Muscle tone. Definition. noun. (1) The muscle in a steady partially contracted state caused by the successive flow of nerve impulses. (2) The amount of tension or resistance to movement in a muscle. Supplement. Muscle tone or tonus helps in maintaining body posture.
Hydronephrosis is the distention of the pelvis and calyces of one or both kidneys, resulting in thinning of the renal tubules because of obstructed urinary flow. When the obstruction is a stone or kink in one of the ureters, only one kidney is damaged.
Long-standing distention of the renal pelvis and ureter can also inhibit the rhythmic muscular contractions that normally move urine down the ureter from the kidney to the bladder (peristalsis). Scar tissue may then replace the normal muscular tissue in the walls of the ureter, resulting in permanent damage.