Name

 

1. What is the name of the fatty tissue that lies around each kidney?

The adipose capsule.

 

2. About how many nephrons are there in each kidney?

One million.

 

 

3. What is the function of the nephrons?

To form urine.

 

4-5. What are the two types of nephrons and where are each located?

Cortical nephrons -  lie completely within the cortex, Juxtamedullary nephrons – lie in both the cortex and medulla

 

6. Why do the renal pyramids look striated?

Because of parallel bundles of ducts carrying urine from the nephrons.

 

7. What cell type makes up the parietal layer of the glomerular (Bowman's) capsule?

Simple squamous epithelium

 

8-10. What is another name for the apical side of the cells lining the PCT?  What is present on the apical side of the cells lining the PCT?  What is its function?

Luminal side. Microvilli.  Increases surface area for reabsorption.

 

 

11. What cell type lines the thin descending loop of Henle?

Simple squamous epithelium

 

12. What features of cells in the thick ascending loop of Henle and early DCT make this membrane highly permeable to solutes, but not water?

A glycoprotein layer and ‘tighter’ tight junctions greatly restricts the diffusion of water. The basolateral membrane contains many integral proteins for passive and active membrane transport processes, allowing permeability of solutes.

 

 

 

13. Where is the juxtaglomerular apparatus?

Where the cells of the afferent and efferent arterioles and of the thick ascending loop of Henle are in contact with each other.

 

14-15. What two cell types are found in the late DCT and cortical collecting duct?  Which are more numerous?

Principal and Intercalated cells.  Principal cells are more numerous.

 

16. What tissue type are the cells of the late DCT and cortical collecting duct?

Simple cuboidal epithelium

 

17. What cell type is found in the medullary collecting duct? 

Principal cells.

 

Early Filtrate Processing

 

18-19. What two renal processes are accomplished by the renal tubules? Briefly review each process.

(1) Reabsorption: movement of solutes and water back into the blood from the filtrate.  (2) Secretion: movement of some solutes from the blood into the filtrate.

 

20-21. Which is a more selective process: glomerular filtration or reabsorption?  Discuss.

Glomerular filtration nonselectively allows any ions and molecules which are small enough to pass from the blood into the glomerular capsule.  Reabsorption selectively "takes back" the valuable components of blood from the filtrate into the blood.

 

22-23. What are the two pathways for reabsorption? Trace the movement of a substance for each.

Transcellular & Paracellular.  In transcellular reabsorption, a chemical moves through the luminal and basolateral membranes of the tubular cells into the interstitial space and then into the peritubular capillaries. In paracellular reabsorption, the chemical moves through the tight junctions into the lateral intercellular space and then into the peritubular capillaries.

 

 

24. Why is it said that ion pump carries out primary active transport of sodium ions?

Because ATP directly provides the energy to pump the ions against their gradients.

 

 

 

25-28. a. What is the function of the Sodium/hydrogen Countertransport Molecule on the luminal membrane of the PCT?  What does it transport and in what direction?  b. Why is its activity dependent on the sodium potassium pump in the basolateral membrane?  c. Why is this called countertransport?  d. Why is this called secondary active transport?

a. Carries a sodium ion into the cell (from high to low concentration) and in exchange secretes a hydrogen ion (from low to high concentration) out of the cell into the filtrate.  b. It keeps the concentration of sodium in the cell low.  c. Because one substance (hydrogen ion) goes out of the cell while at the same time another substance (sodium ion) goes into the cell.  d. Because it depends on the sodium potassium pump (which requires ATP) keeping the concentration of sodium low in the cell for its activity.  So ATP is used to pump out the sodium, which allows the carrier to function.

29-30. a. What is the function of the Sodium Channel on the luminal membrane of the PCT?  What does it transport and in what direction?  b. Why is its activity dependent on the sodium potassium pump in the basolateral membrane?

a. Allows sodium to diffuse from high to low concentration into the cell.   b. It keeps the concentration of sodium in the cell low. 

 

 

31. What is the function of the Sodium/Glucose Cotransport Carrier Molecule on the luminal membrane of the PCT?  What does it transport and in what direction?  b. Why is its activity dependent on the sodium potassium pump in the basolateral membrane?  c. Why is this called cotransport?  d. Why is this called secondary active transport?

It allows sodium to move into the cell from high concentration to low concentration.  At the same time glucose moves into the cell often from lower to higher concentration.  b. It keeps the concentration of sodium in the cell low, allowing the sodium to diffuse from high to low concentrations.  c. Because both sodium and glucose move in the same direction at the same time.   d. Because it depends on the sodium potassium pump (which requires ATP) keeping the concentration of sodium low in the cell for its activity.  So ATP is used to pump out the sodium, which allows the carrier to function.

 

32-38. (Overview.) Fill out this chart with "permeable" or "impermeable".

 

Permeability to Water

Permeability to Na+ and Cl-  Ions

Permeability

to Glucose

Proximal Convoluted Tubule

Permeable

Permeable

Permeable

Descending Loop

of Henle

Permeable

Impermeable

         _____________

 

Ascending Loop

of Henle

Impermeable

Permeable

         _____________

 

 

 

39. What is the main factor that determines what passes through the filtration membrane?

The size of the particles

 

40. Blood can be divided into particles, based on size:  blood cells, protein, and small molecules and ions.  Which of these can freely pass through the filtration membrane?

Small molecules and ions.

 

 

41. What process drives filtration?

Glomerular filtration is bulk flow driven by the hydrostatic pressure of the blood.

 

42-43. What are the four main categories of components of the glomerular filtrate?

Organic molecules, nitrogenous waste, ions, and water.

44-45. Give two examples of organic molecules that are filtered at the glomerulus.

Glucose and amino acids

 

46-48. Give three examples of nitrogenous wastes that are filtered at the glomerulus.

Urea, uric acid, and creatinine

 

49-51. Give three examples of ions that are filtered at the glomerulus.

Sodium ions, potassium ions, and chloride ions

 

52-57. What are three forces affecting filtration at the glomerulus.  In which direction (towards the blood or towards the filtrate) does each of the forces push fluid?

(1) hydrostatic pressure within the glomerular capillaries - pushes fluid toward the filtrate   (2) back pressure from fluid within the capsule - pushes fluid toward the blood   (3) osmotic pressure within the glomerular capillaries - pushes fluid toward the blood

 

58. What increases or decreases the GFR?

Changes in hydrostatic pressure within the glomerular capillaries, back pressure from fluid within the capsule, and/or osmotic pressure within the glomerular capillaries.

 

59. What does a high osmolarity (high concentration of sodium and chloride ions) in the terminal portion of the ascending loop of Henle indicate?

When the GFR is high, filtrate moves quickly through the tubules and there is not much time for ions and other solutes to get reabsorbed back into the blood.  So the concentration of ions in the filtrate remains high.

 

60. What does a low osmolarity (low concentration of sodium and chloride ions) in the terminal portion of the ascending loop of Henle indicate?

When the GFR is low, filtrate moves slowly through the tubules and there is a lot of time for ions and other solutes to get reabsorbed back into the blood.  So the concentration of ions in the filtrate is low.

 

61. What cells produce and secrete renin?

Juxtaglomerular cells of the afferent arteriole.

 

62. When is renin released?

When filtrate osmolarity is low, when there is a low filtrate flow rate, and when the blood pressure dips below 80 mm Hg.

 

63. What is the effect of renin?

Renin activates angiotensin II which causes constriction of the efferent arteriole.