Download Chapter Four - public.iastate.edu

Chapter Four
Male Sexual Anatomy and Physiology
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…”
 Do not put your name on the paper, but turn it
in.
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)
Internal structure of the penis (side view)
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
Women report greater sexual satisfaction with
partner’s who have not been circumcised
(O’Hara & O’Hara, 1999)
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.
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
The male reproductive organs.
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
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)
Internal Sex Organs
Testes
Epididymis
Vas deferens
Seminal vesicles
Prostate gland
Cowper’s glands
The male reproductive organs.
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)
Testosterone Production
 Testosterone is the most important male
hormone
 Interstitial, or Leydig, cells in the testicles
produce testosterone out of cholesterol
Spermatogenesis
 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
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
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 ejaculate’s volume
 Cowper’s (bulbourethral) glands – 2 peasized 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
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
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
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
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?
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, 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
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
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
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
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
 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