Male sexual anatomy and physiology
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Chapter Four - PowerPoint PPT Presentation

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Male Sexual Anatomy and Physiology. Chapter Four. Agenda. Discuss Male Sexual & Reproductive System Describe Male Maturation Cycle Discuss Male Reproductive and Sexual Health. What do you think about the penis?. On a blank sheet of paper, respond to the following: “The penis is…”

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  • Discuss Male Sexual & Reproductive System

  • Describe Male Maturation Cycle

  • Discuss Male Reproductive and Sexual Health

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What do you think about the penis?

  • On a blank sheet of paper, respond to the following:

    “The penis is…”

  • Do not put your name on the paper, but turn it in.

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External Sex Organs

Internal Sex Organs

Other Sex Organs

The Male Sexual and Reproductive System

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External Sex Organs

  • Boys are typically more comfortable with their genitalia than girls

    • Testes are visible (ovaries are internal)

    • Penis is typically held during urination

  • External sex organs

    • Penis

    • Scrotum

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The Penis

  • Contains urethra for urine and semen transport

  • Becomes erect to better penetrate the vagina and deposit sperm near the os

  • No bone, little muscle

  • Composed of 3 cylinders of erectile tissue

    • Corpora cavernosa (2)

    • Corpus spongiosum (contains the urethra)

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The Glans Penis

  • The conelike end of the penis

    • Corona

    • Frenulum

    • Meatus

  • Sensitive to stimulation

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The Glans Penis

  • Foreskin is a fold of skin that can cover part or all of the glans; retracts over the corona during an erection

  • Circumcision – surgical removal of the foreskin; most common male surgery in the U.S.

    • Religious/cultural ritual

    • Health reasons

    • Medical value is questionable

    • Women report greater sexual satisfaction with partner’s who have not been circumcised (O’Hara & O’Hara, 1999)

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Class Discussion

  • Male Circumcision is the most common male surgical procedure in the U.S. but it doesn’t seem to be medically necessary.

    • Why do you think it remains so common?

  • Discuss the finding from O’Hara & Hara (1999) which reported that women experience greater sexual satisfaction with men who have not been circumcised.

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The Root of the Penis

  • Extends into the body below the pubic bone

  • Attached to internal pelvic muscles and can be felt in the perineum

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  • Any type of stimulation perceived as sexual can cause an erection; spinal reflex

  • Erection also occurs during REM, possibly to keep the penis supplied with blood

  • Nerve fibers open the arteries of the penis to allow blood to flow into the 3 cylinders

  • Veins compress to prevent exit of blood

  • Flaccid state returns when arteries constrict and the veins open to allow blood to flow out

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The Scrotum

  • Loose, wrinkled pouch beneath the penis containing the testicles

  • Lightly covered with pubic hair

  • Functions to keep the testicles 3°C cooler than the body’s temperature to keep sperm viable

    • Contains sweat glands

    • Cremaster muscle moves the scrotum closer to or farther from the body (protects)

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Vas deferens

Seminal vesicles

Prostate gland

Cowper’s glands

Internal Sex Organs

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The Testicles

  • Two egg-shaped glands in the scrotum

  • 2 inches long, 1 inch diameter

  • Typically one (usually the left) hangs a bit lower to allow sliding past rather than compression

  • 2 primary functions:

    • Testosterone production

    • Spermatogenesis (a/k/a sperm production)

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Testosterone Production

  • Testosterone is the most important male hormone

  • Interstitial, or Leydig, cells in the testicles produce testosterone out of cholesterol

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  • Seminiferous tubules produce and store sperm

  • Sertoli cells (in the tubules) provide nutrition for the development of sperm

  • Sperm production takes 72 days, but is constant and each male produces about 300 million sperm a day

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The Ejaculatory Pathway

  • Ejaculation – physiological process where seminal fluid is powerfully expelled from the penis

  • Pathway organs:

    • Vas deferens

    • Seminal vesicles

    • Prostate gland

    • Cowper’s glands

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The Ejaculatory Pathway

  • Vas deferens – 18-inch tube that carries sperm from the testicles, combines fluids from other glands, and propels the sperm

  • Seminal vesicles – next to the ampulla of the vas deferens; secretes a nutritional bath for traveling sperm; 60-70% of the ejaculate volume; joins the vas deferens to form the ejaculatory duct that passes into the prostate and then forms the urethra

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The Ejaculatory Pathway

  • Prostate gland – walnut-sized gland beneath the bladder; secretes a fluid that neutralizes the acidity of the vagina that would be lethal to sperm; 25-30% of the ejaculate’s volume

  • Cowper’s (bulbourethral) glands – 2 pea-sized glands next to the urethra, under the prostate; contributes fluid that cleans the urethra of lethal acidic urine; comprises the majority of the pre-ejaculatory fluid

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  • Once the threshold is reached:

    • Epididymis, seminal vesicles, and prostate empty their fluids into the urethral bulb

    • A sphincter closes off the bladder

    • 5-15 contractions at the base of the penis squeeze the urethral bulb

    • Ejaculate is expelled

    • Orgasm

    • Return to flaccid state

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  • 2-5 milliliters of fluid

  • 50-150 million sperm per milliliter

  • Few sperm reach the ovum

  • Sperm work together in order to fertilize the egg

  • Semen coagulates upon ejaculation; this helps it remain in the vagina and travel into the uterus

  • 5-20 minutes later it thins out

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Other Sex Organs

  • Breasts – mostly muscle and no functional purpose; some men are sexually pleased when the nipples are stimulated

  • Erogenous zones – scrotum, testicles, anus

  • Stimulation perceived as sexually exciting can determine what is erogenous to each person

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Male Puberty


The Male Maturation Cycle

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Class Discussion

  • Do you think most men are concerned with the size of their penis? Why or why not?

  • Do you think there is a correlation between penis size and masculinity?

  • If penis enlargement surgery was 100% effective, what percentage of men do you think would have the surgery?

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Male Puberty

  • Around 10 years of age, the hypothalamus starts to release gonadotropin releasing hormone (GnRH) which signals the pituitary to release FSH and LH

  • At the testes, LH stimulates testosterone production; the two combined and FSH stimulate sperm production (around 12 years)

  • Negative feedback loop

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Male Puberty

  • Many organs and glands increase in size: testicles, penis, epididymis, prostate, seminal vesicles, Cowper’s glands

  • Growth spurt initiated by testosterone levels

  • Testosterone and DHT develop the secondary sex characteristics: larger muscles and bones, pubic hair, thick and tough skin, deep voice, facial and chest hair, increased sex drive

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  • Testosterone levels decrease about 1% per year after 40 years of age

  • In the 70s and 80s, andropause occurs

  • Andropause symptoms: decreased spermatogenesis, thinner ejaculate, less ejaculatory force, libido decreases, fatigue, mood disturbances, decreased strength

  • Controversy over hormone treatments

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Diseases of the male reproductive organs

Other conditions that affect the male reproductive organs

Cancer of the male reproductive organs

Male Reproductive and Sexual Health

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Diseases of the Male Reproductive Organs: Cryptorchidism

  • Testes do not descend into the scrotum

  • Surgery necessary to correct

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Although the testicles of a fetus begin high in the abdomen, they must descend into the scrotum during fetal development. If they do not, the male may become infertile.

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Diseases of the Male Reproductive Organs: Testicular torsion they must descend into the scrotum during fetal development. If they do not, the male may become infertile.

  • testis is twisted on its spermatic cord;

  • many causes (sex, exercise, sleep);

  • symptoms are pain and swelling;

  • immediate surgery is required to maintain the testicle

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Testicular torsion can occur after exercise, sexual intercourse, and even while sleeping.

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Diseases of the Male Reproductive Organs: Priapism intercourse, and even while sleeping.

  • persistent, painful erection not related to sexual excitement;

  • blood is trapped in erectile tissue;

  • common causes are drug use and unknown;

  • treatment is cessation of drug use and, possibly, surgery

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Diseases of the Male Reproductive Organs: Peyronie’s Disease

  • painful curvature of the penis making penetration impossible;

  • cause is unknown;

  • may disappear within 2 years, or require drugs or surgery

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Other Conditions that Affect the Male Reproductive Organs Disease

  • Anabolic-androgenic steroid use

    • synthetic testosterone can increase muscle mass and endurance;

    • there are also numerous physical, psychological, and emotional side effects, including erectile problems

  • Inguinal hernia

    • intestine goes through an abdominal opening into the scrotum, creating a bulge;

    • can be due to heavy lifting and straining;

    • surgery may be required

  • Hydrocele – fluid accrues & forms a scrotal mass

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Testicular Disease



Cancer of the Male Reproductive Organs

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Testicular Cancer Disease

  • Most common cancer in men 15-44 years

  • Few early symptoms, early detection important; testicular self-exam

  • Symptoms: painless mass or hardness in the testes; pain or increase in size of the testes, lower back pain, gynecomastia, shortness of breath, urethral obstruction

  • High cure rate: radiation, chemotherapy, removal of testicle

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Penile Cancer Disease

  • Lesions on the penis may be benign or malignant and are usually treatable; may also be a STI

  • Penile cancer is not common

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Prostate Cancer Disease

  • Prostate glands enlarge with age and this is typically unproblematic, other than interfering with urination

  • Prostate cancer is one of the most common in American men, typically in men over 50 years

  • Risk factors: age, high fat diet, race, genetics

  • Symptoms: pain in the lower back, pelvis, or upper thigh, and urinary abnormalities

  • Detected through rectal exam and blood test

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Prostate Cancer Disease

  • Treatments: “watchful waiting”, radical prostatectomy, radiation, cryosurgery, drugs that attack cancerous cells