Male Sexual Anatomy and Physiology Chapter 4 This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program. Copyright 2008 Allyn & Bacon

Male Sexual Anatomy and Physiology External Sex Organs Internal Sex Organs Diseases of the Urogenital System Male Sexual Functions Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs The Penis Male organ of sexual intercourse Serves as a conduit for urine and sperm Contains cylinders of spongy material Corpora cavernosa Spongy tissues that become congested with blood and stiffen during sexual arousal Corpus spongiosum Spongy body that runs along the bottom of the penis Contains the penile urethra Enlarges at the tip of the penis to form the glans Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs 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 Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs Root Base of the penis, which extends into the pelvis Shaft Body of the penis, which expands as a result of vasocongestion Foreskin (or prepuce) Loose skin that covers the penile glans Circumcision Surgical removal of the foreskin of the penis Has religious roots Becoming less common in the US, as it is no longer considered medically necessary Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs Penis size Considered a measure of a man’s masculinity Clinicians report that women in dysfunctional relationships are less likely to complain about the size of their partners’ penises than they are about their partners’ ability to communicate. The average erect penis ranges from 5 to 7 inches in length. Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon External Sex Organs The Scrotum Pouch of loose skin that contains the testes Located beneath the penis Spermatic cord Suspends a testicle within the scrotum and contains vas deferens, blood vessels, nerves, and the cremaster muscle Cremaster muscle: raises and lowers testes in response to temperature change Dartos muscle Like the cremaster muscle, contracts and relaxes in response to temperature changes Increases and decreases the surface area of the scrotum Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs The Testes Male sex glands, suspended in the scrotum Produce sperm cells (male germ cells) and male sex hormones (androgens) Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Testosterone Male steroid sex hormone Interstitial cells Cells that secrete testosterone Also known as Leydig’s cells Responsible for prenatal differentiation of male sex organs Stimulates the development of secondary sex characteristics Traits that distinguish the genders but are not directly involved in reproduction Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Regulated by pituitary hormones LH stimulates the secretion of testosterone FSH regulates the production of sperm Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Sperm Seminiferous tubules Tiny, winding, sperm-producing tubes located within the lobes of the testes Spermatogenesis Process by which sperm cells are produced and developed Spermatocyte Early stage in the development of sperm cells Spermatids are cells formed by the division of spermatocytes; each spermatid has 23 chromosomes. Spermatozoa are mature sperm cells. Epididymis: Tube that lies against the back wall of each testicle and stores sperm Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Passage of Spermatozoa Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs The 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 ejaculate Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs The Seminal Vesicles Small glands that lie behind the bladder and secrete fluids that combine with sperm in the ejaculatory duct A duct formed by the convergence of a vas deferens with a seminal vesicle The fluids produced are rich in nutrients to help ensure sperm motility. Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs The Prostate Gland Lies beneath the bladder and secretes prostatic fluid, which gives semen its characteristic odor and texture Alkaline in fluid neutralizes some of the vaginal acidity, which prolongs sperm life Cowper’s Glands Lie below the prostate and empty their secretions into the urethra during sexual arousal Secretion may reduce male acidity and also lubricate passageway for sperm Also known as the bulbourethral glands Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Internal Sex Organs Semen Whitish fluid that constitutes the ejaculate, consisting of sperm and the fluids secreted by the seminal vesicles, the prostate gland, and the Cowper’s glands The seminal vesicles contribute about 70% of the fluid in the ejaculate. The remaining 30% consists of sperm and fluids produced by the prostate gland and the Cowper’s glands. Sperm make up only about 1% of the ejaculate, but typically it contains 200-400 million sperm. Copyright 2008 Allyn & Bacon

Diseases of the Urogenital System Urethritis Inflammation of the bladder or urethra Cancer of the Testes Cryptorchidism One of two testicles fails to descend from the abdomen into the scrotum Affects about 14% of men with testicular cancer Self-examination of the testes Warning signals are slight enlargement or change in consistency of a testicle, dull ache in the groin, and sensation of heaviness in a testicle. Very high survival rate when detected early Copyright 2008 Allyn & Bacon

Diseases of the Urogenital System Disorders of the Prostate Benign prostatic hyperplasia Enlargement of the prostate gland due to hormonal changes associated with aging Symptoms include frequent and urgent urination, and difficulty starting the flow of urine Cancer of the prostate Second most common form of cancer among men Second leading cause of cancer deaths in men Survival rate has improved to 80% Prostatitis Inflammation of the prostate gland Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Erection Engorgement with blood causes the penis to expand and stiffen Reverses when blood begins to flow out Affected by psychological factors Performance anxiety Feelings of dread and foreboding experienced in connection with an activity that might be judged by others, e.g., sexual activity Possible throughout the life span Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Spinal Reflexes and Sexual Response Reflex Simple, unlearned response to a stimulus that is mediated by the spine rather than the brain Responsible for a male’s sexual responses, erection and ejaculation, regardless of source of stimulation Role of the spinal cord Sacrum Thick, triangular bone located near the bottom of the spinal column Center that controls reflexive erections Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Role of the brain Regulates sexual responses Sends impulses to the erection center in the upper back This center is a relay center between the brain and the penis and allows perceptual, cognitive, and emotional responses to contribute to an erection. When connections between the brain and this center are inoperable, men fail to achieve erections solely in response to mental stimulation. Men require more sexual excitation to achieve full erection as they age. Brain can also stifle sexual response Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Role of the autonomic nervous system (ANS) Division of the nervous system that regulates automatic bodily responses, such as an erection Sympathetic Branch of ANS most active during emotional responses that spend the body’s energy reserves Largely controls ejaculation Parasympathetic Branch of ANS most active during processes that restore the body’s energy reserves Largely controls erection Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Erectile abnormalities Peyronie’s disease An abnormal condition characterized by an excessive curvature of the penis that can make erections painful Caused by buildup of fibrous tissue in the penile shaft Most cases require medical attention Priapism Erections that persist for hours or days Causes include leukemia, sickle cell anemia, or diseases of the spinal cord Can be dangerous due to loss of oxygen to penile tissues Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Ejaculation Orgasm Peak of sexual excitement Release of sexual tension that builds up during arousal Not synonymous with ejaculation – one can ejaculate without orgasm Emission phase First phase of ejaculation, which involves contractions of the prostate gland, seminal vesicles, and the upper part of the vas deferens (the ampulla) Fluid is propelled into the urethral teact Expulsion stage The second stage of ejaculation, during which muscles at the base of the penis and elsewhere contract, forcing out semen and providing pleasure Copyright 2008 Allyn & Bacon

Copyright 2008 Allyn & Bacon Male Sexual Functions Retrograde ejaculation Ejaculate empties into the bladder Actions of sphincters are reversed such that the internal bladder sphincter opens Results in a dry orgasm Can result in infertility, but otherwise harmless Copyright 2008 Allyn & Bacon