21.6: Urethra

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Page ID: 53835

Rosanna Hartline
West Hills College Lemoore

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Urethra

The urethra carries urine from the internal urethral orifice (opening of the urethra from the bladder) to the external urethral orifice to exit the body. There are basic differences in the lengths of the urethra between males and females with males having a longer urethra since it passes through the penis. Another difference between males and females is the types of fluid passing through the urethra. In females, the urethra is designed for urine transport only. In males however, the urethra carries urine and is also linked in with reproductive structures to carry semen (fluid containing sperm) outside of the body upon ejaculation.

$Microscopic images of male and female urethras$

Above: Cross sections of the male and female urethra, shown at two different magnifications. Male magnified by 40x and female magnified by 200x. (Left) Cross section of the penile urethra. The urethra is a fibromuscular tube that conveys urine from the bladder to the external urethra orifice. In males, the urethra is about 20 cm long and begins with the prostatic region at the neck of the bladder. Subsequent subdivisions are a short membranous urethra, which leads into the long penile (spongy) urethra. The penile urethra travels in the corpus spongiosum on the ventral side of the penis. (Right) Cross section of the female urethra. The female urethra is much shorter than in males (3-5 cm in length), and its mucosa is thrown into longitudinal folds. The transitional epithelium present as the urethra exits the bladder transitions to stratified squamous, such as seen here. The lamina propria contains a venous plexus similar to the male corpus spongiosum. In addition to two layers of smooth muscle (inner longitudinal and outer circular), an outermost layer of circular, skeletal muscle is present at the distal end.

Attributions

"Renal Anatomy" by Dongho Kim is licensed under CC BY-NC-SA 4.0
"Digital Histology" by Department of Anatomy and Neurobiology and the Office of Faculty Affairs, Virginia Commonwealth University School of Medicine and the ALT Lab at Virginia Commonwealth University is licensed under CC BY 4.0