The urethra (: urethras or urethrae) is the tube that connects the
urinary bladder
The bladder () is a hollow organ in humans and other vertebrates that stores urine from the Kidney (vertebrates), kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the ...
to the
urinary meatus, through which
placental mammals urinate
Urination is the release of urine from the bladder through the urethra in placental mammals, or through the cloaca in other vertebrates. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, ure ...
and
ejaculate
Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the penis through the urethra. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural concepti ...
.
The external
urethral sphincter
The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the external sphincter muscle of male urethra, male or external sphincter muscle of female urethra, fe ...
is a
striated muscle
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. Under the microscope, sarcomeres are visible along muscle fibers, giving a striated appearance to the tissue. The two types of striated muscle a ...
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 autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...
.
The internal sphincter is present both in males and females.
Structure
The urethra is a fibrous and muscular tube which connects the
urinary bladder
The bladder () is a hollow organ in humans and other vertebrates that stores urine from the Kidney (vertebrates), kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the ...
to the
external urethral meatus
The urinary meatus (, ; : meati or meatuses), also known as the external urethral orifice, is the opening of the penis or vulva where urine exits the urethra during urination. It is also where semen exits during male ejaculation, and other fluids ...
. Its length differs between the sexes, because it passes through the
penis
A penis (; : penises or penes) is a sex organ through which male and hermaphrodite animals expel semen during copulation (zoology), copulation, and through which male placental mammals and marsupials also Urination, urinate.
The term ''pen ...
in males.
Male

In the human male, the urethra is on average 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.
The urethra in male placental mammals is typically longer than in females.
Female
In the human female, the urethra is about 4 cm long,
having 6 mm diameter,
and exits the body between the
clitoris
In amniotes, the clitoris ( or ; : clitorises or clitorides) is a female sex organ. In humans, it is the vulva's most erogenous zone, erogenous area and generally the primary anatomical source of female Human sexuality, sexual pleasure. Th ...
and the
vaginal opening, extending from the
internal to the
external urethral orifice. The meatus is located below the clitoris. It is placed behind the
symphysis pubis, embedded in the anterior wall of the vagina, and its direction is obliquely downward and forward; it is slightly curved with the concavity directed forward. The proximal two-thirds of the urethra is lined by
transitional epithelial cells, while the distal third is lined by
stratified squamous epithelial cells.
Between the
superior and
inferior fascia of the
urogenital diaphragm
Older texts have asserted the existence of a urogenital diaphragm, also called the triangular ligament, which was described as a layer of the pelvis that separates the deep perineal sac from the upper pelvis, lying between the inferior fascia of ...
, the female urethra is surrounded by the
urethral sphincter
The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the external sphincter muscle of male urethra, male or external sphincter muscle of female urethra, fe ...
.
The urethra in female placental mammals is typically shorter than in the male.
Microanatomy
The cells lining the urethra (the
epithelium
Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...
) start off as
transitional cells as it exits the bladder, which are variable layers of flat to cuboidal cells that change shape depending on whether they are compressed by the contents of the urethra.
Further along the urethra there are
pseudostratified columnar and
stratified columnar epithelia.
The lining becomes
multiple layers of flat cells near the end of the urethra, which is the same as the external skin around it.
There are small
mucus
Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...
-secreting urethral glands, as well as bulbo-urethral glands of Cowper, that secrete mucous acting to lubricate the urethra.
The urethra consists of three coats: muscular, erectile, and mucous, the muscular layer being a continuation of that of the bladder.
Blood and nerve supply and lymphatics
Somatic (conscious) innervation of the
external urethral sphincter is supplied by the
pudendal nerve
The pudendal nerve is the main nerve of the perineum. It is a Mixed nerve, mixed (motor and sensory) nerve and also conveys Sympathetic nervous system, sympathetic Autonomic nervous system, autonomic fibers. It carries sensation from the exter ...
.
Development
In the developing
embryo
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
, at the hind end lies a
cloaca
A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...
. This, over the fourth to the seventh week, divides into a
urogenital sinus
The urogenital sinus is a body part of a human or other Placentalia, placental only present in the development of the urinary system, development of the urinary and development of the reproductive organs, reproductive organs. It is the ventral p ...
and the beginnings of the
anal canal
The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional s ...
, with a wall forming between these two inpouchings called the
urorectal septum.
The urogenital sinus divides into three parts, with the middle part forming the urethra; the upper part is largest and becomes the
urinary bladder
The bladder () is a hollow organ in humans and other vertebrates that stores urine from the Kidney (vertebrates), kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the ...
, and the lower part then changes depending on the biological sex of the embryo.
The cells lining the urethra (the epithelium) come from
endoderm
Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...
, whereas the connective tissue and smooth
muscle
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
parts are derived from
mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...
.
After the third month, urethra also contributes to the development of associated structures depending on the biological sex of the embryo. In the male, the epithelium multiples to form the
prostate
The prostate is an male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemica ...
. In the female, the upper part of the urethra forms the urethra and
paraurethral glands.
Function
Urination
The urethra is the vessel through which urine passes after leaving the bladder. During urination, the smooth muscle lining the urethra relaxes in concert with bladder contraction(s) to forcefully expel the urine in a pressurized stream. Following this, the urethra re-establishes muscle tone by contracting the smooth muscle layer, and the bladder returns to a relaxed, quiescent state. Urethral smooth muscle cells are mechanically coupled to each other to coordinate mechanical force and electrical signaling in an organized, unitary fashion.
Ejaculation
The male urethra is the conduit for
semen
Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoon, spermatozoa which is secreted by the male gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals. In humans and placen ...
during
orgasm
Orgasm (from Greek , ; "excitement, swelling"), sexual climax, or simply climax, is the sudden release of accumulated sexual excitement during the sexual response cycle, characterized by intense sexual pleasure resulting in rhythmic, involu ...
.
Urine is removed before ejaculation by
pre-ejaculate fluid – called Cowper's fluid – from the bulbourethral gland.
Clinical significance

Infection of the urethra is
urethritis, which often causes purulent urethral discharge.
It is most often due to a
sexually transmitted infection
A sexually transmitted infection (STI), also referred to as a sexually transmitted disease (STD) and the older term venereal disease (VD), is an infection that is Transmission (medicine), spread by Human sexual activity, sexual activity, e ...
such as
gonorrhoea or
chlamydia
Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium ''Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear, they may occur only several w ...
, and less commonly due to other bacteria such as
ureaplasma or
mycoplasma;
trichomonas vaginalis
''Trichomonas vaginalis'' is an Anaerobic organism, anaerobic, flagellated protozoan parasite and the causative agent of a Sexually transmitted infection, sexually transmitted disease called trichomoniasis. It is the most common pathogenic protoz ...
; or the viruses
herpes simplex virus
Herpes simplex virus 1 and 2 (HSV-1 and HSV-2) are two members of the Herpesviridae#Human herpesvirus types, human ''Herpesviridae'' family, a set of viruses that produce Viral disease, viral infections in the majority of humans. Both HSV-1 a ...
and
adenovirus
Adenoviruses (members of the family ''Adenoviridae'') are medium-sized (90–100 nm), nonenveloped (without an outer lipid bilayer) viruses with an icosahedral nucleocapsid containing a double-stranded DNA genome. Their name derives from t ...
.
Investigations such as a
gram stain
Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes ...
of the discharge might reveal the cause;
nucleic acid testing based on the
first urine sample passed in a day, or a swab of the urethra sent for
bacterial culture and sensitivity
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
may also be used.
Treatment usually involves
antibiotic
An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...
s that treat both gonorrhoea and chlamydia, as these often occur together.
A person being treated for urethritis should not have sex until the infection is treated, so that they do not spread the infection to others.
Because of this spread, which may occur during an
incubation period
Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or ionizing radiation, radiation, and when symptoms and signs are first apparent. In a typical infect ...
before a person gets symptoms, there is often
contact tracing
In public health, contact tracing is the process of identifying people who may have been exposed to an infected person ("contacts") and subsequent collection of further data to assess transmission. By tracing the contacts of infected individua ...
so that sexual partners of an affected person can be found and treatment offered.
Cancer can also develop in the lining of the urethra.
When cancer is present, the most common symptom in an affected person is
blood in the urine; a physical
medical examination
In a physical examination, medical examination, clinical examination, or medical checkup, a medical practitioner examines a patient for any possible medical signs or symptoms of a Disease, medical condition. It generally consists of a series of ...
may be otherwise normal, except in late disease.
Cancer of the urethra is most often due to cancer of the cells lining the urethra, called
transitional cell carcinoma, although it can more rarely occur as a
squamous cell carcinoma
Squamous-cell carcinoma (SCC), also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the ...
if the type of cells lining the urethra have changed, such as due to a chronic
schistosomiasis
Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever is a neglected tropical helminthiasis, disease caused by parasitism, parasitic Schistosoma, flatworms called schistosomes. It affects both humans and animals. It affects ...
infection.
Investigations performed usually include collecting a sample of urine for an inspection for malignant cells under a microscope, called
cytology
Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living an ...
, as well as examination with a flexible camera through the urethra, called
urethroscopy Urethroscopy is examination of the interior of the urethra, and sometimes also the bladder
The bladder () is a hollow organ in humans and other vertebrates that stores urine from the kidneys. In placental mammals, urine enters the bladder via ...
. If a malignancy is found, a
biopsy
A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...
will be taken, and a
CT scan
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...
will be performed of other body parts (a
CT scan of the chest, abdomen and pelvis) to look for additional lesions.
After the cancer is
staged, treatment may involve
chemotherapy
Chemotherapy (often abbreviated chemo, sometimes CTX and CTx) is the type of cancer treatment that uses one or more anti-cancer drugs (list of chemotherapeutic agents, chemotherapeutic agents or alkylating agents) in a standard chemotherapy re ...
.
Injury
Passage of
kidney stone
Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cr ...
s through the urethra can be painful. Damage to the urethra, such as by kidney stones, chronic infection, cancer, or from catheterisation, can lead to narrowing, called a
urethral stricture. The location and structure of the narrowing can be investigated with a
medical imaging
Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to revea ...
scan in which dye is injected through the urinary meatus into the urethra, called a
retrograde urethrogram.
Additional forms of imaging, such as
ultrasound
Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply ...
,
computed tomography
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...
and
magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...
may also be used to provide further details.
Injuries to the urethra (e.g., from a
pelvic fracture)
Foreign bodies in the urethra are uncommon, but there have been medical case reports of self-inflicted injuries, a result of insertion of foreign bodies into the urethra such as an electrical wire.
Other
Hypospadias
Hypospadias is a common malformation in fetal development of the penis in which the urethra does not open from its usual location on the head of the penis. It is the second-most common birth defect of the male reproductive system, affecting about ...
and
epispadias
Epispadias is a birth defect in which the urethra fails to fully develop, resulting in urine leaving the body from an abnormal site. In males, this may be an opening on the upper aspect of the penis, and in females when the urethra develops too ...
are forms of abnormal development of the urethra in the male, where the
meatus is not located at the
distal
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
end of the penis (it occurs lower than normal with hypospadias, and higher with epispadias). In a severe
chordee
Chordee is a condition in which the Glans penis, head of the Human penis, penis curves downward or upward, at the junction of the head and Body of penis, shaft of the penis. The curvature is usually most obvious during erection, but resistance to ...
, the urethra can develop between the penis and the scrotum.
Catheterisation
A tube called a
catheter
In medicine, a catheter ( ) is a thin tubing (material), tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. ...
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
Neurology (from , "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the s ...
cause such as multiple sclerosis
Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...
.[ Complications that are associated with catheter insertion can include catheter-associated infections, injury to the urethra or nearby structures, or pain.]
Other animals
In all mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s, with the exception of monotreme
Monotremes () are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified ...
s, 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. In marsupial
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...
s, the female's urethra empties into the urogenital sinus
The urogenital sinus is a body part of a human or other Placentalia, placental only present in the development of the urinary system, development of the urinary and development of the reproductive organs, reproductive organs. It is the ventral p ...
.
History
The word "urethra" comes from the Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
οὐρήθρα – ''ourḗthrā''. The stem "uro" relating to urination, with the structure described as early as the time of Hippocrates
Hippocrates of Kos (; ; ), also known as Hippocrates II, was a Greek physician and philosopher of the Classical Greece, classical period who is considered one of the most outstanding figures in the history of medicine. He is traditionally referr ...
. 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
Aelius Galenus or Claudius Galenus (; September 129 – AD), often Anglicization, anglicized as Galen () or Galen of Pergamon, was a Ancient Rome, Roman and Greeks, Greek physician, surgeon, and Philosophy, philosopher. Considered to be one o ...
in the second century AD. Surgery to the urethra to remove kidney stones has been described since at least the first century AD by Aulus Cornelius Celsus.
Additional images
File:Prostatelead.jpg, Position of the urethra in males
File:Gray1155 a.png, Transverse section of the penis
File:Male urinary meatus.jpg, Male urethral opening on glans penis
In male human anatomy, the glans penis or penile glans, commonly referred to as the glans, (; from Latin ''glans'' meaning "acorn") is the bulbous structure at the Anatomical terms of location#Proximal and distal, distal end of the human penis ...
File:Skenes gland.jpg, Female urethral opening within vulval vestibule
The vulval vestibule (also known as the vulvar vestibule or vestibule of vagina) is the part of the vulva between the labia minora. At the innermost part are the vaginal introitus and urinary meatus. The Bartholin's and Skene's glands each ha ...
File:1116 Muscle of the Female Perineum.png, Muscles of the female perineum
File:Slide12BLA.JPG, Urethra. Deep dissection. Serial cross section.
File:Penis lateral cross section.jpg, Diagram which depicts the membranous urethra and the spongy urethra of a male
File:Female vaginal anatomy.jpg
See also
* Perineal urethra
* Vulvovaginal health
* Urethral glands
* Urethral sponge
The urethral sponge is a spongy cushion of biological tissue, tissue, found in the lower genitals, genital area of females, that sits against both the pubic bone and vaginal wall, and surrounds the urethra.
Functions
The urethral sponge is com ...
* Sexual stimulation: Urethral sounding and Urethral intercourse
* Urethrorrhagia
* Urethrotomy
* Urethrectomy
* Internal urethral orifice
References
External links
* "Male Urethra"
{{Authority control
Mammal reproductive system
Urinary system
Human reproductive system