Urethra
The urethra (pl.: urethras or urethrae) is the tube that connects the mammalian urinary bladder to the urinary meatus. In placental mammals, the urethra transports urine through the penis or vulva during urination and semen through the penis during ejaculation.[1]
Not to be confused with ureter.Urethra
urethra feminina (female); urethra masculina (male)
οὐρήθρα
The external urethral sphincter is a striated muscle that allows voluntary control over urination.[2] The internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the sympathetic division of the autonomic nervous system.[3] The internal sphincter is present both in males and females.[4][5][6]
Other animals[edit]
In all mammals, with the exception of monotremes, and in both sexes, the urethra serves primarily to drain and excrete urine, which in mammals, collects in the urinary bladder and is released from there into the urethra. In addition, the closing mechanisms of the urethra, together with immunoglobulins, largely prevent germs from penetrating the inside of the body.[25] In marsupials, the female's urethra empties into the urogenital sinus.[26]
History[edit]
The word "urethra" comes from the Ancient Greek οὐρήθρα – ourḗthrā. The stem "uro" relating to urination, with the structure described as early as the time of Hippocrates.[27] Confusingly however, at the time it was called "ureter". Thereafter, terms "ureter" and "urethra" were variably used to refer to each other thereafter for more than a millennia.[27] It was only in the 1550s that anatomists such as Bartolomeo Eustacchio and Jacques Dubois began to use the terms to specifically and consistently refer to what is in modern English called the ureter and the urethra.[27] Following this, in the 19th and 20th centuries, multiple terms relating to the structures such as urethritis and urethrography, were coined.[27]
Kidney stones have been identified and recorded about as long as written historical records exist.[28] The urinary tract as well as its function to drain urine from the kidneys, has been described by Galen in the second century AD.[29] Surgery to the urethra to remove kidney stones has been described since at least the first century AD by Aulus Cornelius Celsus.[29]
Position of the urethra in males
Transverse section of the penis
Male urethral opening on glans penis
Muscles of the female perineum
Urethra. Deep dissection. Serial cross section.
