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Chapter 5: Male Sexual Anatomy and Physiology


Erection also occurs during REM, possibly to keep the penis supplied with blood ... Priapism persistent, painful erection not related to sexual excitement; blood ... – PowerPoint PPT presentation

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Title: Chapter 5: Male Sexual Anatomy and Physiology

Chapter 5 Male Sexual Anatomy and Physiology
Food for Thought
  • All penises come in a variety of shapes and sizes
  • Important to engage in genital self-examination
    for a variety of reasons

The Male Sexual and Reproductive System
  • External Sex Organs
  • Internal Sex Organs
  • Other Sex Organs

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

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)

The Glans Penis
  • The conelike end of the penis
  • Corona
  • Frenulum
  • Meatus
  • Sensitive to stimulation

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

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

  • 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

The Scrotum
  • Loose, wrinkled pouch beneath the penis
    containing the testicles
  • Lightly covered with pubic hair
  • Functions to keep the testicles 3C cooler than
    the bodys temperature to keep sperm viable
  • Contains sweat glands
  • Cremaster muscle moves the scrotum closer to or
    farther from the body (protects)

Internal Sex Organs
  • Testes
  • Epididymis
  • Vas deferens
  • Seminal vesicles
  • Prostate gland
  • Cowpers glands

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
  • 2 primary functions
  • Testosterone production
  • Spermatogenesis

Testosterone Production
  • Testosterone is the most important male hormone
  • Interstitial, or Leydig, cells in the testicles
    produce testosterone out of cholesterol

  • Seminiferous tubules produce and store sperm
  • Sertoli cells (in the tubules) provide nutrition
    for the development of sperm
  • This process begins with spermatogonium on the
    outer wall of the tubules they move toward the
    center during development as primary
    spermatocytes, then divide to form secondary
    spermatocytes, and divide again into spermatids

  • Internal structure of the testicle.

  • Colored scan of seminiferous tubules, each
    containing a swirl of forming sperm cells (in

  • Spermatids form the compact head covered by an
    acrosome that contains enzymes to penetrate the
  • The midpiece is formed and serves as the energy
  • The flagellum propels the mature sperm
  • Sperm production takes 72 days, but is constant
    and each male produces about 300 million sperm a

  • Immature sperm travel from the tubules to the
    epididymis organ that rests atop the testicle
  • Old and faulty sperm are reabsorbed here
  • They mature in 10-14 days in the epididymis
  • Upon maturity they are transferred to the vas
    deferens for storage

The Ejaculatory Pathway
  • Ejaculation physiological process where seminal
    fluid is powerfully expelled from the penis
  • Pathway organs
  • Vas deferens
  • Seminal vesicles
  • Prostate gland
  • Cowpers glands

All contribute something to the process
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

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 ejaculates volume
  • Cowpers (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

  • Begins in the spinal cord once a threshold is
    reached, and proceeds until the conclusion

  • 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

  • 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

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

The Male Maturation Cycle
  • Male puberty
  • Andropause

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

Male Puberty
  • Many organs and glands increase in size
    testicles, penis, epididymis, prostate, seminal
    vesicles, Cowpers 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

  • 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
  • Controversy over hormone treatments

Male Reproductive and Sexual Health
  • Diseases of the male reproductive organs
  • Other conditions that affect the male
    reproductive organs
  • Cancer of the male reproductive organs

Diseases of the Male Reproductive Organs
  • Cryptorchidism testes do not descend into the
    scrotum surgery necessary to correct

  • 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.

Diseases of the Male Reproductive Organs
  • Testicular torsion 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

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

Diseases of the Male Reproductive Organs
  • Priapism 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
  • Peyronies disease painful curvature of the
    penis making penetration impossible cause is
    unknown may disappear within 2 years, or require
    drugs or surgery

Other Conditions that Affect the Male
Reproductive Organs
  • 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

Other Conditions that Affect the Male
Reproductive Organs
  • 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

Cancer of the Male Reproductive Organs
  • Testicular
  • Penile
  • Prostate

Testicular Cancer
  • 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

Penile Cancer
  • Lesions on the penis may be benign or malignant
    and are usually treatable may also be a STI
  • Penile cancer is not common

Prostate Cancer
  • 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

Prostate Cancer
  • Treatments watchful waiting, radical
    prostatectomy, radiation, cryosurgery, drugs that
    attack cancerous cells
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