Detrusor urinae muscle
Encyclopedia
The detrusor urinae muscle, also detrusor muscle, muscularis propria of the urinary bladder and (less precise) muscularis propria, contracts when urinating to squeeze out urine
. Otherwise, it remains relaxed to allow the bladder
to fill. Related are the urethral sphincter
muscles which envelop the urethra to control the flow of urine when they contract.
in both sexes (musculi pubovesicales), and in the male from the adjacent part of the prostate
and its capsule. These fibers pass, in a more or less longitudinal manner, up the inferior surface of the bladder
, over its apex
, and then descend along its fundus to become attached to the prostate in the male, and to the front of the vagina
in the female. At the sides of the bladder the fibers are arranged obliquely and intersect one another.
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...
. Otherwise, it remains relaxed to allow the 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 fill. Related are the 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...
muscles which envelop 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 pubisBody of pubic bone
The body of pubic boneforms the wide, strong, medial and flat portion of the pubic bone which unite in the pubic symphysis.The rough superior edge of the corpus, the pubic crest, ends laterally in the pubic tubercle...
in both sexes (musculi pubovesicales), and in the male from the adjacent part of the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
and its capsule. These fibers pass, in a more or less longitudinal manner, up the inferior surface of the 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...
, over its apex
Apex of urinary bladder
The apex of urinary bladder is directed forward toward the upper part of the pubic symphysis, and from it the middle umbilical ligament is continued upward on the back of the anterior abdominal wall to the umbilicus. The peritoneum is carried by it from the vertex of the bladder on to the...
, and then descend along its fundus to become attached to the prostate in the male, and to the front of 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...
in the female. At the sides of the bladder the fibers are arranged obliquely and intersect one another.