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BPK 140 (134)
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Chapter 10

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Department
Biomedical Physio & Kines
Course
BPK 140
Professor
Michael Walsh
Semester
Fall

Description
1 KIN 140 Section 11 Dr Mike Walsh SEX I. Sexuality One’s sexuality is a product of their biology and the social conditioning they have received. Biology is used to determine if someone is male or female. Man and woman refer to the psychosocial roots of our sexuality.And masculinity and femininity refers to the resultant of one’s biology and psychosocial experience. A. Biological Basis of Sexuality 1. Genetic Basis The biological basis of our sexuality is determined by whether an X sperm cell or a Y sperm cell wins the race to the egg. The egg is haploid (one set of chromosomes) X if it is fertilized by a haploid X sperm cell, a biological female (diploid) is produced. If the haploid X egg is fertilized by a haploid Y sperm cell then a biological male is produced. 2. Gonadal Basis Development of gonads: testes for males and ovaries for females, occurs within the first trimester of pregnancy. Development of male reproductive organs will take place if there is a presence of the SRY gene (sex-determining region on the Y chromosome) is expressed to make the protein testis-determining factor (TDF). If the SRY gene is not present, then female gonads will develop. 3. Structural Basis In general, there is slow growth through childhood. In puberty there is an increase in male and female hormone (testosterone and estrogen (both are also needed for gonadal basis) that stimulates the growth of secondary sexual characteristics. In females, menarche also occurs at this time and both genders become capable of sexual reproduction. In males, normally testosterone is converted to a more potent form, dihydrotestosterone, by the enzyme 5-alpha reductase. Males lacking this enzyme often have female appearance and genitals and behaviour until puberty then develop male sex organs and behavior. 2 In the Dominican Republic, the incidence of 5-alpha reductase deficiency can be 1-2 %. These male children are called 'guevedoces' (literally, penis at 12 years). In later life, they to do not have male pattern baldness 4. Aging Females are born with a full complement of eggs.At menopause they have an abrupt cessation of reproductive capacity. This usually occurs at the age of about 50. Males have a gradual reduction in spermatogenesis but can be still be reproductive past 70. While there is some debate about exact egg number, it is remarkable that one cell can last 50 yr. B. Psychosocial Basis of Sexuality 1. Gender Identity By the age of about 18 months, the infant recognizes itself as male or female and is quite robust by 3 yr. It is your own personal feelings combined with what you think you have in common with others. 2. Gender Preference The infant and child are steered subtly and /or overtly toward behaviours considered appropriate for the gender. This is done primarily by the parents but also by many outside influences. Whether this gender preference stage is truly environmental or has some genetic basis is open for discussion. Either way, if you ask some 7 year old children if they would be happier changing gender, you will get some very definitive responses. Certainly most children are very comfortable with their bodies, except for perhaps obesity. 3. Gender Adoption Observing, watching, and practicing what adults do enables the child and adolescent to begin thinking, feeling, and acting like an adult of their gender. Obviously, television can play a large part in gender adoption. Also learning the psychological attributes of the opposite gender is important to the development of a balanced sexuality. 3 4. Adult Gender Identification The final development of an adult image of oneself is in a gender-specific context. Of course this image may differ substantially between people because of their differing genetics and experience. This final image may also be changing with time: male levels of testosterone and viable sperm are decreasing. 5. Androgyny (andro=male, gyny=female) Androgyny is having a self-image that incorporates aspects of both genders. This combination of masculine and feminine qualities is more prevalent today than in past decades and centuries. In general, people who demonstrate a less polarized sexual image and a more androgynous one have greater self-esteem, more social, psychologically more flexible, and have more motivation to achieve. C. Sex Anatomy and Physiology 1. Female Sex Organs The female anatomy in their genital region, from anterior to posterior, is the clitoris, urinary opening, vaginal opening, and anus. The clitoris is very sensitive to touch, hence it plays an important part of sexual arousal and orgasm. The vaginal opening leads to the internal reproductive organs. It is the orifice of choice for most heterosexual intercourse, and it is also the birth canal. The vaginal opening is initially partially covered by the hymen. The hymen is ruptured during a woman’s first intercourse. It can also be ruptured by athletic activity. This means the absence of a hymen is not necessarily an indication of lost virginity. 2. Male Sex Organs Male organs in the genital area going anterior to posterior are the penis, testicles, and anus. At the head of the penis is the opening for the urethra, which serves for both the voiding of urine and ejaculation of semen. 4 The testicles are, by design, located exterior to the body core to maintain sperm temperature about 2.5 C lower than core temperature. Small changes in temperature strongly affect the viability of the sperm. The scrotum can substantially decrease its size when temperature is lower. 3. Circumcision This is when a male cuts off another male’s (not anesthetized) foreskin when all the other males leave the room. The reasons for this are cultural and religious. There is very little medical evidence to support the prevalence of this procedure. However, lately it has been shown that circumcised males suffer less STDs. This can be important in Africa since circumcision may reduce the spread ofAIDS. 4. Female Sexual Cycle (aka Menstrual Cycle) The menstrual cycle is a monthly ovarian (thus female) cycle in which an egg is made receptive to fertilization and if fertilization does not occur there is a loss of blood and the enriched tissue lining of the uterus. The average female cycle is about 28 days although the duration between women does vary from 20-45 days. The average female’s first menstrual cycle (aka menarche) occurs at 12.8 yr with a substantially large but normal range. The menstrual cycle consists of 4 phases: menses, estrogenic phase, ovulation, and progestational phase. a. Menses The onset of menstrual bleeding indicates day 1. With low levels of estrogen and progesterone, the outer portions of the endometrial lining degenerate and separate from the endometrium. The loss of blood and epithelial lining normally lasts about 5 days. b. Estrogenic Phase (aka Follicular Phase: ~8 days) Begins when menstrual flow ceases. Luteinizing hormone (LH) and follicle stimulating hormone (FSH) are released in greater amounts from the anterior pituitary gland. Follicle stimulating hormone stimulates the egg/follicle to make estrogen. The uterine lining (endometrium) begins to thicken and gets enriched with blood vessels and glands in response to the increasing estrogen produced by the follicle. Thus the endometrium is prepared for implantation by a fertilized egg. 5 During this phase 5-25 follicles are released. Of these, a single follicle increases in size from 25 um to 15 mm diameter in response to the combined effects of LH, FSH, and estrogen. Of course the egg inside the follicle is much smaller. c. Ovulation (1 day) Rapid increase in estrogen stimulates an increase in LH which induces ovulation: the release of the ovum from the follicle. This occurs at about day 14. The remaining follicle becomes the corpus luteum. d. Progestational Phase (aka Luteal Phase: 7-13 days) The remaining follicle tissue becomes luteinized (made yellowish) into the corpus luteum (yellow body). The corpus luteum is a separate endocrine organ that generates progesterone secretion and estrogen secretion. These hormones (especially progesterone at this time) stimulate the continued growth and development of the endometrial lining. They also inhibit further secretion of LH and FSH from the pituitary gland. If the egg does not become fertilized in the next about 12 days, the corpus luteum is preprogrammed to degenerate. Estrogen and progesterone decrease and can no longer maintain the uterine lining which then becomes the start of menses. Women are more creative in this phase. D. Responsible Sexual Behaviour 1. Communication It is difficult to express your intentions and determine your partner’s when the hormones are flowing. To practice responsible sexual behaviour, it is necessary to understand why the sexual activity is occurring. Sex can be to express love, make babies, or attain physical gratification. Most sexual acts involve the latter. Most high school-aged males that engage in sexual activ
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