Chapter 5: Male Sexual Anatomy and Physiology

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Chapter 5 Male Sexual Anatomy and Physiology
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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

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The Male Sexual and Reproductive System

• External Sex Organs
• Internal Sex Organs
• Other Sex Organs

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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

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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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Erection

• 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 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)

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Internal Sex Organs

• Testes
• Epididymis
• Vas deferens
• Seminal vesicles
• Prostate gland
• Cowpers glands

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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

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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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Spermatogenesis

• 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

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• Internal structure of the testicle.

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

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Spermatogenesis

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

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Spermatogenesis

• 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

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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
• Cowpers glands

All contribute something to the process
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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 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

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Ejaculation

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

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Ejaculation

• 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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Ejaculate/Semen

• 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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The Male Maturation Cycle

• Male puberty
• Andropause

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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, 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

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Andropause

• 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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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

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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 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 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

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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

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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

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Cancer of the Male Reproductive Organs

• Testicular
• Penile
• Prostate

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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

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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

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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

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Prostate Cancer

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