The urethra (from Greek οὐρήθρα – ourḗthrā) is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra connects to the urinary meatus above the vagina, whereas in marsupials, the females urethra empties into the urogenital sinus.Females use their urethra only for urinating, but males use their urethra for both urination and ejaculation. The external urethral sphincter is a striated muscle that allows voluntary control over urination. 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. The internal sphincter is present both in males and females. Structure
The urethra is a fibrous and muscular tube which connects the urinary bladder to the external urethral meatus. Its length differs between the sexes, because it passes through the penis in males. Male
In the human male, the urethra is on average 18 to 20 centimeters (7.1 to 7.9 inches) long and opens at the end of the external urethral meatus.The urethra is divided into four parts in men, named after the location:
There is inadequate data for the typical length of the male urethra; however, a study of 109 men showed an average length of 22.3 cm (SD = 2.4 cm), ranging from 15 cm to 29 cm.
Catheterisation
A tube called a catheter can be inserted through the urethra to drain urine from the bladder, called an indwelling urinary catheter; or, to bypass the urethra, a catheter may be directly inserted through the abdominal wall into the bladder, called a suprapubic catheter. This may be to relieve or bypass an obstruction, to monitor how much urine someone produces, or because a person has difficulty urinating, for example due to a neurological cause such as multiple sclerosis. Complications that are associated with catheter insertion can include catheter-associated infections, injury to the urethra or nearby structures, or pain. Other animals
History
The word "urethra" comes from the Ancient Greek stem "uro" relating to urination, with the structure described as early as the time of Hippocrates. 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. 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. Following this, in the 19th and 20th centuries multiple terms relating to the structures such as urethritis and urethrography, were coined.Kidney stones have been identified and recorded about as long as written historical records exist. The urinary tract as well as its function to drain urine from the kidneys, has been described by Galen in the second century AD.