Urethra
Overview
In anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

, the urethra (from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 οὐρήθρα - ourethra) is a tube that connects the urinary bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...

 to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

, and carries semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 as well as urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

. In females, the urethra is shorter and emerges above the vaginal opening.

The external urethral sphincter
Urethral sphincter
The term urethral sphincter refers to one of two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are the external urethral sphincter and the internal urethral sphincter...

 is a striated muscle that allows voluntary control over urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...

.
In the human female, the urethra is about 1.5 – long and exits the body between the clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

 and the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

, extending from the internal to the external urethral orifice.
Encyclopedia
In anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

, the urethra (from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 οὐρήθρα - ourethra) is a tube that connects the urinary bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...

 to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

, and carries semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 as well as urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

. In females, the urethra is shorter and emerges above the vaginal opening.

The external urethral sphincter
Urethral sphincter
The term urethral sphincter refers to one of two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are the external urethral sphincter and the internal urethral sphincter...

 is a striated muscle that allows voluntary control over urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...

.

Female urethra

In the human female, the urethra is about 1.5 – long and exits the body between the clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

 and the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

, extending from the internal to the external urethral orifice. 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. 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 urethrae (urethral sphincter)
Urethral sphincter
The term urethral sphincter refers to one of two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are the external urethral sphincter and the internal urethral sphincter...

. Somatic
Somatic nervous system
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles...

 (conscious) innervation of the external urethral sphincter is supplied by the pudendal nerve
Pudendal nerve
The pudendal nerve is a sensory and somatic nerve in the pelvic region which is a large branch of the sacral plexus that innervates the external genitalia of both sexes, as well as sphincters for the bladder and the rectum...

. 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. The area above and on both sides of the female urethra is thought by some to be sexually sensitive and is sometimes referred to as the U-spot or urethral erogenous zone.

Male urethra

In the human male, the urethra is about 8 inches (20.3 cm) long and opens at the end of the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...

. The urethra provides an exit for urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 as well as semen
Semen
Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 during ejaculation
Ejaculation
Ejaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...

.

The urethra is divided into four parts in men, named after the location:
| prostatic urethra
Prostatic urethra
The prostatic urethra, the widest and most dilatable part of the urethra canal, is about 3 cm. long.It runs almost vertically through the prostate from its base to its apex, lying nearer its anterior than its posterior surface; the form of the canal is spindle-shaped, being wider in the middle...

 >
Region Description Epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...


>-
| pre-prostatic urethra
Pre-prostatic urethra
The pre-prostatic urethra is one of the four parts of the male urethra. The pre-prostatic urethra is also known as the intramural urethra, as it is the portion of the urethra which passes almost vertically through the wall of the urinary bladder, before it enters the prostate gland.Both the length...

 
This is the intramural part of the urethra and varies between 0.5 and 1.5 cm in length depending on the fullness of the bladder. Transitional
Crosses through the prostate gland. There are several openings: (1) the ejaculatory duct
Ejaculatory duct
-Anatomy:The ejaculatory ducts are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra at the Colliculus seminalis...

 receives sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

 from the vas deferens
Vas deferens
The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....

 and ejaculate fluid from the seminal vesicle
Seminal vesicle
The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals...

, (2) several prostatic ducts
Prostatic ducts
The prostatic ducts open into the floor of the prostatic portion of the urethra, and are lined by two layers of epithelium, the inner layer consisting of columnar and the outer of small cubical cells....

 where fluid from the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....

 enters and contributes to the ejaculate, (3) the prostatic utricle
Prostatic utricle
The prostatic utricle is a small indentation located in the prostatic urethra, at the apex of the urethral crest, on the seminal colliculus , laterally flanked by openings of the ejaculatory ducts...

, which is merely an indentation. These openings are collectively called the verumontanum.
>-
| membranous urethra
Membranous urethra
The intermediate part of male urethra is the shortest, least dilatable, and, with the exception of the external orifice, the narrowest part of the canal....

 
A small (1 or 2 cm) portion passing through the external urethral sphincter. This is the narrowest part of the urethra. It is located in the deep perineal pouch
Deep perineal pouch
The deep perineal pouch is a human anatomical term that refers to the space enclosed in part by the perineum, and located superior to the perineal membrane.-Structure:...

. The bulbourethral glands (Cowper's gland) are found posterior to this region but open in the spongy urethra
Spongy urethra
The spongy urethra is the longest part of the male urethra, and is contained in the corpus spongiosum urethraeæ....

.
>-
| spongy urethra
Spongy urethra
The spongy urethra is the longest part of the male urethra, and is contained in the corpus spongiosum urethraeæ....

 (or penile urethra)
Runs along the length of the penis on its ventral (underneath) surface. It is about 15–16 cm in length, and travels through the corpus spongiosum
Corpus spongiosum
Corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis...

. The ducts from the urethral gland
Urethral gland
-External links:* *...

 (gland of Littre) enter here. The openings of the bulbourethral glands are also found here. Some textbooks will subdivide the spongy urethra into two parts, the bulbous and pendulous urethra.
Pseudostratified columnar – proximally, Stratified squamous – distally


The length of a male's urethra, and the fact it contains a prominent bend, makes catheter
Urinary catheterization
In urinary catheterization , a latex, polyurethane or silicone tube known as a urinary catheter is inserted into a patient's bladder via his or her urethra. Catheterization allows the patient's urine to drain freely from the bladder for collection. It may be used to inject liquids used for...

ization more difficult. The integrity of the urethra can be determined by a procedure known as retrograde urethrogram
Retrograde urethrogram
A retrograde urethrogram is a routine radiologic procedure used to image the integrity of the urethra.Hence a retrograde urethrogram is essential for diagnosis of urethral injury, or urethral stricture.-Process:...

.

Histology

The epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

 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 urethral orifice
External urethral orifice
External urethral orifice can refer to:* External urethral orifice * External urethral orifice...

.

There are small mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

-secreting urethral glands, that help protect the epithelium from the corrosive urine.

Length of the urethrae

The female urethra is about 4 cm in length. 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.

Medical problems of the urethra

  • Hypospadias
    Hypospadias
    Hypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus...

     and epispadias
    Epispadias
    An epispadias is a rare type of malformation of the penis in which the urethra ends in an opening on the upper aspect of the penis. It can also develop in females when the urethra develops too far anteriorly...

     are forms of abnormal development of the urethra in the male, where the meatus
    Urinary meatus
    The urinary meatus is an orifice of the urethra. It is the point at which urine and, in males, semen exits the urethra. The meatus features varying degrees of sensitivity to the touch among males and females....

     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
    Chordee
    Chordee is a condition in which the head of the penis curves downward or upward, at the junction of the head and shaft of the penis. The curvature is usually most obvious during erection, but resistance to straightening is often apparent in the flaccid state as well. In many cases but not all,...

    , the urethra can develop between the penis
    Penis
    The penis is a biological feature of male animals including both vertebrates and invertebrates...

     and the scrotum
    Scrotum
    In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...

    .
  • Infection of the urethra is urethritis
    Urethritis
    Urethritis is inflammation of the urethra. The most common symptom is painful or difficult urination.-Causes:The disease is classified as either gonococcal urethritis, caused by Neisseria gonorrhoeae, or non-gonococcal urethritis , most commonly caused by Chlamydia trachomatis...

    , said to be more common in females than males. Urethritis is a common cause of dysuria
    Dysuria
    In medicine, specifically urology, dysuria refers to painful urination.Difficult urination is also sometimes described as dysuria.It is one of a constellation of irritative bladder symptoms, which includes urinary frequency and haematuria....

     (pain when urinating).
  • Related to urethritis is so called urethral syndrome
    Urethral syndrome
    Urethral syndrome is defined as symptoms suggestive of a lower urinary tract infection but in the absence of significant bacteruria with a conventional pathogen...

  • Passage of kidney stone
    Kidney stone
    A kidney stone, also known as a renal calculus is a solid concretion or crystal aggregation formed in the kidneys from dietary minerals in the urine...

    s through the urethra can be painful, which can lead to urethral stricture
    Urethral stricture
    A urethral stricture is a narrowing of the urethra caused by injury or disease such as urinary tract infections or other forms of urethritis.-Signs and symptoms:...

    s.
  • Cancer of the urethra.
  • 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.

Investigations

  • Endoscopy
    Endoscopy
    Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an endoscope , an instrument used to examine the interior of a hollow organ or cavity of the body. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ...

     of the bladder via the urethra is called cystoscopy
    Cystoscopy
    Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope.Diagnostic cystoscopy is usually carried out with local anaesthesia...

    .
  • Urine cytology
    Urine cytology
    Urine typically contains epithelial cells shed from the urinary tract. Urine cytology evaluates this urinary sediment for the presence of cancerous cells from the lining of the urinary tract, and it is a convenient noninvasive technique for follow-up analysis of patients treated for urinary tract...

    .

Sexual physiology

The male urethra is the conduit for semen during sexual intercourse
Sexual intercourse
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...

. It also serves as a passage for urine to flow.
Urine typically contains epithelial cells shed from the urinary tract. Urine cytology evaluates this urinary sediment for the presence of cancerous cells from the lining of the urinary tract, and it is a convenient noninvasive technique for follow-up analysis of patients treated for urinary tract cancers. For this process, urine must be collected in a reliable fashion, and if urine samples are inadequate, the urinary tract can be assessed via instrumentation. In urine cytology, collected urine is examined microscopically. One limitation, however, is the inability to definitively identify low-grade cancer cells and urine cytology is used mostly to identify high-grade tumors.

See also

  • Perineal urethra
    Perineal urethra
    A perineal urethra is a human urethral opening that is located on the perineum rather than at the tip of the phallus. Urethral position is an aspect of human sexual dimorphism. A phallic urethra is typical of male anatomy and a perineal urethra is typical of female anatomy...

  • Vulvovaginal health
    Vulvovaginal health
    Vulvovaginal health is the health and sanitation of the human female vulva and vagina.-Conditions:Problems affecting this area include:*Infection with Candida albicans...

  • Urethral sponge
    Urethral sponge
    The urethral sponge is a spongy cushion of tissue, found in the lower genital area of women, that sits against both the pubic bone and vaginal wall, and surrounds the urethra.-Functions:...

  • G-spot
    G-spot
    The Gräfenberg Spot, often called the G-Spot, is a bean-shaped area of the vagina. Many women report that it is an erogenous zone which, when stimulated, can lead to strong sexual arousal, powerful orgasms and female ejaculation...

  • Sexual stimulation: Urethral sounding
    Urethral sounding
    Sounding or urethral sounding is the medical use of probes called sounds to increase the inner diameter of the urethra and to locate obstructions in it...

     and Urethral intercourse
    Urethral intercourse
    Urethral intercourse refers to the penetration of the female urethra by an object such as a penis or finger. It is not to be confused with urethral sounding, the act of inserting a specialized medical tool into the urethra as a form of sexual or fetishistic activity.The untrained insertion of...

  • Urethrotomy
    Urethrotomy
    A urethrotomy is an operation which involves incision of the urethra, especially for relief of a stricture. It is most often performed in the outpatient setting, with the patient being discharged from the hospital or surgery center within six hours from the procedure's inception.Urethrotomy is a...

  • Urethral Stricture
    Urethral stricture
    A urethral stricture is a narrowing of the urethra caused by injury or disease such as urinary tract infections or other forms of urethritis.-Signs and symptoms:...

  • Cystoscopy
    Cystoscopy
    Cystoscopy is endoscopy of the urinary bladder via the urethra. It is carried out with a cystoscope.Diagnostic cystoscopy is usually carried out with local anaesthesia...

  • Internal urethral orifice
    Internal urethral orifice
    The internal urethral orifice is the opening of the urinary bladder into the urethra. It is placed at the apex of the trigonum vesicae, in the most dependent part of the bladder, and is usually somewhat crescent-shaped; the mucous membrane immediately behind it presents a slight elevation in males,...


External links

"Male Urethra"
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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