MALE SEXUAL ANATOMY AND PHYSIOLOGYChapter 4

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 OrgansPenis

Glans Highly sensitive tip of the penis

Corona Ridge that separates the glans from the body of the penisFrenulum Sensitive strip of tissue that connects the underside of the penile glans to the shaftRoot 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 OrgansCircumcision

• Surgical removal of the foreskin

• Has religious roots• Performed for health

reasons• Painful but not

remembered• May lessen sexual

sensations

• What are the similarities and differences between male circumcision and female circumcision (clitoridectomy). Can one logically favor one of these practices over the other?

Critical Thinking

External Sex Organs

• Cultural measure of masculinity and prowess

• Range in size• Flaccid – 3 to

4 inches• Erect – 5 to 7

inches

Penis Size

External Sex Organs

• 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

Penis Size

External Sex OrgansScrotum

• 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 OrgansTestes

Males sex glands (gonads), suspended in the scrotum

Produce sperm cells and male sex hormones

Internal Sex OrgansTestosterone

Male steroid sex hormone

Secreted by interstitial cellsStimulates Prenatal differentiation of

male sex organsDevelopment of secondary sex characteristics

Production regulated by pituitary hormones

LH stimulates secretion of testosteroneFSH regulates sperm production

Internal Sex Organs

Sperm

Seminiferous tubules

Tiny, winding, sperm-producing tubes within the lobes of the testes

Spermatogenisis Process by which sperm cells are produced and developedSpermatozoa are mature sperm cells

Epididymis Tube that lies against the back wall of each testicle and stores sperm

Internal Sex OrgansVas Deferens

Tube that conducts sperm from the testicle to the ejaculatory duct of the penis

Vasectomy Sterilization procedure in which the vas deferens is severedPrevents sperm from reaching the ejaculatory duct

Removes sperm but not fluids from the ejaculate

Internal Sex OrgansSeminal 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 OrgansProstrate 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 OrgansCowper’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 OrgansSemen 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

• 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

Urethritis

Health Problems of the Urogenital System

• 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

over-activity or masturbation• Favorable prognosis if detected early• Five year survival rate 99% if detected

before spreading

Cancer of the Testes

Health Problems of the Urogenital System

Self Examination of the Testes

Lump on testicle

Enlargement or swelling

Change in consistency

Dull ache in lower abdomen or groin

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.

Health Problems of the Urogenital System

• Non-cancerous enlargement of the prostrate due to hormonal changes associated with aging

• Symptoms include• Frequent and urgent urination• Difficulty starting and stopping flow

Benign Prostatic Hyperplasia (BPH)

Health Problems of the Urogenital System

• Inflammation of the prostate• Symptoms include• Ache or pain between scrotum and

anal opening• Painful ejaculation

Prostatitis

Health Problems of the Urogenital System

• 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

Cancer of the Prostate

Male Sexual FunctionsErection

Engorgement of the penis with blood causing it to stiffen and widenReverses when blood begins to flow out

Affected by psychological factors

Performance anxiety- Feelings of dread connected with an activity

Possible throughout the lifetime

Male Sexual FunctionsSpinal 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 FunctionsRole 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 erectionIf connection is inoperable, men fail to achieve erection solely by mental stimulationMen require more sexual excitation to achieve

full erection as they ageBrain can also stifle a sexual response

Male Sexual FunctionsRole of the autonomic nervous system (ANS)

Division of the nervous system that regulates automatic bodily responses, such as erectionSympathetic Branch of ANS most

active during emotional responses that spend the body’s energyLargely controls ejaculation

Parasympathetic Branch of ANS most active during processes that restore the body’s energy Largely controls erection

Male Sexual FunctionsErectile 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 cordDangerous 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

Spinal Reflex

Orgasm• Peak of sexual excitement• Release of tension• One can ejaculate without

orgasm

Ejaculation

Male Sexual Functions

Expulsion Phase• M

uscles at base of penis and elsewhere contract, forcing out semen and providing pleasure

Ejaculation

Male Sexual Functions

Retrograde EjaculationEjaculate empties into the bladder

Sphincter actions are reversedResults in dry orgasm

Can result in infertility, but otherwise harmless