Homeostasis & The Kidney

Question 1

What is homeostasis?

Answer 1

-The mechanism by which a constant internal environment is achieved

Question 2

What are the two functions of the kidney?

Answer 2

• Removal of nitrogenous waste from the body

- Osmoregulation (the control of the water potential of the bodys fluids)

Question 3

What is the structure of a section of the kidney?

Answer 3

• An outer cortex
• An inner medulla
• Which forms renal pyramids
• A pelvis at the centre which narrows to become the ureter

Question 4

What are the three processes that happen in the kidney’s nephrons, and where do they take place?

Answer 4

• Ultrafiltration (in the glomerulus)
• Selective reabsorption (in the proximal convoluted tubule)
• Secretion (in the distal convoluted tubule)

Question 5

What is the layer of cells surrounding capillaries in the glomerulus?

Answer 5

• Podocytes
• Have foot like processes known as pedicels
• Which have narrow spaces in between called slit pores

Question 6

What is ultrafiltration?

Answer 6

-Filtering under high pressure that separates small molecules from the blood plasma

Question 7

What does the filtrate in the Bowman’s capsule contain?

Answer 7

• Water
• Glucose
• Salts
• Urea
• Amino acids

Question 8

What are some adaptations of the proximal convoluted tubule for selective reabsorption?

Answer 8

• Increased surface area due to the amount of tubules
• Increased surface area due to microvilli
• Lots of mitochondria to produce ATP
• Tight junctions between cells to prevent reabsorbed substances seeping back into the filtrate

Question 9

How are substances reabsorbed during selective reabsorption?

Answer 9

• Most mineral ions reabsorbed by active transport
• All glucose and amino acids reabsorbed by co-transport with sodium ions
• Most water is reabsorbed by osmosis
• Some urea and some small proteins reabsorbed by diffusion

Question 10

How does selective reabsorption happen in the loop of Henlé?

Answer 10

• Chloride ions actively transported out of the filtrate in the ascending limb, creating a low water potential in the medulla
• Water is drawn out the descending limb by osmosis to create a lower water potential at the bottom of the loop
• In the collecting duct, water is reabsorbed by osmosis as the medulla has a low water potential