The detrusor muscle, also detrusor urinae muscle, muscularis propria of the urinary bladder and (less precise)

muscularis propria The muscular layer (muscular coat, muscular fibers, muscularis propria, muscularis externa) is a region of muscle in many organs in the vertebrate body, adjacent to the submucosa. It is responsible for gut movement such as peristalsis. The Latin, ...

, is

smooth muscle Smooth muscle is an involuntary non- striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit ...

found in the wall of the

bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine en ...

. The detrusor muscle remains relaxed to allow the bladder to store

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellul ...

, and contracts during

urination Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

to release urine. Related are 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 male or female external urethral sphincter and the internal urethral sphincter. When either of th ...

muscles which envelop the

urethra 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 ...

to control the flow of urine when they contract.

Structure

The fibers of the detrusor muscle arise from the posterior surface of the body of the pubis in both sexes (musculi pubovesicales), and in the male from the adjacent part of the

prostate The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found only in some mammals. It differs between species anatomically, chemically, and phys ...

. These fibers pass, in a more or less

longitudinal Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian * Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, ...

manner, up the inferior surface of the

, over its

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

, and then descend along its fundus to become attached to the prostate in the male, and to the front of the

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

in the female. At the sides of the bladder the fibers are arranged obliquely and intersect one another. The 3 layers of muscles are arranged longitudinal-circular-longitudinal from innermost to outermost.

Function

During urination, the detrusor muscle is contracted via

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of ...

branches from the

pelvic splanchnic nerves Pelvic splanchnic nerves or nervi erigentes are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the organs of the pelvic cavity. Structure The pelvic splanchnic nerves arise from th ...

to empty the bladder. At other times, the muscle is kept relaxed via sympathetic branches from the

inferior hypogastric plexus The inferior hypogastric plexus (pelvic plexus in some texts) is a network () of nerves that supplies the organs of the pelvic cavity. The inferior hypogastric plexus gives rise to the prostatic plexus in males and the uterovaginal plexus in femal ...

to allow the bladder to fill.

Clinical significance

In older adults over 60 years in age, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable

urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladd ...

. The mucosa of the urinary bladder may herniate through the detrusor muscle. This is most often an acquired condition due to high pressure in the urinary bladder, damage, or existing connective tissue disorders.

References

External links

*
Detrusor myectomy for detrusor overactivity: 1-year follow-up
{{Authority control Urinary system Muscles of the torso

Structure

Function

Clinical significance

See also

References

External links