plasbuis

Plasbuis is the Dutch term for the urethra, the tube that carries urine from the bladder to the outside of the body. In males it also conveys semen during ejaculation. The plasbuis forms part of the lower urinary tract and operates in coordination with the bladder and external sphincters to control urination.

In humans, urethral length differs by sex. The female plasbuis is about 4 cm long and opens just in front of the vagina; the male plasbuis is about 18 to 20 cm and passes through the prostate, the pelvic floor, and the length of the penis. It is divided into segments in the male: prostatic urethra, membranous urethra, and penile (spongy) urethra. The lining is mucous membrane, typically urothelium near the bladder and transitional epithelium, with changes toward stratified squamous epithelium near the external opening. The urethra also contains glands and ducts that help lubricate the opening.

Its function is to transport urine during urination, aided by internal and external urethral sphincters. In males, the urethra also serves as a conduit for semen during ejaculation, interacting with the reproductive tract.

Embryologically the plasbuis develops from the urogenital sinus with sex-specific differentiation under hormonal influence. Clinically important issues include urethritis (inflammation, commonly caused by infection), urethral strictures (narrowing that can obstruct flow), and injuries from catheterization or trauma. Congenital conditions such as hypospadias involve abnormal opening positions in males. Diagnosis relies on history, physical exam, urinalysis, and imaging such as urethrography or cystoscopy.

See also: urinary system, bladder, prostate, pelvic floor.