Male anatomy: the organs and structures of the adult male body

Whether an embryo develops male anatomy depends on a single gene on the Y chromosome, SRY. The early gonads appear about a month after conception and can become either testes or ovaries; SRY switches on the genes that build a testis, and without a working SRY gene the embryo develops as female. Soon after the testis forms, its Leydig cells start making testosterone. (OpenStax Anatomy and Physiology 2e, 27.3: Development of the Male and Female Reproductive Systems.)

Every embryo first has two duct systems. In males, testosterone makes the Wolffian duct grow into the epididymis, ductus deferens and seminal glands, while secretions from the testis make the Müllerian duct, which forms the uterus and uterine tubes in females, break down. The same tissue that becomes the glans of the penis when exposed to testosterone becomes the clitoris without it. (OpenStax Anatomy and Physiology 2e, 27.3: Development of the Male and Female Reproductive Systems.)

The 3D model above is the adult male BodyParts3D body, with the male reproductive and urinary organs and the thyroid cartilage highlighted. Lower the Skin slider to see inside, switch body systems on or off, or click any part to open its own page.

Cleveland Clinic divides the male reproductive organs into external organs (the penis, scrotum and testicles) and internal organs (the vas deferens, ejaculatory ducts, urethra, seminal vesicles, prostate and bulbourethral glands). Together they make, store and carry sperm and semen, release sperm, and produce male sex hormones. (Cleveland Clinic: Male Reproductive System.)

The testes are about 4 to 5 cm long and sit in the scrotum, where they are kept 2 to 4 °C below core body temperature for sperm production. They make about 100 to 300 million sperm a day. Sperm take on average 12 days to pass through the coiled epididymis, where they mature, and leave through the ductus deferens, which runs in the spermatic cord. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

Sperm make up only about 5% of semen. OpenStax gives the seminal glands (seminal vesicles) about 60% of semen volume, the walnut-sized prostate an alkaline fluid that helps semen clot and then liquefy, and the bulbourethral glands a thick pre-ejaculate that lubricates the urethra. OpenStax gives the average erect penis as about 15 cm. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

Cleveland Clinic gives slightly different figures: seminal vesicles make up to 80% of the fluid, and the average penis is about 8.9 cm (3.5 inches) when flaccid and a little over 13 cm (5 inches) when erect. (Cleveland Clinic: Male Reproductive System.)

Testes, ducts, glands and penis in detail, with the path of sperm and a penis cross-section. Male reproductive system.

Testosterone production is controlled by the brain. Pulses of gonadotropin-releasing hormone (GnRH) from the hypothalamus make the pituitary release luteinising hormone (LH), which stimulates Leydig cells to make testosterone, and follicle-stimulating hormone (FSH), which acts on Sertoli cells to support sperm production. Leydig cells make about 6 to 7 mg of testosterone a day, and its concentration in the testes is about 100 times that in the blood. Sertoli cells also release inhibin, which reduces FSH release, and testosterone and inhibin together feed back to damp down GnRH, LH and FSH. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

In boys, LH becomes detectable at about 8 or 9 years, mainly during sleep. The first physical sign of puberty is usually growth of the testes, followed by growth and darkening of the scrotum, growth of the penis, hair in the armpits, pubic area, chest and face, and growth of the larynx with thickening of the vocal folds, which lowers the voice. The growth spurt comes at about 11 to 13 years, first fertile ejaculations at about 15, and development can continue into the early 20s. (OpenStax Anatomy and Physiology 2e, 27.3: Development of the Male and Female Reproductive Systems.)

Cleveland Clinic lists the roles of testosterone in the adult as maintaining muscle mass and strength, fat distribution, bone mass and sex drive, and notes that sperm production may continue into a man's 80s or longer. (Cleveland Clinic: Male Reproductive System.)

The male urethra is about 15 to 20 cm long, against about 4 cm in females, and carries both urine and semen. It has a prostatic part, the widest, which receives the ejaculatory and prostatic ducts; a membranous part, the narrowest, surrounded by the external urethral sphincter; and a spongy (penile) part through the bulb and corpus spongiosum, which widens in the glans. Some authors add a short part in the bladder neck. Because of two bends, catheterising the male urethra is more complex, while the short female urethra makes women more prone to urinary tract infections. (TeachMeAnatomy: The Urethra.)

At the bladder neck, males have an internal urethral sphincter of circular smooth muscle under autonomic control, thought to stop semen flowing back into the bladder during ejaculation; females have no distinct internal sphincter. The voluntary external sphincter is more complex in males, linked with fibres of levator ani. In males, enlargement of the prostate (benign prostatic hyperplasia) is the most common cause of a blocked bladder outflow. (TeachMeAnatomy: The Bladder.)

Kenhub places the male external urethral sphincter (rhabdosphincter) just below the prostate. During orgasm, sympathetic nerves from the T11 to L2 segments of the spinal cord contract the internal sphincter, which stops semen travelling back into the bladder. (Kenhub: Urethral sphincters.)

In males the bladder lies behind the pubic symphysis with the rectovesical pouch and rectum behind it and the prostate below; in females the vesicouterine pouch, uterus, cervix and vagina lie behind it. Radiopaedia gives the normal functional volume of the adult bladder as 300 to 400 mL, whereas TeachMeAnatomy gives a storage capacity of up to 400 to 600 mL. (Radiopaedia: Urinary bladder.)

The rectovesical pouch is the lowest part of the peritoneal cavity in males. The male peritoneal cavity is completely closed, whereas in females the uterine tubes open into it. (TeachMeAnatomy: The Peritoneal Cavity.)

The bladder in 3D, with its position, capacity and sphincters. Urinary bladder.

The male pelvis is built for a heavier body and stronger muscles rather than for childbirth. Its bones are thicker and heavier, the pelvic inlet is heart-shaped, the subpubic angle under the pubic symphysis is less than 70 degrees, the pelvic outlet is smaller, and the greater sciatic notch is narrower and deeper. The female pelvis has lighter bones, a round or oval inlet, a subpubic angle greater than 80 degrees and a larger, rounder outlet. (OpenStax Anatomy and Physiology 2e, 8.3: The Pelvic Girdle and Pelvis.)

TeachMeAnatomy calls the typical male pelvis android and the typical female pelvis gynaecoid, and describes the female pelvis as wider and broader but lighter, adapted for childbirth. (TeachMeAnatomy: The Pelvic Girdle.)

Ilium, ischium and pubis in 3D, with a male vs female pelvis diagram. Pelvis bones.

The thyroid cartilage is the largest cartilage of the larynx (voice box). Its front forms the laryngeal prominence, or Adam's apple, which tends to be more prominent in males. Male vocal folds tend to be larger than female ones, which gives a deeper voice. (OpenStax Anatomy and Physiology 2e, 22.1: Organs and Structures of the Respiratory System.)

Everyone has a thyroid cartilage, and it grows at puberty, typically more in males, but the size of the Adam's apple varies from person to person. Cleveland Clinic notes that it may help protect the voice box, that whether a larger Adam's apple deepens the voice is not proven, and that having a large or small one has no effect on health. (Cleveland Clinic: Adam's Apple.)

The cartilages of the voice box and the vocal folds, labelled. Larynx.

A 2023 review of sex differences found that males become notably stronger than females at about 15 years of age and that the difference is larger in upper-body muscles than in lower-body muscles. The extra strength is explained by greater muscle mass and larger type II (fast) muscle fibres, not by the nervous system activating the muscles more fully. (Nuzzo JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res. 2023.)

Testosterone underlies these changes: circulating testosterone supports muscle development and bone growth as well as the secondary sex characteristics. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

OpenStax lists increased muscular development among the male secondary sex characteristics of puberty, alongside a larger larynx with a deeper voice and more facial, axillary, pubic and body hair. (OpenStax Anatomy and Physiology 2e, 27.3: Development of the Male and Female Reproductive Systems.)

The major muscles of the body in 3D. Muscular system.

Gynaecomastia is a benign, usually reversible excess of breast glandular tissue in males, centred under the nipple and often one-sided or uneven. Without symptoms it is found in 60 to 90% of newborn boys, 50 to 60% of adolescents and up to 70% of men aged 50 to 69. It is not in itself a risk factor for male breast cancer, and breast enlargement caused by fat alone is called pseudogynaecomastia. (Radiopaedia: Gynaecomastia.)

The ribs, chest muscles and organs of the thorax. Chest anatomy.

Males have the same pelvic floor muscles as females, but the pelvic floor has two openings in males (the urethra and anal canal) instead of three. The medial fibres of pubococcygeus that surround the prostate are called puboprostaticus. (Kenhub: Muscles of the pelvic floor.)

In males the pelvic floor holds the prostate in place and helps with erection and ejaculation as well as bladder and bowel control; prostate surgery can weaken previously strong muscles. (Cleveland Clinic: Pelvic Floor Muscles.)

The male external urethral sphincter is omega-shaped and lies between the two slings of levator ani, joined to them by fascia rich in elastic fibres, unlike the semicircular female sphincter. (Hinata N, Murakami G. The urethral rhabdosphincter, levator ani muscle, and perineal membrane: a review. Biomed Res Int. 2014.)

On the surface, the male perineum is the area between the scrotum and the anus, about 2 inches (about 5 cm) long or more. (Cleveland Clinic: Perineum.)

Levator ani, the perineal muscles and the male and female perineum, with labelled diagrams. Pelvic floor and perineum.

The testes form on the back wall of the abdomen and descend through the inguinal canal into the scrotum, guided by the gubernaculum, so in males the canal carries the spermatic cord. A pouch of peritoneum that descends with the testis, the processus vaginalis, normally closes; if it stays open it can cause an indirect inguinal hernia or a hydrocele. (TeachMeAnatomy: The Inguinal Canal.)

Both inguinal rings are larger in males, to let the testis through. (Kenhub: Inguinal canal.)

The lifetime risk of a groin hernia is 27 to 43% in men and 3 to 6% in women, and inguinal hernia repair is 8 to 10 times more common in males. Hernias peak at about 5 years of age, mainly indirect, and again at 70 to 80 years, mainly direct. (HerniaSurge Group. International guidelines for groin hernia management. Hernia. 2018.)

The inguinal ligament, inguinal canal, femoral triangle and hernia sites. Groin anatomy.

Male and female reproductive organs develop from shared starting tissue. The early gonad becomes a testis or an ovary, and the same tissue forms the glans of the penis or the clitoris, depending on whether SRY and testosterone are present. (OpenStax Anatomy and Physiology 2e, 27.3: Development of the Male and Female Reproductive Systems.)

Some smaller structures are also matched. The paraurethral (Skene) glands beside the female urethra are considered homologous to the male prostate. (TeachMeAnatomy: The Urethra.)

The table below brings together the differences covered on this page, with the source for each in the caption.

The female body: reproductive organs, pelvis, breast and pelvic floor. Female anatomy.

Cleveland Clinic lists the common conditions of the male reproductive system as testicular, penile and prostate cancer, sexually transmitted infections, premature ejaculation, male infertility, erectile dysfunction and priapism. (Cleveland Clinic: Male Reproductive System.)

Because the urethra runs through the prostate, an enlarged prostate can narrow it and restrict the flow of urine. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

In males, prostate enlargement (benign prostatic hyperplasia) is the most common obstructive cause of urinary retention, and the bladder's detrusor muscle thickens, with prominent ridges called trabeculae, as it works against the blockage. (TeachMeAnatomy: The Bladder.)

Groin hernias are another condition shaped by male anatomy: indirect inguinal hernias follow the path the testis took through the inguinal canal. This overview is educational and not a guide to diagnosis. (TeachMeAnatomy: The Inguinal Canal.)

Corpus cavernosum of penis

The corpora cavernosa are the paired columns of erectile tissue forming the dorsal part of the penis.

Corpus spongiosum of penis

The corpus spongiosum is the single column of erectile tissue surrounding the penile urethra.

Deferent duct

The deferent duct (vas deferens) is a thick-walled muscular tube carrying sperm from the epididymis toward the urethra.

Epididymis

The epididymis is a coiled tube on the posterior testis where sperm mature and are stored.

Glans penis

The glans penis is the cone-shaped distal end of the penis.

Kidney

The kidney is a bean-shaped organ that filters blood to form urine and regulate fluid, electrolytes and blood pressure.

Prostate

The prostate is a walnut-sized gland surrounding the first part of the male urethra.

Seminal vesicle

The seminal vesicles are paired glands that produce much of the fluid of semen.

Testicular artery

A paired branch of the abdominal aorta to the testis.

Testicular vein

A vein draining the testis.

Testis

The testis is the male gonad that produces sperm and testosterone.

Thyroid cartilage

The thyroid cartilage is the largest cartilage of the larynx, forming the laryngeal prominence.

Ureter

The ureter is a muscular tube carrying urine from the renal pelvis to the urinary bladder.

Urethra

The urethra is the tube carrying urine out of the bladder; in males it also carries semen.

Urinary bladder

The urinary bladder is a hollow muscular organ that stores urine.