1. Sexual Anatomy and Physiology

2. Sexual Anatomy: The First Few Steps Our culture focuses considerable attention on sexual anatomy: we cover our genitalia with undergarments (usually) we do not see genitalia on TV or in advertisements some men worry about the size of their penis and some women worry about the size of their breasts we alter sexual anatomy surgically (e.g., breast implants) Given such focused attention and concern, let us first examine the human sexual anatomy and see what all the fuss is about.

3. Male Sexual Anatomy held in the scrotum suspended by the spermatic cord –blood vessels, nerves, vas deferens, cremaster muscle The easiest way to cover male sexual anatomy is to follow the path taken by sperm: Testes (from Latin word testis - “to witness or testify”)

4. Male Sexual Anatomy (con’t) seminiferous tubules –produce sperm in tubules –form lobules Leydig (interstitial) cells –produces 95% of all testosterone –produces low levels of estrogen epididymis –stores sperm until maturity with help of “nurse cells” –stores sperm until ejaculation Within the testis:

5. Special Feature – Testis Self-Examination

6. Male Sexual Anatomy (con’t) vas deferens seminal vesicles –secretes 60% of total semen volume –nourish sperm in the form of “fructose” –neutralize acid in the vagina ejaculatory ducts Genital Ducts and Semen-producing Glands:

7. Male Sexual Anatomy (con’t) prostate gland –alkaline fluid (20-30% of semen volume) is released into the urethra at ejaculation and mixed with seminal fluid and sperm Cowper’s Gland –secretes slippery alkaline fluid to neutralize urine remaining in urethra

8. Male Sexual Anatomy (con’t) The penis: shaft – consists of three cylinders of spongy tissue: –corpora cavernosa - two cylinders on the top-side of penis –corpus spongiosum - underside of penis surrounding the urethra

9. Male Sexual Anatomy (con’t) Each cylinder contains irregularly-shaped cavities called “sinusoids.” When aroused, blood vessels in penis dilate and cavities fill with blood, thus producing an erection.

10. Male Sexual Anatomy (con’t) glans (i.e., the “head”) - bulbous end of the corpus spongiosum. –corona - rim at base of the glans –frenulum - skin where glans meets body of penis (underside) foreskin (prepuce) - fold of skin at birth; covers most of glans.

11. Circumcision Circumcision – removal of the foreskin. Why are males circumcised?

12. Myth of Size Some men may be concerned with the size of their penis. Many devices (e.g., Austin Powers and the penis pump), pills, and treatments (e.g., tying weights to penis) have been used. In a flaccid state, the average size is 3.5” x 1” diameter; in erect state, the average is 6.5” x 1.5” diameter. Because of the elasticity of the vagina, length probably plays no role in increased vaginal/clitoral stimulation. The thickness of a penis, however, may indirectly stimulate the clitoris more.

13. Female Sexual Anatomy The easiest way to cover female sexual anatomy is to follow the path taken by an ovum (i.e., egg): ovaries – female gonads (testes in males) –secrete estrogens and androgens –produce ova fallopian tube – curved tube connected to uterus –fimbria (finger-like projections at entrance) –cilia (hair-like structures help transport ovum

14. Female Sexual Anatomy (con’t) uterus (or womb) – is the organ of gestation. composed of three layers (innermost to outer): –endometrium –myometrium –perimetrium cervix – lower portion of uterus connecting to vagina Cervical cancer occurs most frequently in women who begin having sex at a young age, numerous sexual partners, and certain STDs (especially genital herpes and papilloma – genital warts). Yearly Pap tests help early detection.

15. Female Sexual Anatomy (con’t) vagina – thin-walled, muscular tube –increases in length and width during arousal and childbirth –becomes blood-engorged during arousal –few touch and pressure receptors (except G-Spot) Gräfenberg Spot - located in front of anterior wall of vagina, midway between pubic bone and cervix

16. Female Sexual Anatomy (con’t) mons pubis (mons veneris) - fatty tissue covered with pubic hair labia majora (outer lips) - counterpart of scrotum labia minora (inner lips) and forms clitoral hood (prepuce) clitoris - most sensitive part of female sexual anatomy vulva (or pudendum – includes all external genitals

17. Female Sexual Anatomy (con’t) clitoris - most sensitive part of female sexual anatomy hymen - connective tissue covering all or part of vaginal opening in many virgins Four different types: annular - forming a circle septate - divided or having a septum cribiform - perforated by tiny holes imperforate - no apparent opening

18. Female Sexual Anatomy (con’t) Pubococcygeus Muscle (PC muscle) - muscle surrounding vaginal entrance and walls –forms the floor of pelvic cavity and supports the uterus, vagina, bladder, urethra, and rectum –involved in orgasmic contractions –Kegel exercises can increase pleasure

19. Female Sexual Anatomy (con’t) breasts - fatty tissue forms the bulk of the breast –stimulation can cause arousal and orgasm in some women –external structures include the nipple and areola –internal structures include the milk ducts and mammary glands

20. Special Feature – Breast Self-Examination One is eight women in the U.S. will get breast cancer by age 85. With early detection, however, the survival rate is quite high (94% of women with localized breast cancer survive for at least five years after treatment). Given the rate of breast cancer, women should begin conducting monthly breast self-examinations. By age 40, women are advised to have a mammogram every other year. By age 50, mammograms should be taken annually.

21. Glands and Hormones Exocrine Glands - The exocrine glands secrete substances into ducts that empty into body cavities or onto body surfaces. Some examples include: –sweat glands –salivary glands –mammary glands –digestive glands Endocrine Glands - The endocrine glands secrete hormones directly into the bloodstream. –Hormones are carried by the bloodstream throughout the body to internal organs, other glands, and the central nervous system (CNS) The human body has two types of glands: exocrine and endocrine.

22. Glands and Hormones (con’t) Adrenal Glands - secrete androgens (masculinizing hormones) and estrogens (feminizing hormones) Pituitary Gland - sometimes called the “master gland” because it can stimulate other endocrine glands to produce their hormones. It secretes a variety of hormones as well: –growth hormone –gonadotropins

23. Glands and Hormones (con’t) Gonadotropins - (“gonad changers”) –follicle-stimulating hormone (FSH) - induces ovarian follicles to mature or sperm production at puberty –luteinizing hormone (LH) - stimulates ovulation or secretion of androgen from testes prolactin - stimulates mammary glands to produce milk oxytocin - causes release of milk from mammary glands Hypothalamus - controls the pituitary through blood vessels connected to the pituitary.

24. Feedback loop of Hormone Functioning Hormones work via a continuous feedback loop. A drop in level of one hormone will be detected by one gland and cause another gland to secrete more of the hormone until normal levels are reached. The Menstrual Cycle Consists of five phases which last between 23-32 day (shorter or longer cycles are considered “irregular”). Menarche is the first menstrual cycle. Click to view an animated explanation of the menstrual cycle.animated explanation

25. Feedback loop (con’t) Follicular Phase (7-19 days long) –the decrease in estrogen and progesterone just prior to menstruation makes ovaries sensitive to FSH –FSH causes 6-12 follicles to begin growing and their cells start to secrete estrogen –around 12 days, high levels of estrogen cause the hypothalamus to release GnRH which stimulates a surge in the production of LH.

26. Feedback loop (con’t) Ovulation - around 18 hours after the surge of LH, a mature follicle ruptures and releases its ovum (ovulation) into the fallopian tube Luteal Phase (8-10 days long) - ruptured follicle (the corpus luteum or “yellow body”) secretes progesterone which stimulates growth of glands in the endometrium in order to prepare for a fertilized egg

27. Feedback loop (con’t) Premenstrual Phase (4-6 days long) - in the absence of a fertilized egg, the corpus luteum begins to disintegrate causing a decrease in progesterone and estrogen Menstruation (3-7 days long) - the decrease in progesterone and estrogen results in the disintegration and discharge of part of the endometrium