Urinalysis

• Organs of the urinary system

  • Kidneys
  • Ureters
  • Urinary bladder
  • Urethra
• Kidneys


  • Produce the enzyme renin to help regulate blood pressure
  • Release the hormone erythropoietin to stimulate red blood cell production
• Kidney structure


  • Kidney cells convert vitamin D to its active form
  • Lie against the dorsal body wall in a retroperitoneal position
  • Protected by the lower part of the rib cage
  • Adult kidney size: 12 cm long, 6 cm wide, and 3 cm thick
• Protective layers of the kidney

  • Fibrous capsule
  • Perirenal fat capsule
  • Renal fascia
• Regions of the kidney

  • Renal cortex
  • Renal medulla
  • Renal pyramids / Medullary pyramids
  • Renal columns
  • Renal pelvis
  • Calyces
• Renal artery


  Supplies the kidney with arterial blood
• Blood supply cycle of the kidney

  1. Renal artery divides into segmental arteries

  2. Segmental arteries give off interlobar arteries

  3. Interlobar arteries reach the cortex and give off arcuate arteries

  4. Arcuate arteries give off cortical radiate arteries to supply the renal cortex

  5. Venous blood flows from cortical radiate veins to arcuate veins to interlobar veins to the renal vein
• Nephron


  The structural and functional unit of the kidneys
• Main structures of a nephron

  • Renal corpuscle
  • Renal tubule
• Renal corpuscle


  Consists of a glomerulus and Bowman's capsule
• Glomerulus


  Knot of capillaries; filtering unit of the kidney
• Bowman's capsule


  Cup-shaped hollow structure that surrounds the glomerulus
• Regions of the renal tubule

  • Proximal convoluted tubule (PCT)
  • Nephron loop or loop of Henle
  • Distal convoluted tubule (DCT)
• Types of nephrons


  • Cortical nephrons
  • Juxtamedullary nephrons
• Collecting ducts


  Receive urine from nephrons and deliver the final urine product into the calyces and renal pelvis
• Capillary beds in the kidney

  • Glomerulus (high-pressure)
  • Peritubular capillary bed (low pressure)
• Afferent arteriole


  Feeds blood into the glomerulus (feeder vessel)
• Efferent arteriole


  Receives the blood that has passed through the glomerulus
• Peritubular capillaries


  Arise from the efferent arterioles that drain the glomerulus; adapted for absorption instead of filtration
• Processes of urine formation

  • Glomerular filtration
  • Tubular reabsorption
  • Tubular secretion
• Glomerular filtration


  A nonselective, passive process in which fluid passes (filters) from the blood into the glomerular capsule part of the renal tubule
• Tubular reabsorption


  The process that moves solutes and water out of the filtrate and back into the bloodstream
• Tubular secretion


  The process of getting rid of substances not already in the filtrate, such as certain drugs or excess potassium ions, or as an additional means for controlling blood pH
• Nitrogenous waste products


  • Urea
  • Uric acid
  • Creatinine
• Urine characteristics


  • Color (freshly voided, pale to deep yellow, urochrome pigment)
  • Odor (aromatic, ammoniacal)
  • pH (slightly acidic)
  • Specific gravity (1.001-1.035, dilute or concentrated)
• Substances normally found in urine

  • Sodium and potassium ions
  • Urea
  • Uric acid
  • Creatinine
  • Ammonia
  • Bicarbonate ions
• Substances not normally found in urine

  • Glucose
  • Blood proteins
  • Red blood cells
  • Hemoglobin
  • White blood cells (pus)
  • Bile
• Other organs of the urinary system

  • Ureters
  • Urinary bladder
  • Urethra
• Urinary bladder


  A smooth, collapsible, muscular sac that stores urine temporarily
• Urethra


  A thin-walled tube that carries urine by peristalsis from the bladder to the outside of the body
• Sphincters of the urethra

  • Internal urethral sphincter (involuntary, smooth muscle)
  • External urethral sphincter (voluntary, skeletal muscle)
• Micturition (voiding)


  Both the internal and external urethral sphincters must open to allow voiding
• Major roles of the kidneys

  • Excreting nitrogen-containing wastes
  • Maintaining water balance of the blood
  • Maintaining electrolyte balance of the blood
  • Ensuring proper blood pH
• Anti-diuretic hormone (ADH)


  Prevents excessive water loss in the urine; released when blood volume drops by the posterior pituitary gland
• Aldosterone


  Produced by the adrenal cortex; the major factor regulating sodium ion content of the extracellular fluid and in the process helps regulate the concentration of other ions
• Renin-angiotensin mechanism


  Mediated by the juxtaglomerular apparatus; also triggers aldosterone release; regulates blood pressure
• Normal blood pH is 7.35-7.45
• Most acid-base balance is maintained by the kidneys
• Other acid-base controlling systems

  • Blood buffers
  • Respiration