Chapter 4
MALE SEXUAL ANATOMY
AND PHYSIOLOGY
Learning Objectives
External Sex Organs
 Internal Sex Organs
 Health Problems of the Urogenital System
 Male Sex Functions

External Sex Organs
The Penis
• Male sex organ used in sexual intercourse
• Serves as conduit for urine and sperm
• Contains cylinders of spongy material
External Sex Organs
Penis Glans
Highly sensitive tip of the penis
Corona
Ridge that separates the glans
from the body of the penis
Frenulum
Sensitive strip of tissue that connects the
underside of the penile glans to the shaft
Root
Base of the penis that extends into the pelvis
Shaft
Body of the penis that expands as a
result of vasocongestion
Foreskin
Loose skin that covers the penile glans
(prepuce)
External Sex Organs
Circumcision
• Surgical removal of the
foreskin
• Has religious roots
• Performed for health
reasons
• Painful but not
remembered
• May lessen sexual
sensations
Critical Thinking
• What are the
similarities and
differences between
male circumcision and
female circumcision
(clitoridectomy). Can
one logically favor
one of these
practices over the
other?
External Sex Organs
Penis
Size
• Cultural measure
of masculinity and
prowess
• Range in size
• Flaccid – 3 to 4
inches
• Erect – 5 to 7
inches
External Sex Organs
Penis
Size
• Surveys indicated
most woman (85%)
are satisfied with
the size of their
partner’s penis
• 55% of men are
not satisfied with
the size of their
penis
External Sex Organs
Scrotum
• Pouch of
loose skin
located
below the
penis
• Contains the
testes
Spermatic
Cord
• Suspends testicle
within the scrotum
• Contains vas
deferens, blood
vessels, nerves,
cremaster muscle
• Raise and lower
testes in response to
temperature
changes
Dartos Muscle
• Contracts and
relaxes in
response to
temperature
changes
• Increase or
decreases
surface area
of the scrotum
Internal Sex Organs
Testes
Males sex glands (gonads), suspended in
the scrotum
Produce sperm cells and male sex
hormones
Internal Sex Organs
Testosterone
Male steroid sex hormone
Secreted by interstitial cells
Stimulates
Prenatal differentiation of male
sex organs
Development of secondary sex
characteristics
Production regulated by
pituitary hormones
LH stimulates secretion of
testosterone
FSH regulates sperm production
Internal Sex Organs
Sperm
Seminiferous tubules
Tiny, winding, spermproducing tubes within the
lobes of the testes
Spermatogenisis
Process by which sperm cells are
produced and developed
Spermatozoa are mature sperm
cells
Epididymis
Tube that lies against the back
wall of each testicle and stores
sperm
Internal Sex Organs
Vas
Deferens
Tube that conducts sperm from the testicle to the
ejaculatory duct of the penis
Vasectomy
Sterilization procedure in which the
vas deferens is severed
Prevents sperm from reaching the
ejaculatory duct
Removes sperm but not fluids from the
ejaculate
Internal Sex Organs
Seminal
Vesicles
Two small glands that lie behind the bladder and
secrete fluids that combine with sperm in the
ejaculatory duct
The fluids produced are rich in nutrients to help
ensure sperm motility
Internal Sex Organs
Prostrate
Gland
Lies beneath the bladder and secretes fluid
that gives semen its characteristic odor and
texture
Prostrate fluid is
alkaline
Neutralizes some acidity in
vaginal tract
Prolongs life of sperm
Internal Sex Organs
Cowper’s
Gland
Lies below the prostrate
Secretes clear, slippery fluid into the
urethra during sexual arousal
Secretion may reduce male
acidity and also lubricate
passageway for sperm
Not enough produced to
lubricate the vagina during
intercourse
Also known as the bulbourethral glands
Internal Sex Organs
Semen
Whitish fluid that constitutes the ejaculate
Consists of sperm and the
fluids secreted by the
seminal vesicles, the
prostate gland, and the
Cowper’s glands
70% from seminal vesicle
30% sperm and other fluids
Sperm only 1%, 200-400
million sperm
Health Problems of the Urogenital System
Urethritis
• Bladder and urethral inflammations
• Strong need to urinate
• Burning sensation
• Frequent urination
• Penile discharge
• Prevention
• Drink more water, cranberry juice
• Lower intake of alcohol and caffeine
Health Problems of the Urogenital System
Cancer of the Testes
• Relatively rare
• About 8,000 cases per year, 350 deaths
• Most common form of solid-tumor cancer for men
20-34
• No evidence cancer results form sexual overactivity or masturbation
• Favorable prognosis if detected early
• Five year survival rate 99% if detected before
spreading
Health Problems of the Urogenital System
Self-examination is
best performed
shortly after a warm
shower or bath, when
the skin of the
scrotum is most
relaxed.
Roll each testicle
gently between the
thumb and fingers.
Lumps are generally
found on the front or
side of the testicle.
Self Examination of the Testes
Lump on testicle
Enlargement or swelling
Change in consistency
Dull ache in lower abdomen or groin
Health Problems of the Urogenital System
Benign Prostatic Hyperplasia (BPH)
• Non-cancerous enlargement of the prostrate due
to hormonal changes associated with aging
• Symptoms include
• Frequent and urgent urination
• Difficulty starting and stopping flow
Health Problems of the Urogenital System
Prostatitis
• Inflammation of the prostate
• Symptoms include
• Ache or pain between scrotum and anal
opening
• Painful ejaculation
Health Problems of the Urogenital System
Cancer of the Prostate
• Second most common form of cancer among men
• Second leading cause of cancer deaths in men
• Risk factors include age, family history, gene mutations,
and race
• Symptoms include problems with erection, urinary
frequency and urgency, blood in urine, pain or burning
when urinating, pain in lower back or extremities, loss of
bladder or bowel control
• Early diagnosis can provide treatment before spreading
• Not necessarily lethal
Male Sexual Functions
Erection
Engorgement of the penis
with blood causing it to
stiffen and widen
Reverses when blood
begins to flow out
Affected by psychological
factors
Possible throughout the
lifetime
Performance anxiety
- Feelings of dread connected
with an activity
Male Sexual Functions
Spinal
Reflexes
& Sexual
Response
Sexual reflexes are
automatic, unlearned
responses to sexual
stimulation
Need not try to be aroused
Spinal reflexes do not
require direct participation
of the brain, but brain can
trigger a spinal reflex
Erection and ejaculation
Erection center is located in
the sacrum
Erection is possible even with
spinal injury
Male Sexual Functions
Role of
the
Brain
Regulates sexual responses
Sends impulses to the
erection center in the upper
back
Relay center between brain and
penis that allows perceptual,
cognitive, and emotional
responses to contribute to
erection
If connection is inoperable, men
fail to achieve erection solely by
mental stimulation
Men require more sexual excitation to achieve full erection
as they age
Brain can also stifle a sexual response
Male Sexual Functions
Role of the Division of the nervous system that regulates
autonomic automatic bodily responses, such as erection
nervous
Branch of ANS most active
Sympathetic
system
during emotional responses that
(ANS)
spend the body’s energy
Largely controls ejaculation
Parasympathetic
Branch of ANS most active
during processes that restore the
body’s energy
Largely controls erection
Male Sexual Functions
Erectile
Abnormalities
Pyronie’s Disease
Excessive curvature that makes
erections painful
Priapism
Erections that persist for hours
Causes include leukemia, sickle
cell disease, diseases of the
spinal cord
Dangerous due to lack of
oxygen to penile tissue
Male Sexual Function
Critical Thinking
Since erection and
ejaculation are
reflexes, how is it that
people can consciously
cause them to happen?
Male Sexual Functions
Ejaculation
Orgasm
Spinal Reflex
• Peak of sexual excitement
• Release of tension
• One can ejaculate without
orgasm
Male Sexual Functions
Ejaculation
Emission phase
• Involves contractions of prostate, seminal
vesicles, and upper part of vas deferens
• Fluid is propelled into the urethral tract
Expulsion Phase
• Muscles at base of penis and
elsewhere contract, forcing out
semen and providing pleasure
Male Sexual Functions
Retrograde Ejaculation
• Ejaculate empties into the bladder
• Sphincter actions are reversed
• Results in dry orgasm
• Can result in infertility, but otherwise
harmless