Function of Kidney

• What is the functional unit of the kidney?

  The nephron
• What are the two stages of urine formation in the kidneys?

  1. Ultrafiltration
  2. Selective reabsorption
• What is formed during ultrafiltration?

  Glomerular filtrate
• What happens during the process of ultrafiltration?

  Small molecules filter into the Bowman's capsule
• What are the main substances that form glomerular filtrate?

  Amino acids, water, glucose, urea, inorganic ions
• Why do blood cells and large proteins remain in the blood during ultrafiltration?

  They are too large to pass through capillaries
• What features aid ultrafiltration in the nephron?

  • Endothelium of capillary with gaps
  • Basement membrane mesh of collagen and glycoproteins
  • Epithelium of Bowman’s capsule with podocytes
• What is the role of the afferent arteriole in the nephron?

  It brings blood into the glomerulus
• How does high blood pressure in the glomerulus affect ultrafiltration?

  It forces small molecules into the Bowman’s capsule
• What is selective reabsorption in the nephron?

  • Process of reabsorbing useful substances
  • Occurs as filtrate passes along the nephron
  • Only certain substances are reabsorbed
• Where does most reabsorption occur in the nephron?

  Proximal convoluted tubule
• What adaptations do proximal convoluted tubule epithelial cells have for reabsorption?

  Microvilli, co-transporter proteins, many mitochondria
• How do microvilli aid in reabsorption?

  • Increase surface area for absorption
  • Enhance efficiency of substance uptake
• What is the function of co-transporter proteins in the proximal convoluted tubule?

  Transport specific solutes along with sodium ions
• How do mitochondria support reabsorption in the proximal convoluted tubule?

  Provide energy for sodium-potassium pumps
• What is the role of sodium-potassium pumps in reabsorption?

  Transport sodium ions out of epithelial cells
• What are the steps of sodium and solute reabsorption in the proximal convoluted tubule?

  1. Sodium ions actively transported out of cells
  2. Sodium concentration decreases inside cells
  3. Sodium ions diffuse from filtrate into cells
  4. Co-transport with solutes (e.g., glucose)
  5. Solutes diffuse into the blood
• How does water leave the proximal convoluted tubule?

  By osmosis due to lowered water potential
• What happens to urea in the proximal convoluted tubule?

  It moves out by diffusion
• What occurs in the loop of Henle regarding sodium and chloride ions?

  • Sodium and chloride ions are pumped out
  • Ascending limb is impermeable to water
  • Creates a low water potential in the medulla
• Why does water move out of the descending limb of the loop of Henle?

  Due to low water potential in the medulla
• What is the permeability of the descending limb of the loop of Henle?

  Permeable to water, low permeability to ions
• How does the loop of Henle contribute to water reabsorption?

  • Generates steep water potential gradient
  • Maximizes water reabsorption from collecting duct
• What is the final destination of water and ions that leave the loop of Henle?

  Nearby capillaries
• Bowmans Capsule Structure:

  A) efferent arteriole

  B) bowmans capsule epithelium

  C) podocyte cell

  D) glomerular filtrate

  E) basement membrane

  F) afferent arteriole

  
• Basement Membrane:

  A) red blood cell

  B) podocyte

  C) mino acids

  D) ater

  E) lucose

  F) rea

  G) inorganic ions

  H) glomerular filtrate

  I) pore

  J) blood plasma

  
• Basement Membrane:

  A) blood plasma

  B) endothelium

  C) proximal convoluted tubule epithelial cell

  D) basement membrane

  E) nucleus

  F) proximal tubule lumen

  G) mitochondria

  H) ATP

  I) ADP + Pi

  J) K+

  K) Glucose and Amino acids

  L) Na+

  M) Glucose and Amino acids

  N) luminal Membrane

  O) Basal Membrane