Male Sexual Anatomy and Physiology Chapter 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 Organs Penis Glans Corona Frenulum Root Shaft Foreskin 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 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

Penis Size External Sex Organs Cultural measure of masculinity and prowess Range in size Flaccid – 3 to 4 inches Erect – 5 to 7 inches Penis Size

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 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 Spermatogenisis Tiny, winding, sperm-producing 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 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 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 Performance anxiety - Feelings of dread connected with an activity Possible throughout the lifetime

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 autonomic nervous system (ANS) Division of the nervous system that regulates automatic bodily responses, such as erection Sympathetic Branch of ANS most active during emotional responses that 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 Pyronie’s Disease Priapism 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 Spinal Reflex Orgasm Peak of sexual excitement Release of tension One can ejaculate without orgasm Ejaculation

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

Retrograde Ejaculation 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