selective reabsorption

• Selective reabsorption takes place as....


  the glomerular filtrate flows along the PCT, through the loop of Henle, and along the DCT
• PCT=


  proximal convoluted tubule
• DCT=


  distal convoluted tubule
• What do useful substances do


  leave the tubules of the nephrons and enter the capillary network that is wrapped around them
• What does the EPITHELIUM of the wall of the PCT have?


  Microvilli:

  • provide large surface area for the reabsorption of useful materials from the glomerular filtrate (in the tubules) INTO the blood (in the capillaries)
• what happens to useful solutes


  reabsorbed along the PCT by active transport and facilitated diffusion
• example of a useful solute


  glucose
• What does water enter the body by


  osmosis
• WHY does water enter the BODY BY OSMOSIS


  Because the water potential of the blood is LOWER than that of the FILTRATE

  • water is reabsorbed from the PCT , Loop of Henle, DCT and collecting duct
• What is water reabsorbed from


  the PCT , loop of Henle, DCT, collecting duct
• What is the filtrate that remains


  urine

  • passes along the ureter to the bladder
• What is urine usually made up of

  • water and dissolved salts
  • urea
  • other substances eg hormones, excess vitamins
• What does urine NOT usually contain

  • proteins and blood cells
  • glucose
• WHY does urine not usually contain proteins and blood cells


  they are too big to be filtered out of the blood
• WHY does urine not usually contain glucose


  glucose is actively transported back into the blood
• What does the volume of urine vary depending on


  how much you have drunk
• What does water potential describe


  The tendency of water to move from one area to another