urethra

urethra

the canal that in most mammals conveys urine from the bladder out of the body. In human males it also conveys semen

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

urethra

[yə′rē·thrə]

(anatomy)

The canal in most mammals through which urine is discharged from the urinary bladder to the outside.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Urethra

 

the terminal section of the urinary tract in some invertebrates, in all vertebrates, and in man. The urethra is a tube whose wall consists of an internal mucous membrane, a muscular membrane, and a connective tissue membrane.

In males the urethra emerges from the urinary bladder, descends through the prostate gland, passes between the two layers of the urogenital diaphragm under the pubic arch, enters the corpus spongiosum of the penis, and opens to the exterior of the body at the tip of the penis. The male urethra is about 20 cm long and about 7 mm in diameter. In females the urethra is much shorter—about 5 cm—and follows an almost straight path that ends in an external opening in the vestibule of the vagina. The section of the urethra that emerges from the urinary bladder is surrounded by a sphincter—a ring-shaped constrictor muscle.

The walls of the empty urethra are normally touching, becoming distended only during urination. In males the orifices of the deferent ducts and of the prostate gland open into the urethra at the point where the urethra passes through the prostate; thus, both urine and semen are expelled through the male urethra. The mucous membrane of the urethra contains glands. Inflammatory processes in the urethra can result in constriction caused by scarring, a condition that requires surgical treatment.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.