Presentation on theme: "Chapter 4: Male Sexual Anatomy & Physiology"— Presentation transcript:
1 Chapter 4: Male Sexual Anatomy & Physiology Bio 27: September 17, 2012Chapter 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 rootHead of the penis is called the glansRemainder of penis is the shaftRemind you of anything?
3 The penis: external anatomy The glans of the penis is covered by a loose layer of skin called the foreskinThe 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 areasurethral opening is site of urine and semen exitJews & Muslims but also ancient Egyptians (circumcised mummies)
4 The scrotumScrotum: pouch with two chambers for each of two testicles or testesHas two layers:skin layer: skin is darker than on rest of body and becomes covered with hair at puberty; analogous to labia majora in womentunica dartos: muscle layerPulls sac closer to body in cold temperatures or with sexual stimulationSpermatic cord: suspends testes in scrotumVas deferens: transports sperm
5 The testes: function Seminiferous tubules: site of sperm production Sperm travel from there to the epididymis, where they are storedInterstitial cells between seminiferous tubules make most of the body’s testosteroneSperm 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 brainArteries leading to the three erectile layers of the penis expandBloodflow rapidly increasesCapacity for erection is present at birthCommon and natural for infant boys to have erections during sleep, diaper changes, or stimulation from clothingCommon 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 contractSpinal reflex: can ejaculate even if paralyzed from the waist down; contractions move fluid into urethral bulbEmission phase feeling that ejaculation is inevitableExpulsion often happens as a few waves of contraction; lasts 3–10 seconds usuallyRetrograde ejaculationNocturnal ejaculation
8 Ejaculatory problemsRetrograde ejaculation: if internal urethral sphincter fails to contract, semen can enter the bladderSometimes happens after prostate surgerySome medications can also causeNot harmful but impairs fertilityNocturnal emissions: “wet dreams,” mechanism not understoodErotic dreams probably not entirely responsible for nocturnal emissions; common in teens
9 Semen Seminal Vesicle Prostate Gland Cowper’s Glands Secretes 70% of seminal fluidProstate GlandSecretes 30% of seminal fluidCowper’s GlandsSecretes fluid before ejaculationsMay contain active, healthy spermSemen (seminal fluid)Volume is about 1 teaspoon200 to 500 million sperm
10 Kegels for menMuscles at the base of the penis that help control the expulsion phase of ejaculation are similar to the pelvic floor muscles in womenKegel exercises can help improve strength and have been associated with stronger and more pleasurable orgasms, better ejaculatory control and increased pelvic sensation during sexual arousalYMMVlocate muscles by stopping flow of urine; if do a Kegel while not urinating will slightly move penissqueeze and relax muscles 15 times 2x daily; gradually increase to 60 at a time twice dailythen 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 virilityErect penises show less variation than flaccidDoes 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 excitingASSUME 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 augmentationPhalloplasty: surgery to increase the length or girth of the penisLength 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 outsideWidth can be increased by injecting fat or other tissue into the penisCan 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 penisMen who undergo procedures often have penises not smaller than average
13 Genital Retraction Syndrome (Koro) Belief that one’s genitals are shrinking or disappearingPsychological not medical disorder!“Outbreak” in Singapore in 1967 caused thousands of men to visit the hospital, many with clamps and weights on their penisesSometimes associated with accusations of witchcraft or sorcery
14 Other Concerns about Sexual Functioning Phimosis: extremely tight foreskin, prevents glans from being fully exposed during sexWithout phimosis, circumcision makes no difference in contact during intercourse
17 Male Genital Health Penis Health-Care Issues CleanlinessSmegma: can serve as a breeding ground for infections and have an unpleasant odorReaction to vaginal secretionsCan sometimes develop eczema-like reaction; can be avoided with condom usePenile cancerRare: only 1300 men develop per year, but deadlyEarly detection is keyRisk factors include: old age, history of multiple sexually transmitted diseases, especially genital warts, poor hygiene, being uncircumcised, phimosis, and smoking
18 Penis injuriesCock 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 intercoursepenile fracture can be treated with rest & ice, sometimes need surgery
19 Prostate cancerSecond most common cancer in American males (after skin cancer)Risk factors are: old age, family history, high-fat diet, African-American race218,000 U.S. men are diagnosed each year and 28,000 U.S. men die from it each yearCan be detected with a blood test (somewhat controversial) or with a physical examination (digital rectal examination)
20 PSA testProstate-specific antigen test is a blood test that detects a chemical often elevated in prostate cancerMany false positive resultsFor 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 ANONYMOUSLYIf you don’t want to answer a question, write “No questions” on your cardI will answer these in class next time