RT Book, Section
A1 Suneja, Manish
A1 Szot, Joseph F.
A1 LeBlond, Richard F.
A1 Brown, Donald D.
SR Print(0)
ID 1189114451
T1 The Urinary System
T2 DeGowin’s Diagnostic Examination, 11e
YR 2020
FD 2020
PB McGraw Hill
PP New York, NY
SN 9781260134872
LK accessmedicine.mhmedical.com/content.aspx?aid=1189114451
RD 2024/04/25
AB The  urinary  system  includes  the  kidneys,  renal  pelvis,  ureters,  urinary  bladder,  and  urethra.  The  kidney  filters  the  blood  at  the  glomerulus,  reabsorbs  and  secretes  solutes  and  fluid  in  the  renal  tubules,  and  concentrates  the  urine  in  the  medullary  collecting  ducts.  Urine  passes  down  the  ureters  to  the  bladder  by  gravity  and  peristalsis  filling  the  urinary  bladder.  At  the  ureterovesical  junction  the  ureters  are  compressed  by  detrusor  muscle  tone  as  they  pass  obliquely  through  the  bladder  wall.  This  compression  increases  during  detrusor  contraction  preventing  urine  from  refluxing  into  the  ureters.  The  detrusor  actively  relaxes  as  the  bladder  fills  maintaining  a  low  pressure  within  the  bladder  until  it  reaches  capacity.  Further  filling  stretches  the  bladder  wall  rapidly  increasing  intravesical  pressure.  The  urethra  exits  the  bladder  through  the  urethral  sphincter  and  the  urogenital  septum.  This  sphincter  has  involuntary  smooth  muscle  under  parasympathetic  and  sympathetic  control,  and  voluntary  striated  muscle  innervated  via  the  lumbosacral  plexus.  Continence  requires  tonic  urethral  sphincter  smooth  muscle  contraction  and  active  inhibition  of  detrusor  contraction.  Voiding  requires  detrusor  contraction  and  simultaneous  relaxation  of  the  urethral  sphincter  muscles.