urinary system

• Components of the urinary system

  • Two kidneys
  • Two ureters
  • One bladder
  • One urethra

  
• Urinary system


  Excretory system for urine and the wastes it carries

  
• Function of the urinary system

  1. Extracts wastes from the bloodstream

  2. Converts them to urine

  3. Transports and eliminates urine

  
• Kidneys


  • Bean-shaped organs located at the back of the abdominal cavity, lying on each side of the spinal column just above the waistline

  
• Layers surrounding each kidney

  • True capsule (smooth, fibrous membrane adhering to the kidney surface)
  • Perirenal fat (adipose tissue surrounding each kidney)
  • Renal fascia (fibrous tissue that anchors the kidney to surrounding structures)

  
• Hilum


  Notch in the concave area of the kidney where the renal artery, renal vein, nerves, and lymphatic vessels enter and leave, and the ureter widens into the renal pelvis

  
• Renal cortex


  Outside portion of the kidney

  
• Renal medulla

  Inside portion of the kidney

  
• Nephrons


  • Structural and functional units of the kidney, each containing a Bowman's capsule and a glomerulus

  
• Each kidney contains about 1 million nephrons
• Glomerulus


  Part of the nephron that filters approximately 1,000 ml of blood per minute
• The waste is mixed with water to create urine: 5% solids in 95% water
• Substances removed by the nephron

  • Urea
  • Uric acid
  • Creatinine
  • Excess sodium
  • Excess chloride
  • Excess potassium ions
  • Ketone bodies
• Ureter


  • Narrow, muscular tube about 11 inches in length and 3/8 inch in diameter, with 3 layers: inner mucous membrane, middle smooth muscle, and outer fibrous tissue

  
• Bladder


  • Muscular, membranous sac that serves as a reservoir for urine, with an apex, neck, and triangular trigone near the base

  
• An adult feels the need to void when the bladder contains about 300 ml or 1 ¼ cups

  
• An average of 1,000 ml of urine is voided daily
• Urine is clear to light yellow in color with a faint odor and slightly acidic pH
• Bladder wall


  • Inner mucous layer, outside fibrous layer, and two inner muscle layers that thin and expand as the bladder fills with urine

  
• Urethra


  • Extends from the bladder to the outside opening of the body, about 7.8" long in males and 1.2" long in females, transporting both urine and semen in males, only urine in females

  
• Urinalysis


  Laboratory procedure involving the physical, chemical and microscopic examination of a urine sample
• Changes occur as urine is left standing, so the urinalysis is performed within one hour of voiding

  
• Catheterization


  Insertion of a plastic tube through the urethra into the bladder for free and complete drainage of urine, using a Robinson catheter for temporary placement or a Foley catheter with a balloon tip for longer-term use

  
• Urinary incontinence


  Loss of bladder control, ranging from leakage to uncontrollable wetting, becoming more common with age, caused by weak bladder muscles (stress incontinence) or overactive bladder, as well as prostate problems and nerve damage