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