Discussion question: (4-A) Let’s Talk about the Parts of the Penis • What are some slang terms for male Chapter 4 genitalia? Keep track of how many terms your group knows. ! • Are these terms positive or negative?! Male Sexual • Why do people tend to use “nicknames” Anatomy & Physiology 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? ! The Penis Internal structure of the penis: top view The Penis (internal, in • Penis: consists of internal root, external shaft, & glans.! (between glans and the body) pelvic cavity) Male Sexual Anatomy (cont.) • Root: portion of the penis that extends internally into the pelvic cavity.! • Shaft: length of the penis btwn. glans and body wall.! • Glans: head of the penis; has many nerve endings.! • Cavernous bodies: two tube-like structures in shaft of the penis that engorge with blood during arousal.! • Nerves, blood vessels, fibrous tissue, and three • Spongy body: cylinder in shaft, extends to form the parallel cylinders of spongy tissue.! penile glans. Also engorges with blood during arousal.! (engorge with blood (head of the (expands during arousal) • There is no bone and little muscular tissue penis; lots of to form • Foreskin: a covering of skin over the penile glans.! nerve endings) the glans) (although there are muscles at the base of the penis)! Fig 5.1a Interior structure of the penis: (a) view from above. External penile structures “Man, you’re small. There ain’t no Penis size man or woman out there who will ever get pleasure from that thing.” • What is “average” length anyway?! • Corona: the rim of the – 5.1 - 5.7 inches (much less than you see or hear about in adult movies or penile glans! Think/write/share:! erotic literature). • Frenulum: thin strip of skin connecting the glans to the Is bigger better?! 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. Penis size Penis size Penile Augmentation (phalloplasty) • Much more variation in flaccid penis size than in erect • Penis lengthening: involves severing of ligaments that attach • More men are concerned about penis size than their penile root to pelvic bone! female partners are.! penis size. ! – Comparisons in the locker-room don’t mean much.! – Inside part of the penis drops down! • “Bigger is better” isn’t always the case! • Penile girth enhancement: usually – Most women achieve orgasm through clitoral, not vaginal, injecting fat from other areas of the body.! stimulation! • Possible dangers and warnings:! – Obsession w/penis size results from a “penis-centered” idea of – Some loss of sensation, scarring, changed sex--great sex can happen w/no penis at all! ! 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.! Scenes from “Private Dicks” Scrotum and testes Scrotum and testes (external) • Scrotum (or scrotal sac):! – Pouch of skin that encloses the testes! • 2 chambers inside scrotum; each contains one testis! – Normally hangs loosely from body wall! • cold temperatures and sexual stimulation will cause it to move closer to the body.! Spermatic cord" • Testis! (inside)" – 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! 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. Internal structures of the scrotum Internal structures: the Testes Structures inside the testis •! Two functions:! •! Seminiferous tubules! (contains vas deferens, 1) Secrete male hormones! –! Thin, highly coiled structures where blood vessels, nerves, and cremasteric muscle) 2) Produce sperm: testes must hang below sperm production occurs.! the body to be at the proper temperature •! Interstitial cells! for sperm production.! (sperm-carrying tube) –! Major source of androgens ! –! Located between seminiferous •! Development! tubules! (muscle fibers that control testis the position of the testis –! First form inside the abdominal cavity! in the scrotal sac) (where sperm mature and ! ! are stored temporarily) • Epididymis –! During fetal development they migrate to the scrotum! –! Site of sperm maturation! –! cryptorchidism: undescended testis ! –! Runs along back of testis! •! Affects 3-4% of male infants and 30% of premature male infants.! •! Vas deferens! 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 •! May resolve on its own or may require surgery.! –! Sperm-carrying tube! a testis within the scrotal sac. –! Begins at the testis and ends at the urethra.! Cross-section of seminiferous tubule Analagous structures in Vas deferens Interstitial cells: secrete androgens male and female sexual anatomy •! After sperm mature in the (more on this will be covered in Gender Chp.) Vas epididymis, they go deferens into the vas deferens! •! Vas deferens travel up Male! Female! through scrotum inside Glans! Clitoris! spermatic cord, and Foreskin! Clitoral hood! deposit sperm into Shaft! Labia minora! urethra! Scrotal sac! Labia majora! Testes! Ovaries! •! Vasectomy: male sterilization procedure in which both vas deferens are severed, then tied off or blocked so sperm can not flow out into semen! Spermatogenic cells: produce sperm Immature sperm A sperm’s Seminal vesicles Prostate gland long journey •! Walnut-sized gland at •! Pair of small glands adjacent Seminal vesicle to end of vas deferens! the base of the bladder. ! !!Vas deferens Whole journey •! Secrete an alkaline (basic) •! Secretes milky, slightly takes ~75 days! fluid! alkaline (basic) fluid during –! Has high sugar content that ejaculation (~30% of Prostate #! Urethra helps sperm motility by volume of semen)! gland giving them lots of energy! –! Alkalinity helps neutralize the acidity of the male –! This fluid is the greatest urethra and the female vaginal tract to help portion of the volume of sperm survive.! %! semen released during $! ejaculation (~70%)! Seminiferous tubules "! What is the Cowper’s glands Semen “P spot”? •! Pea-sized glands that •! Volume per ejaculation: about 1 teaspoon! •! It’s the prostate! attach to urethra just –! Depends on length of time since last ejaculation, •! Prostate stimulation is below prostate gland! duration of arousal before ejaculation, and age.! performed to:! •! Secrete an alkaline fluid •! Fluids from: !! –! Produce orgasm/pleasure! during sexual arousal –! Seminal vesicles (almost 70%)! –! Prevent/relieve various (before ejaculation, Cowper’s –! Prostate gland (about 30%)! slang term = “pre-cum”)! gland causes of enlarged prostate! –! (possibly) a tiny bit of fluid from Cowper’s glands •! Neutralizes acidity of male urethra and helps depending on time of secretion! lubricate flow of semen through the urethra.! •! Sperm! •! May possibly contain (or wash through) a few –! Between 200 - 500 million sperm per ejaculation! active, healthy sperm (potential problem for the withdrawal –! Only about 1% of total volume.! method of birth control).! Summing up: What causes an erection? How blood inflow helps maintain erection Moving Mature Sperm Out • Brain sends message to blood vessels inside • Inside the penis: like a tube within a tube! cavernous and spongy bodies in the penis to relax – When the inner tube fills with blood and Seminal Vesicles! and dilate (open up).! flaccid erect expands, it fills the space between the tubes • Produce majority of Semen – Fluid w/Sugars, nutrients for sperm (70% of semen by volume)! • Blood vessel dilation cause blo that and blocks the outflow of blood, helping to Prostate Gland! causes lots of blood to maintain erection.! • Produces milky substance to neutralize acid in urethra to help sperm survive (29%)! flow into cavernous and Cowper’s Gland! spongy bodies in the penis! • Produce fluid to lubricate and neutralize acid in urethra before ejaculation (ie pre-cum <1%)! • Blood inflow >>> blood outflow, producing an Vas Deferens! • Smooth muscle moves sperm (<1%) to Urethra! erection.! Epididymis! • Erection is maintained by pressure of spongy and • Sperm Move Here from Seminiferous Tubule! cavernous bodies against the skin! Ejaculation Review: Kegel Exercises—for men too! Emission phase of ejaculation (phase 1) • WHY! • Contractions in the prostate, seminal vesicles, and vas • Ejaculation: the process by which semen is – All: prevent incontinence in older years! deferens force secretions into urethral bulb.! expelled through the penis outside the body.! – All: increase sensation & orgasmic intensity! • Both the internal and external urethral sphincters close, • Ejaculation is a separate process from orgasm, trapping semen in the urethral bulb! – Women: regain urinary control after and the two may not always occur childbirth! simultaneously.! (like a balloon) – Men: increase ejaculatory control! – It is possible for men to experience multiple orgasms w/o ejaculation.! • HOW! • 2 phases (see next slides for details): ! – Locate muscles!