Glomerular filtration and tubular function

• What is one of the main functions of the kidney?

  To filter the blood
• Where does filtration occur in the kidney?

  At the nephron

  
• What happens at the nephron?

  Blood and tubular system meet to produce urine

  
• How many times do the kidneys filter blood each day?

  Up to 65 times
• What are the processes that occur at the nephron?

  • Glomerular Filtration
  • Tubular reabsorption
  • Tubular secretion
  • Excretion

  
• What feeds into the glomerulus?

  Afferent arterioles
• What is the glomerulus?

  A capillary network in the kidney
• What does Bowman’s capsule do?

  Collects glomerular filtrate

  
• What do blood cells and proteins do during filtration?

  Do not pass through the glomerulus
• What percentage of plasma is filtered at the glomerulus?

  20%
• What are the three layers of the glomerular membrane?

  Capillary wall, basement membrane, Bowman’s capsule

  
• What is the function of the glomerular capillary wall?

  It has large pores that make it leaky
• What repels plasma proteins in the basement membrane?

  Negatively charged glycoproteins
• What are filtration slits?

  Gaps between podocytes in Bowman’s capsule

  
• What increases pressure in the glomerular capillaries?

  Large diameter of afferent arteriole
• What is the osmotic gradient in Bowman’s capsule?

  Large plasma proteins in capillaries

  
• What does hydrostatic pressure do in Bowman’s capsule?

  Acts against filtration

  
• What components of plasma pass through the filtration barrier?

  All except cells and proteins
• What is the Glomerular Filtration Rate (GFR) for males?

  125 ml/minute
• What is the GFR for females?

  115 ml/minute
• How often is the entire plasma volume filtered?

  Approximately 65 times per day
• What can be used to estimate GFR?

  Creatinine serum levels
• Which force favors filtration?

  Glomerular capillary pressure

  
• What are the main functions of tubular function in the nephron?

  • Retaining substances required by the body
  • Removing substances that need to be eliminated
• What percentage of water is reabsorbed in the nephron?

  99%
• How much plasma is filtered daily in males?

  180 litres
• How much plasma is reabsorbed daily in males?

  178.5 litres
• How much urine is excreted daily in males?

  1.5 litres
• What are the types of tubular reabsorption?

  • Passive: No energy required
  • Active: Requires energy (ATP)

  
• What substances are reabsorbed passively?

  Water and chloride ions

  
• What substances are reabsorbed actively?

  Na+, glucose, and amino acids

  
• What is transepithelial transport?

  1. Luminal membrane of tubule epithelial cell
  2. Cytosol of tubular cell
  3. Basolateral membrane of tubular cell
  4. Interstitial fluid
  5. Capillary wall to blood plasma

  
• What is NaCl commonly known as?

  Table salt
• How are Na+ levels regulated?

  By the kidney
• What happens when there is too much Na+ in plasma?

  Increased water retention and blood pressure
• What is the role of Na+-K+ ATPase?

  Exports Na+ across the basolateral membrane
• What percentage of total Na+ is reabsorbed in the proximal tubule?

  67%

  
• What percentage of total Na+ is reabsorbed in the Loop of Henle?

  25%
• What percentage of total Na+ is reabsorbed in the distal and collecting tubules?

  8%
• What hormone controls sodium reabsorption in distal tubules?

  Aldosterone