3

• Ultrafiltration / Glomerular filtration

  1. Movement of substances from blood in glomerulus to capsular space due to pressure

  2. Blood in afferent arteriole contains waste/useful substances

  3. High hydrostatic pressure created in Glomerulus due to difference in diameter of afferent & efferent arteriole, cup shape of Bowman's capsule, coiled nature of glomerulus

  4. Squamous epithelium & podocytes form slit pores

  5. Under pressure small substances are forced from blood to capsular space

  6. Fluid called Glomerular filtrate

  7. Large blood cells and proteins no filtered, continue to efferent arteriole
• Tubular reabsorption

  1. Filtrate enters PCT

  2. Water moves from tubule to renal tissue & blood by osmosis

  3. Glucose, salts, useful substances actively reabsorbed

  4. Small proteins absorbed by pinocytosis

  5. Filtrate passes into Descending limb, sodium (Na) added to filtrate

  6. Na movement regulated by aldosterone

  7. Filtrate rounds Loop of Henle

  8. Enters Ascending limb, impermeable to water, Na pump mechanism pumps Na into renal tissue

  9. Water potential of filtrate increases, water potential of renal tissue lowers

  10. Filtrate enters collecting tubule, water reabsorption depends on ADH presence, certain ions may be reabsorbed

  11. With high ADH, walls of DCT more permeable to water, water moves from renal tubule to renal tissue and blood, concentrated urine produced

  12. With low ADH, water remains in renal tubules, useful substances reabsorbed, dilute urine is produced
• Tubular secretion / excretion

  Waste/substances secreted from renal tissue into tubule walls & filtrate (active process), substances too large to filter are actively pumped into DCT (e.g. H+/Bicarbonate ions)