Functions of the Nephron

• Selective reabsorption

  A) Blood plasma

  B) Endothelium of capillary

  C) Basement membrane

  D) Nucleus

  E) Proximal convoluted tubule epithelial cell

  F) Proximal tubule lumen

  G) Mitochondria

  H) Luminal membrane of epithelial cell

  
• What is the advantage of numerous mitochondria?

  Provides ATP for active transport
• What is the advantage of microvilli?

  Increased surface area
• What is the advantage of the diffusion distance being 1 cell thick?


  Short diffusion pathway, makes it quicker
• What is the advantage of the basement cell being so close to the capillary?

  Maintains a concentration gradient / water potential
• What is the one product not reabsorbed?

  Urea
• Loop of Henle

  A) Capillary

  B) Descending

  C) Permeable

  D) Loop of Henle

  E) Tissues of the medulla

  F) Concentration

  G) High water potential

  H) Water potential gradient across medulla

  I) Low water potential

  J) Ascending

  K) Impermeable

  L) Distal

  M) Proximal

  N) sodium

  O) chloride

  P) water

  Q) osmosis

  
• How are sodium ions transported into the capillaries from the lumen of the PCT?

  Active transport
• What does the diffusion of Na+ ions in selective reabsorption lead to?

  The co-transportation of glucose or amino acids
• Is the ascending limb permeable or impermeable to water?


  Impermeable
• How are sodium ions removed from the ascending limb?

  Active transport
• Why are sodium ions actively transported out of the ascending limb?

  To create a low region of water potential in the medulla
• How does water move out of the descending limb?

  By osmosis
• How do sodium ions move out of the descending limb?

  Facilitated diffusion
• What happens to the water potential the further up the medulla you go?


  It increases
• What is created in the interstitial space between the ascending limb and the collecting duct?

  A gradient of water potential
• What does the gradient of water potential in the interstitial space cause?

  Water to move out the collecting duct by osmosis
• Is the collecting duct permeable or impermeable to water?


  Permeable
• What does the counter current multiplier ensure?

  There is always a water potential gradient drawing water out of the tubule
• What are the channel proteins specific to water called?

  Aqua porons
• What are aqua porons controlled by?

  Anti-diuretic hormone (ADH)