corona: The 'crown,' a ridge of flesh demarcating where the head of the penis and the shaft join.

corpora cavernosa: The corpora cavernosa are the two spongy bodies oferectile tissue on either side of the penis which become engorged with blood from arteries in the penis, thus causing erection.

cowper's glands: The Cowper's glands secrete a small amount ofpre-ejaculate fluid prior to orgasm. This fluid neutralizes the acidity within the urethra itself.

ejaculatory ducts: The path through the seminal glands which semen travels during ejaculation.

epididymis: The epididymis is a 'holding pen' where sperm produced by the seminiferous tubules mature. The sperm wait here until ejaculation or nocturnal emission. 

foreskin, prepuce: A roll of skin which covers the head of the penis in uncircumsized men.

frenulum, frenum: A thin strip of flesh on the underside of the penis that connects the shaft to the head.

glans: The glans is clearly visible in illustration (A) as the head of the penis. The glans in uncircumcised men is usually covered by the prepuce. The glans is highly sensitive, as is the corona, the ridge of flesh that connects the glans to the shaft of the penis. 

prostate gland: Also produces a fluid that makes up the semen. The prostate gland also squeezes shut the urethral duct to the bladder, thus preventing urine from mixing with the semen and disturbing the pH balance required by sperm. 

scrotum: The scrotum is a sac that hangs behind and below the penis, and contains the testes, the penis sexual glands. The scrotum's primary function is to maintain the testes at approximately 34 C, the temperature at which the testes most effectively produce sperm. 

seminal vesicles: The seminal vesicles produce semen, a fluid that activates and protects the sperm after it has left the penis during ejaculation 

smemga: A substance with the texture of cheese secreted by glands on each side of the frenulum in uncircumsized men.

testes, testicles: The penis sexual glands, the two testes within the scrotum produce sperm and testosterone. Within each testis is a kilometer of ducts called the seminiferous tubules, the organs which generate sperm. Each testicle produces nearly 150 million sperm every 24 hours. 

urethra, meatus: The opening at the tip of the penis to allow the passage of both urine and semen.

vas deferens: The ducts leading from the epididymis to the seminal vesicles. These are the ducts that are cut during the procedure known as vasectomy.