Kidneys

• What are the two main roles of the kidneys?

  Osmoregulation and excretion
• How do kidneys maintain water potential in the blood?

  By removing or retaining excess water
• What nitrogenous waste do kidneys remove from the blood?

  Urea from excess protein
• What substances do kidneys reabsorb?

  Amino acids, salts, and glucose
• How is the amount of water in urine adjusted?

  To maintain the water potential of blood
• What is the cortex of the kidney responsible for?

  Filtering the blood
• What connects the collecting ducts to the ureter?

  Renal pelvis
• What is contained in the medulla of the kidney?

  Tubes carrying filtered waste to the pelvis
• What is a nephron?

  A kidney cell
• How many nephrons are approximately in one kidney?

  About 1 million
• Where does ultrafiltration occur in the nephron?

  In the glomerulus
• What is the function of the ureter?

  Transports urine to the bladder
• What happens to large substances during ultrafiltration?

  They cannot fit through the filtration membrane
• What are podocytes?

  Specialized epithelial cells in Bowman's capsule
• What substances can fit through the filtration membrane?

  Glucose, amino acids, hormones, urea, water, ions
• What is the role of pedicels in podocytes?

  To increase surface area for filtration
• What is osmoregulation?

  The control of water potential in the blood
• What are the parts of a nephron in order?

  Bowman's capsule, proximal tubule, descending limb, Loop of Henle, ascending limb, distal tubule, collecting duct
• What does the Loop of Henle do?

  Creates a low water potential in the medulla
• What happens to salts in the Loop of Henle?

  They are transferred from ascending to descending limb
• How does the descending limb of the Loop of Henle affect filtrate concentration?

  Filtrate becomes more concentrated as it loses water
• What triggers the release of ADH?

  Low water potential detected by osmoreceptors
• What is the effect of ADH on the collecting ducts?

  Makes them more permeable to water
• What happens when there is too much water in the blood?

  Less ADH is released, urine volume increases
• What are the short-term effects of sodium deficiency?

  Disorientation, confusion, muscle cramps, nausea
• What are the long-term effects of sodium deficiency?

  Severe organ damage and strokes
• How does ADH facilitate water transport in cells?

  By inserting aquaporins into cell membranes
• What happens with more ADH in the collecting duct cells?

  More aquaporins are inserted, increasing water reabsorption
• What is the result of less ADH in the collecting duct cells?

  Less water is reabsorbed, producing dilute urine