urethral

• adj.

• 尿道の

関

urethra

　

WordNet

1. of or relating to the urethra
2. duct through which urine is discharged in most mammals and which serves as the male genital duct

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1. 尿道

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/04/07 21:05:25」(JST)

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Urethra
The urethra transports urine from the bladder to the outside of the body. This image shows (a) a female urethra and (b) a male urethra.
Details
Precursor	Urogenital sinus
Artery	Inferior vesical artery Middle rectal artery Internal pudendal artery
Vein	Inferior vesical vein Middle rectal vein Internal pudendal vein
Nerve	Pudendal nerve Pelvic splanchnic nerves Inferior hypogastric plexus
Lymph	Internal iliac lymph nodes Deep inguinal lymph nodes
Identifiers
Latin	urethra vagina; feminina (female); urethra masculina (male)
Greek	οὐρήθρα
MeSH	A05.360.444.492.726
Dorlands /Elsevier	Urethra
TA	A08.4.01.001F A08.5.01.001M
FMA	19667
Anatomical terminology [edit on Wikidata]

In anatomy, the urethra (from Greek οὐρήθρα – ourḗthrā) is a tube that connects the urinary bladder to the urinary meatus for the removal of fluids from the body. In male placental mammals, the urethra travels through the penis, and carries semen as well as urine. In female placental mammals, the urethra is shorter and emerges at the female external urethral orifice above the vaginal opening.

Female placental mammals use their urethra only for urinating, but male placental mammals use their urethra for both urination and ejaculation. The external urethral sphincter is a striated muscle that allows voluntary control over urination.

Anatomy

Female

Urethra is number 2, dark yellow

In the human female, the urethra is about 1.9 inches (4.8 cm) to 2 inches (5.1 cm) long and exits the body between the clitoris and the vagina, 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 2/3rds is lined by transitional epithelium cells while distal 1/3rd is lined by stratified squamous epithelium cells.

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 urethral sphincter. Somatic (conscious) 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

See also: Category:Male urethra.

In the human male, the urethra is about 8 inches (20 cm) long and opens at the end of the external urethral meatus.{{}} The urethra provides an exit for urine as well as semen during ejaculation.

The urethra is divided into four parts in men, named after the location:

Region	Description	Epithelium
pre-prostatic urethra	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
prostatic urethra	Crosses through the prostate gland. There are several openings: (1) the ejaculatory duct receives sperm from the vas deferens and ejaculate fluid from the seminal vesicle, (2) several prostatic ducts where fluid from the prostate enters and contributes to the ejaculate, (3) the prostatic utricle, which is merely an indentation. These openings are collectively called the verumontanum.	Transitional
membranous urethra	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. The bulbourethral glands (Cowper's gland) are found posterior to this region but open in the spongy urethra.	Pseudostratified columnar
spongy urethra (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. The ducts from the urethral gland (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. The urethral lumen runs effectively parallel to the penis, except at the narrowest point, the external urethral meatus, where it is vertical. This produces a spiral stream of urine and has the effect of cleaning the external urethral meatus. The lack of an equivalent mechanism in the female urethra partly explains why urinary tract infections occur so much more frequently in females.	Pseudostratified columnar – proximally, Stratified squamous – distally

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.

Histology

The epithelium of the urethra starts off as transitional cells as it exits the bladder. Further along the urethra there are pseudostratified columnar and stratified columnar epithelia, then stratified squamous cells near the external urethral orifice.

There are small mucus-secreting urethral glands, that help protect the epithelium from the corrosive urine.

Physiology

See also: 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.

Sexual physiology

The male urethra is the conduit for semen during sexual intercourse. 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 is the inability to definitively identify low-grade cancer cells and urine cytology is used mostly to identify high-grade tumors.

Clinical significance

Micrograph of urethral cancer (urothelial cell carcinoma), a rare problem 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, which can lead to urethral strictures.
• Injuries to the urethra (e.g., from a pelvic fracture)
• 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

As the urethra is an open vessel with a lumen, investigations of the genitourinary tract may involve the urethra. Endoscopy of the bladder may be conducted by the urethra, called cystoscopy.

• Urine cytology.

Catheterization

During a hospital stay or surgical procedure, a catheter may be inserted through the urethra to drain urine from the bladder. The length of a male's urethra, and the fact it contains a prominent bend, makes catheterization more difficult. The integrity of the urethra can be determined by a procedure known as retrograde urethrogram.

Additional images

• Position of the urethra in males

• Transverse section of the penis.

• Male urethral opening

• Muscles of the female perineum

• Urethra. Deep dissection.Serial cross section.

See also

• Perineal urethra
• Vulvovaginal health
• Urethral sponge
• Sexual stimulation: Urethral sounding and Urethral intercourse
• Urethrotomy
• Internal urethral orifice

References

External links

• Histology at KUMC epithel-epith07 "Male Urethra"

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

• 1. 尿道カルンクル urethral caruncle
• 2. 女性における尿道憩室 urethral diverticulum in women
• 3. 男性における尿道癌 urethral cancer in men
• 4. 女性における尿道癌 urethral cancer in women
• 5. 男性における尿道狭窄疾患の治療 treatment of urethral stricture disease in men

English Journal

• The Single-Incision Sling to Treat Female Stress Urinary Incontinence: A Dynamic Computational Study of Outcomes and Risk Factors.

• Peng Y, Khavari R, Nakib NA, Stewart JN, Boone TB, Zhang Y.
• Journal of biomechanical engineering.J Biomech Eng.2015 Sep 1;137(9). doi: 10.1115/1.4030978. Epub 2015 Jul 14.
• Dynamic behaviors of the single-incision sling (SIS) to correct urethral hypermobility are investigated via dynamic biomechanical analysis using a computational model of the female pelvis, developed from a female subject's high-resolution magnetic resonance (MR) images. The urethral hypermobility is
• PMID 26142123

• Renal oligo- and anhydramnios: cause, course and outcome-a single-center study.

• Spiro JE1, Konrad M, Rieger-Fackeldey E, Masjosthusmann K, Amler S, Klockenbusch W, Schmitz R.
• Archives of gynecology and obstetrics.Arch Gynecol Obstet.2015 Aug;292(2):327-36. doi: 10.1007/s00404-015-3648-7. Epub 2015 Feb 13.
• PURPOSE: To evaluate the outcome of patients with renal oligohydramnios and explore the impact of patient variables on outcome and prognosis.METHODS: A retrospective single-center study was conducted analyzing 104 pregnancies complicated by oligohydramnios of renal origin from 2001 to 2011. Statisti
• PMID 25676656

• Primary malignant melanoma of the urethra detected by urine cytology in a male patient.

• DeSimone RA1, Hoda RS1.
• Diagnostic cytopathology.Diagn Cytopathol.2015 Aug;43(8):680-2. doi: 10.1002/dc.23258. Epub 2015 Feb 19.
• PMID 25694368

Japanese Journal

• 包茎専門美容外科クリニックにおける術後尿道欠損の1例 (特集 美容医療の合併症から学ぶ(2)骨切り他編)

• 形成外科 58(10), 1102-1106, 2015-10
• NAID 40020605001

• S状結腸癌による膀胱腸瘻から尿道瘻孔を形成し陰嚢内膿瘍を認めた1例

• 泌尿器科紀要 = Acta urologica Japonica 61(9), 375-378, 2015-09
• NAID 120005668041

• 腹腔鏡内視鏡合同手術（Laparoscopy and Endoscopy Cooperative Surgery；LECS） を施行したＳ状結腸膀胱瘻の1例

• 岡山医学会雑誌 127(2), 123-126, 2015-08-03
• NAID 120005649237

Related Pictures

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★リンクテーブル★

拡張検索	「urethral neoplasm」「transurethral」

「urethral neoplasm」

　　[★]

尿道腫瘍、尿道新生物

関

urethral cancer

「transurethral」

　　[★]

• adj.

• 経尿道の

関

per urethra