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Chapter 4: Male Sexual Anatomy & Physiology

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1 Chapter 4: Male Sexual Anatomy & Physiology
Bio 27: September 17, 2012 Chapter 4: Male Sexual Anatomy & Physiology

2 The Penis: internal anatomy
Consists of nerves, blood vessels, fibrous tissue & spongy tissue; no bones! Interior portion of the penis is the root Head of the penis is called the glans Remainder of penis is the shaft Remind you of anything?

3 The penis: external anatomy
The glans of the penis is covered by a loose layer of skin called the foreskin The corona is a ridge of tissue around the glans of the penis; it along with the frenulum, a strip of skin that attaches the glans to the shaft on the underside of the penis, are among the most sensitive areas urethral opening is site of urine and semen exit Jews & Muslims but also ancient Egyptians (circumcised mummies)

4 The scrotum Scrotum: pouch with two chambers for each of two testicles or testes Has two layers: skin layer: skin is darker than on rest of body and becomes covered with hair at puberty; analogous to labia majora in women tunica dartos: muscle layer Pulls sac closer to body in cold temperatures or with sexual stimulation Spermatic cord: suspends testes in scrotum Vas deferens: transports sperm

5 The testes: function Seminiferous tubules: site of sperm production
Sperm travel from there to the epididymis, where they are stored Interstitial cells between seminiferous tubules make most of the body’s testosterone Sperm are produced in the seminiferous tubules and transported to the epididymis, which serves as a storage chamber. (b) the cross section enlargement view of the seminiferous tubules shows spermatogenic (sperm-making) cells and the interstitial cells.

6 Function of the Male Anatomy: Erection
Coordinated by the nervous system; ultimately controlled by the brain Arteries leading to the three erectile layers of the penis expand Bloodflow rapidly increases Capacity for erection is present at birth Common and natural for infant boys to have erections during sleep, diaper changes, or stimulation from clothing Common to undergo erection during sleep—not necessarily linked to sexual dreams! Erections may be psychogenic (from the mind) or physiogenic (from the body) thoughts can enhance erection or postpone ejaculation

7 Ejaculation Spinal reflex happens in two phases:
Emission: fluid from the prostate, seminal vesicles and vas deferens enters the urethral bulb; urethral sphincters simultaneously close; “point of no return” Expulsion: semen expelled when muscles around urethral bulb & in the root of the penis contract Spinal reflex: can ejaculate even if paralyzed from the waist down; contractions move fluid into urethral bulb Emission phase feeling that ejaculation is inevitable Expulsion often happens as a few waves of contraction; lasts 3–10 seconds usually Retrograde ejaculation Nocturnal ejaculation

8 Ejaculatory problems Retrograde ejaculation: if internal urethral sphincter fails to contract, semen can enter the bladder Sometimes happens after prostate surgery Some medications can also cause Not harmful but impairs fertility Nocturnal emissions: “wet dreams,” mechanism not understood Erotic dreams probably not entirely responsible for nocturnal emissions; common in teens

9 Semen Seminal Vesicle Prostate Gland Cowper’s Glands
Secretes 70% of seminal fluid Prostate Gland Secretes 30% of seminal fluid Cowper’s Glands Secretes fluid before ejaculations May contain active, healthy sperm Semen (seminal fluid) Volume is about 1 teaspoon 200 to 500 million sperm

10 Kegels for men Muscles at the base of the penis that help control the expulsion phase of ejaculation are similar to the pelvic floor muscles in women Kegel exercises can help improve strength and have been associated with stronger and more pleasurable orgasms, better ejaculatory control and increased pelvic sensation during sexual arousal YMMV locate muscles by stopping flow of urine; if do a Kegel while not urinating will slightly move penis squeeze and relax muscles 15 times 2x daily; gradually increase to 60 at a time twice daily then can do “long Kegels” holding for a count of 3

11 Concerns about Sexual Functioning: Penis Size
Penis size is seen as a symbol of virility Erect penises show less variation than flaccid Does size matter? What are some things you’ve heard about penis size? not related to hand or foot size or race; no evidence that women prefer bigger or find more exciting ASSUME THAT YOU ARE ASSIGNED TO DEBATE WHETHER A CAUSE-AND-EFFECT RELATIONSHIP EXISTS BETWEEN PENIS SIZE AND SEXUAL SATISFACTION OF WOMEN DURING PENILE–VAGINAL INTERCOURSE. WHICH POSITION WOULD YOU ARGUE? WHAT EVIDENCE WOULD YOU USE TO SUPPORT YOUR POSITION?

12 Penile augmentation Phalloplasty: surgery to increase the length or girth of the penis Length can be increased by making an incision at the base of the penis, severing ligaments that attach root to the pelvic bone, causing the root to be on the outside Width can be increased by injecting fat or other tissue into the penis Can be dangerous and disfiguring (scars, lumps) No evidence that creams and pills advertised online work; they may enhance erection by increasing blood flow to the penis Men who undergo procedures often have penises not smaller than average

13 Genital Retraction Syndrome (Koro)
Belief that one’s genitals are shrinking or disappearing Psychological not medical disorder! “Outbreak” in Singapore in 1967 caused thousands of men to visit the hospital, many with clamps and weights on their penises Sometimes associated with accusations of witchcraft or sorcery

14 Other Concerns about Sexual Functioning
Phimosis: extremely tight foreskin, prevents glans from being fully exposed during sex Without phimosis, circumcision makes no difference in contact during intercourse

15 Sexual functioning viagra cialis levitra

16 Sexual functioning

17 Male Genital Health Penis Health-Care Issues
Cleanliness Smegma: can serve as a breeding ground for infections and have an unpleasant odor Reaction to vaginal secretions Can sometimes develop eczema-like reaction; can be avoided with condom use Penile cancer Rare: only 1300 men develop per year, but deadly Early detection is key Risk factors include: old age, history of multiple sexually transmitted diseases, especially genital warts, poor hygiene, being uncircumcised, phimosis, and smoking

18 Penis injuries Cock rings can sustain erection, but can also damage or even destroy penile tissue by cutting off blood supply! Penis “fracture” can occur when cavernous bodies are ruptured while erect, frequently during intercourse penile fracture can be treated with rest & ice, sometimes need surgery

19 Prostate cancer Second most common cancer in American males (after skin cancer) Risk factors are: old age, family history, high-fat diet, African-American race 218,000 U.S. men are diagnosed each year and 28,000 U.S. men die from it each year Can be detected with a blood test (somewhat controversial) or with a physical examination (digital rectal examination)

20 PSA test Prostate-specific antigen test is a blood test that detects a chemical often elevated in prostate cancer Many false positive results For many who actually do have prostate cancer, a “watch and wait” approach is recommended

21 Anonymous question box
Write down any questions about male or female sexual anatomy you may have ANONYMOUSLY If you don’t want to answer a question, write “No questions” on your card I will answer these in class next time

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