27-53 If the baby is oriented feet first (breech), oxygen supply from the placenta could be cut off. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Childbirth 27-54 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Birth Breech and other fetal position problems can be resolved by performing a C-section birth. – An incision in the abdomen is made and baby is removed. After the baby is born – The placenta is expelled. – 27-55 – Also called afterbirth The umbilical cord collapses and the baby begins to breathe and function on its own. The mother’s breasts begin to produce milk. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Contraception 27-56 Also called conception control There are many methods to prevent ovulation and/or fertilization. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Methods Contraceptive (spermicidal) jellies and foam – – – – 27-57 Placed into the vagina prior to intercourse Increase the acidity of the vagina Lowers the sperms’ chances of survival Do not protect against sexually-transmitted diseases Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormonal Control Methods The birth control pill, implant or patch – – – 27-58 Prevents ovulation by manipulating estrogen and progesterone levels The hormones “fool” the ovary into thinking that the woman is already pregnant. Hormones can be delivered in a pill, implant, patch or vaginal ring. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hormonal Control Methods The “morning after” pill – – High dose of the hormones in birth control pills Can prevent 27-59 Ovulation Transport of egg and sperm Fertilization Implantation of fertilized egg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Timing Method Also called the rhythm method Prevents sperm from coming into contact with an egg Involves avoiding intercourse during the time of the menstrual cycle when ovulation is likely happening – – 27-60 Usually a few days before and after day 14 Can be estimated by tracking changes in body temperature and vaginal pH Not effective for women with irregular menstrual cycles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Barrier Methods Involves preventing the sperm from reaching the egg Diaphragm – – Contraceptive sponge – – 27-61 Specially fitted, membranous shield that is inserted into the vagina before intercourse Covers the cervix and serves as a barrier to sperm entering the uterus A sponge soaked in a spermicide that is placed within the vagina No longer available in the USA Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Barrier Methods Condom – – Thin sheath of rubber placed over the penis before intercourse Provides a physical barrier to sperm – Protects against sexually-transmitted diseases Female condom – 27-62 Some are coated with spermicide as well. A polyurethane sheath that lines the vagina Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Barrier Methods 27-63 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. IUD An apparatus that is inserted and fitted in the uterus – 27-64 Must be performed by a physician Thought to interfere with implantation Can be used after unprotected sex to prevent pregnancy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Surgical Methods Tubal ligation – – Vasectomy – – – 27-65 Involves cutting and tying off the oviducts (Fallopian tubes) Ovulation occurs, but sperm and egg cannot meet. The vas deferens (sperm duct) is cut and tied. Prevents sperm from entering semen Does not interfere with sex drive or ejaculation. Both procedures are generally irreversible. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tubal Ligation and Vasectomy 27-66 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Termination of Pregnancy— Abortion A medical procedure that causes the death and removal of the developing embryo or fetus A highly controversial subject Can be done in a number of ways – Dilation and curettage (D and C) involves – The drug RU-486 27-67 Scraping the inside of the uterus Injecting a saline solution into the uterus Using a suction device to remove the embryo Induces uterine contractions that expel the embryo Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Changes in Sexual Function with Age Menopause in women – – About age 50, hormone production changes in the ovaries This change in hormone balance causes ovulation to stop along with other symptoms. – – 27-68 Mood swings Cramps Hot flashes The symptoms can be treated with hormone replacement therapy. Sexual enjoyment is not significantly affected. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Changes in Sexual Function with Age Males – – Production of sperm declines May experience impotence Lack of sexual desire Erectile dysfunction – Recurrent inability to get an erection firm enough for intercourse – Can be caused by injury, disease, or medication – Can be treated with medications such as Viagra or Levitra – Sexual desire decreases with age 27-69 Problems with ejaculation May involve changes in hormone levels Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.