Chapter 5 Male Sexual Anatomy & Physiology

1. Chapter 5Male Sexual Anatomy & Physiology

2. The Penis • Nerves, blood vessels, fibrous tissue, and three parallel cylinders of spongy tissue. • There is no bone and little muscular tissue (although there are muscles at the base of the penis) • Terms: • Root, shaft, glans, cavernous bodies, spongy body, foreskin (defined on next slide)

3. The Penis • Penis: consists of internal root, external shaft, & glans. • Root: the portion of the penis that extends internally into the pelvic cavity. • Shaft: the length of the penis between the glans and the body. • Glans: the head of the penis; has many nerve endings. • Cavernous bodies: the structures in the shaft of the penis that engorge with blood during sexual arousal. • Spongy body: a cylinder that forms a bulb at the base of the penis, extends up into the penile shaft, and forms the penile glans. Also engorge with blood during arousal. • Foreskin: a covering of skin over the penile glans.

4. Male Sexual Anatomy (cont.) Internal structure of the penis: top view (internal, in pelvic cavity) (between glans and the body) (engorge with blood during arousal) (head of the penis; lots of nerve endings) (expands to form the glans) Fig 5.1a Interior structure of the penis: (a) view from above.

5. Internal structure of the penis:cross-section Fig 5.1b Interior structure of the penis: (b) cross section of the penis

6. External penile structures • Corona: the rim of the penile glans • Frenulum: thin strip of skin connecting the glans to the shaft on the underside of the penis Both are highly sensitive areas to the touch Fig 5.2 This figure, a view of the underside of the penis, shows the location of the corona and frenulum—two areas on the penis that harbor a high concentration of sensitive nerve endings.

7. Scrotum and testes • Scrotum (or scrotal sac): • Pouch of skin that encloses the testes • 2 chambers inside scrotum; each contains one testis • Two layers: skin layer and muscle layer (tunica dartos) • Normally hangs loosely from body wall • cold temperatures and sexual stimulation will cause it to move closer to the body. • Testis • Male gonad inside scrotum that produces sperm and sex hormones • Spermatic cord • A cord attached to the testis inside the scrotum that contains the vas deferens, blood vessels, nerves, and muscle fibers

8. Scrotum and testes (external) Spermatic cord (inside) Fig 5.3 The scrotum and the testes. The spermatic cord can be located by palpating the scrotal sac above either testicle with thumb and forefinger.

9. Internal structures of the scrotum (contains vas deferens, blood vessels, nerves, and cremasteric muscle) (sperm-carrying tube) (muscle fibers that control the position of the testis in the scrotal sac) (where sperm mature and are stored temporarily) Fig 5.4 Internal structures of the scrotum. This illustration shows portions of the scrotum cut away to reveal the cremasteric muscle, spermatic cord, vas deferens, and a testis within the scrotal sac.

10. Internal structures: the Testes • Two functions: 1) Secrete male hormones 2) Produce sperm: testes must hang below body for them to be at the proper temperature for sperm production. • Asymmetry is typical: More commonly, the left testis hangs lower than the right testis b/c the left spermatic cord is usually longer than the right. • Development • Form inside the abdominal cavity and during fetal development migrate to the scrotum. • cryptorchidism: undescended testis • Affects 3-4% of male infants and 30% of premature male infants. • May resolve on its own or may require surgery. testis

11. Structures inside the testis • Seminiferous tubules • Thin, highly coiled structures where sperm production occurs. • Interstitial cells • Major source of androgens • Located between seminiferous tubules • Epididymis • Site of sperm maturation • Runs along back of testis • Vas deferens • Sperm-carrying tube • Begins at the testis and ends at the urethra.

12. Cross-section of seminiferous tubule Interstitial cells: secrete androgens Spermatogenic cells: produce sperm Immature sperm

13. Vas deferens • After the sperm mature in the epididymis, they drain into the vas deferens • Vas deferens travels up through scrotum inside spermatic cord, along top of bladder, and deposits sperm into urethra • Vasectomy: male sterilization procedure that involves removing a section from each vas deferens Vas deferens

14. Overview: male sexual anatomy Fig 5.6 Male sexual anatomy: A cross-section side view of male reproductive organs.

15. Seminal vesicles • Small glands adjacent to end of vas deferens • Secrete an alkaline (basic) fluid • Has high sugar content that helps sperm motility by giving them a lot of energy • This fluid is the greatest portion of the volume of semen released during ejaculation Seminal vesicle

16. Prostate gland • Walnut-sized gland at the base of the bladder. • Secrete milky, alkaline (basic) fluid that makes up about 30% of volume of semen released during ejaculation. • Alkalinity helps counteract the acidity of the male urethra and the female vaginal tract to help sperm survive. Prostate gland

17. Cowper’s glands • Pea-sized glands that attach to urethra just below prostate gland • Secrete an alkaline fluid during sexual arousal. • Not the same as semen; released before ejaculation (in slang, often called “pre-cum.”) • Thought to counteract acidity of male urethra and help lubricate flow of semen through the urethra. • May possibly contain a few active, healthy sperm (a potential problem for the withdrawal method of birth control). Cowper’s gland

18. Semen • Volume per ejaculation: about 1 teaspoon • Depends on length of time since last ejaculation, duration of arousal before ejaculation, and age. • Fluids from: • Seminal vesicles (almost 70%) • Prostate gland (about 30%) • (possibly) a tiny bit of fluid from Cowper’s glands depending on time of secretion • Sperm • Between 200 - 500 million sperm per ejaculation • Only about 1% of total volume.

19. Analagous structures in male and female sexual anatomy(more on this will be covered in Chp. 3) Male Glans Foreskin Shaft Scrotal sac Testes Female Clitoris Clitoral hood Labia minora Labia majora Ovaries

20. Group activity: male A & P flashcards One side: name of term Other side: definition, function, location TERMS: Penis Testes Glans Seminiferous tubule Foreskin Epididymis Cavernous bodies Vas deferens Spongy body Seminal vesicles Corona Prostate gland Frenulum Cowper’s glands Scrotum

21. Discussion question: (5-A) • What are some slang terms for male genitalia? Keep track of how many terms your group knows. • Are these terms positive or negative? • Why do people tend to use “nicknames” for parts of the male sexual anatomy? • What do the nicknames we use for male genitalia say about our thoughts or opinions about male genitalia?

22. Kegel exercises: Strengthen the pelvic floor muscles in men and women (see p. 85, 114) • Exercises originally developed to treat incontinence • Enhance sexual enjoyment • Women: increased sensitivity during intercourse, possibly, stronger orgasms • Men: stronger orgasms, better ejaculatory control, increased pelvic sensation during arousal • Locate the correct muscles by trying to stop the flow of urine while urinating • Kegel exercises include both short contractions/ relaxations as well as longer contractions held for several seconds • Exercises should be done 2-3 times a day

23. erect flaccid Male sexual function: Erection • Brain sends message that causes relaxation of the arteries that supply blood to the cavernous and spongy bodies in the penis. • Veins that drain blood away from cavernous and spongy bodies can’t keep up with blood inflow, producing an erection. • Erection is maintained by pressure of spongy and cavernous bodies against the skin, partially closing off the veins. • Involves both psychological and physiological factors

24. How blood inflow helps maintain erection • Inside the penis: like a tube within a tube • When the inner tube fills with blood and expands, it fills the space between the tubes and blocks the outflow of blood, helping to maintain erection.

25. Ejaculation • Ejaculation: the process by which semen is expelled through the penis outside the body. • Ejaculation is a separate process from orgasm, and the two may not always occur simultaneously. • It is possible for men to experience multiple orgasms w/o ejaculation. • 2 phases (see next slides for details): 1) Emission phase: semen collects in the urethral bulb • This stage is usually sensed by the man as the “point of no return” 2) Expulsion phase: semen is expelled

26. (like a balloon) Emission phase of ejaculation (phase 1) • Contractions in the prostate, seminal vesicles, and vas deferens force secretions into urethral bulb. • Both the internal and external urethral sphincters close, trapping semen in the urethral bulb

27. Expulsion phase of ejaculation (phase 2) • Collected semen is expelled out of the body by rhythmic contractions of muscles surrounding the urethral bulb and also on the urethra. • External urethral sphincter relaxes to allow semen out; internal urethral sphincter stays contracted to prevent the escape of urine.

28. Retrograde ejaculation: when semen is expelled into the bladder instead of out of the penis • Due to reversed function of the two urethral sphincters (internal sphincter relaxes and external sphincter contracts instead of the other way around). • Can result from prostate surgery, illness, birth defect, tranquilizers. • Not harmful, but would cause sterility and could be a sign of an underlying health problem. • Nocturnal emission: involuntary ejaculation during sleep • Also known as a wet dream • Mechanism not fully understood

29. Penis size • More men are concerned about penis size than their female partners are. • Much more variation in flaccid penis size than in erect penis size. • Comparisons in the locker-room don’t mean much. • “Bigger is better” isn’t always the case • Most women achieve orgasm through clitoral, not vaginal, stimulation • Obsession w/penis size results from a “penis-centered” idea of sex--great sex can happen w/no penis at all! • What is “average” length anyway? • 5.1 - 5.7 inches (much less than you see or hear about in adult movies or erotic literature).

30. Penile Augmentation (phalloplasty) • Penis lengthening: involves severing of ligaments that attach penile root to pelvic bone • Part of the penis normally inside the body drops down • Penile girth enhancement: usually involves injecting fat from other areas of the body. • Possible dangers and warnings: • Some loss of sensation, scarring, changed angle of erection • Penis could actually end up being shorter due to scar tissue causing penis to retract further into body • Injected fat can be rejected by the body, causing a lumpy, misshapen appearance • Most men who elect to have phalloplasty in fact do not have undersized penises.

31. Circumcision • Circumcision: surgical removal of the foreskin of the penis.

32. Country % circumcised U.S. 55 - 60% Canada <15% Australia 10 - 20% Europe 5 - 15% Ethnic group % circumcised Caucasian 81% Latino 54% African-American 65% Rates of circumcision • International differences: • Ethnic differences

33. Circumcision: medical perspective • Medical benefits • Reduced rate of penile cancer (from about 6 in 100,000 to about 1 in 100,000) • If not properly cleaned, the area under the foreskin can harbor infection-causing organisms, contributing to increased susceptiblity to UTIs (urinary tract infections) and STDs • Most of the medical benefits of circumcision can probably be realized in uncircumcised men with proper hygeine • Medical risks • Effects on sexual functioning are unclear • Possible surgical complications (bleeding, infection, etc.) • Pain during circumcision • Can’t use general or narcotic anesthesia on infants • Correlation btwn. infants circumcised w/o anesthesia and a stronger pain response to subsequent vaccination.

34. Circumcision: medical perspective • American Academy of Pediatrics position: • There are potential benefits but also potential risks. • Procedure is not medically essential. • Decision is left up to parents. • If parents decide to circumcise, they should ask for analgesia to be used. (1999; reaffirmed in 2005)

35. Circumcision and sexual functioning • Difficult subject to research • Circumcision most commonly occurs at birth, so research subjects rarely have experienced “before” vs. “after” • Those men who are circumcised as adults often have a medical problem that necessitates circumcision. • Some reports have indicated that the glans of the penis may be less sensitive in circumcised men. • May or may not influence rate of premature ejaculation. • Two reports that surveyed women who had intercourse with circumcised men and uncircumcised men suggested that circumcision may exacerbate vaginal dryness and reduce clitoral stimulation during intercourse.

36. Discussion question: (5-B) PART 1: Which of the research methods described in Chapter 2 might be effective to demonstrate whether or not being circumcised affects sexual response and pleasure (male and female)? What kind of research design would you use in such a study? PART 2: If you had a newborn son, would you have him circumcised? Why or why not?

37. Male Genital Health Concerns • Urology: the medical specialty focuses on male reproductive health issues, and urinary tract health problems in both sexes. • General health issues: • Cleanliness can reduce infections and build-up of smegma • Smegma: “cheesy” substance of glandular secretions and skin cells that sometimes accumulates under the foreskin. • Some men can develop a reaction to vaginal secretions. • Injuries: • use of “cock rings” for > 30 min. can cut off blood supply and injure penile tissue • Masturbation with vacuum devices can cause severe injuries • Penile “fracture” can occur during intercourse--involves rupture of the cavernous bodies when penis is erect. • Condoms offer protection against STIs (more on this in Chp. 17)

38. Penile cancer • Penile cancer: • One of the rarest forms of cancer (approx. 1300 cases in the U.S. each year) • Survival rate is less than half unless it is caught early. • Usually begins as a small, painless sore on the glans or foreskin that eventually changes into a cauliflower-like mass that is chronically inflamed and tender. • Risk factors: age over 50, history of multiple partners and STDs (especially herpes), poor genital hygiene, long history of smoking. • Left untreated, will eventually destroy the penis and spread to lymph nodes and beyond.

39. Testicular cancer • Testicular cancer: • Only 1% of cancers that occur in males. • One of the most common cancers that occur in young men (age 15-34); half of cases are in men younger than 35. • Early stage: small mass within the testis that feels hard and irregular to fingertips; may be as small as a pea and may be painless or tender to the touch. • Some other symptoms reported include fever, dull ache in groin, feeling of heaviness in testes, tender breasts and nipples. • Some types of testicular cancer grow more rapidly than other cancers; therefore, very important to catch it early. • If caught early, survival rate is >90%.

40. Prostate Health Care Issues • Prostatitis: when prostate becomes enlarged and inflamed, usually due to infection • Usually treated w/antibiotics. • Benign prostatic hyperplasia • Increase in the size of the prostate gland • Increasingly common as men age • Enlarged gland can put pressure on urethra and decrease urine flow; can be treated w/medication.

41. Prostate Cancer • 200,000 men diagnosed and 30,000 die each year in U.S. • One of the most frequentlly diagnosed cancer in men, and second leading cause of cancer death (after lung cancer) • Associated factors: old age, family history, prior history of STDs, diet high in saturated fats. • Incidence is 60% higher in African Amerian men than white men, and survival rate is lower--reasons not known. • Compared with white Americans, mortality is 40% lower among Asian American men and 35% lower in Latino American men.

42. Prostate Cancer: Symptoms & diagnosis • Symptoms are similar to prostatitis: • Pelvic and lower back pain, urinary complications • May be no symptoms in early stages • Screening and diagnosis • Physical examination: physician inserts finger into rectum to feel for lumps in prostrate gland. • Blood test: examines levels of PSA (prostate-specific antigen) • Normal PSA levels are <4 nanograms per ml of blood. • Detection of prostate cancer is not precise, and there is controversy about whether screening is even beneficial.