Urethral crest

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Urethral crest
Gray1142.png
The male urethra laid open on its anterior (upper) surface. (Urethral crest labeled at upper right.)
Prostatic urethra.svg
Dissection of prostate showing prostatic urethra and urethral crest on posterior wall
Details
Identifiers
Latin crista urethralis urethrae masculinae, crista urethralis urethrae femininae
TA98 A09.2.03.004
A09.4.02.007
TA2 3430, 3446
FMA 19718
Anatomical terminology

The urethral crest is an anatomical feature present in the urinary system of both males and females.

Contents

In males, the urethral crest is known as the crista urethralis masculinae, or the crista phallica, and is a longitudinal fold on the posterior wall of the urethra extending from the uvula of the bladder through the prostatic urethra. [1] It is from 15 to 17 mm. in length, and about 3 mm. in height, and contains muscular and erectile tissue. When distended, it may serve to prevent the passage of the semen backward into the bladder. [2]

In females, it is known as the crista urethralis femininae, and is a conspicuous longitudinal fold of mucosa on the posterior wall of the urethra. [3]

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The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.

Bulbospongiosus muscle

The bulbospongiosus muscle is one of the superficial muscles of the perineum. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis. In females, it covers the vestibular bulb.

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Posterior urethral valve Medical condition

Posterior urethral valve (PUV) disorder is an obstructive developmental anomaly in the urethra and genitourinary system of male newborns. A posterior urethral valve is an obstructing membrane in the posterior male urethra as a result of abnormal in utero development. It is the most common cause of bladder outlet obstruction in male newborns. The disorder varies in degree, with mild cases presenting late due to milder symptoms. More severe cases can have renal and respiratory failure from lung underdevelopment as result of low amniotic fluid volumes, requiring intensive care and close monitoring. It occurs in about one in 8,000 babies.

Spongy urethra

The spongy urethra is the longest part of the male urethra, and is contained in the corpus spongiosum of the penis.

Membranous urethra

The membranous urethra or intermediate part of male urethra is the shortest, least dilatable, and, with the exception of the urinary meatus, the narrowest part of the urethra.

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, the uvula vesicae, caused by the middle lobe of the prostate.

Seminal colliculus

The seminal colliculus, or verumontanum, of the prostatic urethra is a landmark distal to the entrance of the ejaculatory ducts. Verumontanum is translated from Latin to mean 'mountain ridge', a reference to the distinctive median elevation of urothelium that characterizes the landmark on magnified views. Embryologically, it is derived from the uterovaginal primordium. The landmark is important in classification of several urethral developmental disorders. The margins of seminal colliculus are the following:

Detrusor muscle Muscle of the bladder which expels urine when it contracts

The detrusor muscle, also detrusor urinae muscle, muscularis propria of the urinary bladder and muscularis propria, is smooth muscle found in the wall of the bladder. The detrusor muscle remains relaxed to allow the bladder to store urine, and contracts during urination to release urine. Related are the urethral sphincter muscles which envelop the urethra to control the flow of urine when they contract.

The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically described together as the urogenital or genitourinary system.

Urethral sphincters

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 male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.

Internal urethral sphincter

The internal urethral sphincter is a urethral sphincter muscle which constricts the internal urethral orifice. It is located at the junction of the urethra with the urinary bladder and is continuous with the detrusor muscle, but anatomically and functionally fully independent from it. It is composed of smooth muscle, so it is under the control of the autonomic nervous system, specifically the sympathetic nervous system.

References

  1. "Crista urethralis masculinae". biology-online.org.
  2. "Urethral Crest". Archived from the original on 2007-02-20. Retrieved 2014-11-15.
  3. "Crista urethralis femininae". biology-online.org.