AskDefine | Define urethra

Dictionary Definition

urethra n : duct through which urine is discharged in most mammals and which serves as the male genital duct [also: urethrae (pl)]

User Contributed Dictionary

English

Etymology

First coined 1634, from οὐρήθρα < οὐρέω.

Noun

  1. The tube through which urine exits the body and, in males, through which semen is ejaculated.

Translations

anatomical tube

Derived terms

Extensive Definition

In anatomy, the urethra (from Greek ουρήθρα - ourethra) is a tube which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes to pass urine to the outside, and also a reproductive function in the male, as a passage for semen.
The external urethral sphincter is a striated muscle that allows voluntary control over urination.

Anatomy

Female urethra

In the human female, the urethra is about 1 1/2-2 inches (3-5 cm) long and opens in the vulva between the clitoris and the vaginal opening, extending from the internal to the external urethral orifice. It is placed behind the symphysis pubis, imbedded in the anterior wall of the vagina, and its direction is obliquely downward and forward; it is slightly curved with the concavity directed forward. Its lining is composed of stratified squamous epithelium, which becomes transitional near the bladder. The urethra consists of three coats: muscular, erectile, and mucous, the muscular layer being a continuation of that of the bladder. Between the superior and inferior fascia of the urogenital diaphragm, the female urethra is surrounded by the Sphincter urethae. Somatic innervation of the external urethral sphincter is supplied by the pudendal nerve. The uro-genital sinus may be divided into three component parts. The first of these is the cranial portion which is continuous with the allantois and forms the bladder proper. The pelvic part of the sinus forms the prostatic urethra and epithelium as well as the membranous urethra and bulbo urethral glands in the male and the membranous urethra and part of the vagina in females

Male urethra

In the human male, the urethra is about 8 inches (15 cm) long and opens at the end of the penis. The inside of the urethra has a spiral groove (like rifling in a gun barrel), which makes the urine flow in a wide stream.
The urethra is divided into four parts in men, named after the location:
The length of a male's urethra, and the fact it contains a number of bends, makes catheterisation more difficult.

Histology

The epithelium of the urethra starts off as transitional cells as it exits the bladder. Further along the urethra there are stratified columnar cells, then stratified squamous cells near the external meatus (exit hole).
There are small mucus-secreting urethral glands, that help protect the epithelium from the corrosive urine.

Medical problems of the urethra

  • Hypospadias and epispadias are forms of abnormal development of the urethra in the male, where the meatus is not located at the distal end of the penis (it occurs lower than normal with hypospadias, and higher with epispadias). In a severe chordee, the urethra can develop between the penis and the scrotum.
  • Infection of the urethra is urethritis, said to be more common in females than males. Urethritis is a common cause of dysuria (pain when urinating).
  • Related to urethritis is so called urethral syndrome
  • Passage of kidney stones through the urethra can be painful and subsequently it can lead to urethral strictures.
Endoscopy of the bladder via the urethra is called cystoscopy.

Sexual physiology

The male urethra is the conduit for semen during sexual intercourse. It also serves as a passage for urine to flow.

Additional images

Image:Illu urinary system.jpg|Urinary system

External links

  • "Male Urethra"
urethra in Arabic: إحليل
urethra in Bulgarian: Пикочен канал
urethra in Catalan: Uretra
urethra in Czech: Močová trubice
urethra in German: Harnröhre
urethra in Dhivehi: ކުޑަކަމުދާ ހޮޅި
urethra in Spanish: Uretra
urethra in French: Urètre
urethra in Indonesian: Uretra
urethra in Icelandic: Þvagrás
urethra in Italian: Uretra
urethra in Hebrew: שופכה
urethra in Kurdish: Pêşborî
urethra in Latin: Urethra
urethra in Lithuanian: Šlaplė
urethra in Dutch: Urinebuis
urethra in Japanese: 尿道
urethra in Norwegian: Urinrør
urethra in Polish: Cewka moczowa
urethra in Portuguese: Uretra
urethra in Russian: Мочеиспускательный канал
urethra in Simple English: Urethra
urethra in Slovak: Močová rúra
urethra in Slovenian: Sečnica
urethra in Sundanese: Urétra
urethra in Finnish: Virtsaputki
urethra in Swedish: Urinrör
urethra in Telugu: ప్రసేకం
urethra in Chinese: 尿道
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