Structure and function of the kidney II

Question 1

What are the 6 subdivisons of kidney function?

Answer 1

Regulation of extracellular fluid volume and blood pressure, regulation of blood osmolarity, maintenance of ion balance, homeostatic regulation of plasma pH, excretion of metabolic and other wastes and the production of hormones.

Question 2

What is the average osmolarity of the blood?

Answer 2

300mOsM.

Question 3

What is the plasma pH range?

Answer 3

7.38-7.42.

Question 4

What are some of the metabolic and wastes the kidney excretes?

Answer 4

Creatinine, urea, urobilinogen, hormones, drugs.

Question 5

What are some of the hormones the kidney produces?

Answer 5

Erythropoetin, 1,23-dihydroxyvitamin D3.

Question 6

What is the principle of mass balance?

Answer 6

Mass balance is the existing body load plus the intake or metabolic product minus the excretion or metabolic removal.

Question 7

What is the kidneys primary function?

Answer 7

Maintenance of fluid/electrolyte balance and not the removal of wastes.

Question 8

Why is homeostasis of fluid and electrolyte balance so important?

Answer 8

There are serious medical consequences which are much greater than the accumulation of metabolic wastes at a similar level.

Question 9

What is a hypotonic cell state?

Answer 9

There is too much liquid in a cell and it swells.

Question 10

What is a hypertonic cell?

Answer 10

There is too little water and the cell shrinks.

Question 11

What is an isotonic cell?

Answer 11

When there the correct amount of water and the cell does not change.

Question 12

What is the normal osmolarity of extracellular fluid?

Answer 12

285-300mosm.

Question 13

How long does it take the body to equilibrate after drinking a glass of water?

Answer 13

Around 30 minutes.

Question 14

What is the effect of adding isotonic NaCl to the body?

Answer 14

There is an increase in extracellular fluid but no effect on intracellular fluid.

Question 15

What is the effect of adding water to the body?

Answer 15

Osmolarity is reduced in the intracellular and extracellular fluid and an increased volume.

Question 16

What is the effect of adding pure NaCl to the body?

Answer 16

There is an increase in extracellular fluid and a decrease in intracellular fluid. The osmolarity is the same.

Question 17

What does sodium regulation depend on?

Answer 17

The balance between sodium being filtered and reabsorbed.

Question 18

What receptors in the body detect changes in sodium concentration?

Answer 18

Baroreceptors and osmoreceptors in the hypothalamus. They detect the levels indirectly - they detect changes in blood volume.

Question 19

What can a lack of sodium cause?

Answer 19

Hypotremia - brain damage, thyroid cancer and pneumonia.

Question 20

What can an excess of sodium cause?

Answer 20

Hypernatremia - Fevers, vomiting, diarrhea, weakness and swelling.

Question 21

What can an excess of potassium cause?

Answer 21

Hyperkalemia - vomiting, sweating and diarrhea.

Question 22

What can a lack of potassium cause?

Answer 22

Hypokalemia - excessive urination, kidney failure and cardiac problems.

Question 23

What can an excess of calcium cause?

Answer 23

Hypercalcemia - depression, kidney stones and abdominal pain.

Question 24

What can a lack of calcium cause?

Answer 24

Hypocalcemia - muscle cramps, weakness and cardiac problems.

Question 25

What can a lack of magnesium cause?

Answer 25

Hypomagnesmia - inability of intestines to absorb and confusion.

Question 26

What can an excess of magnesium cause?

Answer 26

Hypermagnesmia - adrenal insufficiency, diabetic ketocidosis.

Question 27

What factors do the kidneys monitor in order to regulate urine volume, osmolarity and acidity?

Answer 27

The cortico-medullary osmotic gradient, regional differences in the permeability of the nephron and collecting duct, regional differences in the seletive reabsorption and secretion of solutes in the nephron and collecting duct and the arrangement and proximity of the peritubular capillaries and vasa recta.

Question 28

What can occur in the proximal convoluted tubule?

Answer 28

Reabsorption and secretion from the peritubular capillaries.

Question 29

What is the basolateral membrane?

Answer 29

The membrane adjacent to interstitial fluid.

Question 30

What is the apical membrane?

Answer 30

The membrane adjacent to tubular fluid.

Question 31

How does tubular membrane transport occur?

Answer 31

The filtrate from the tubes moves into the tubular cell along a concentration gradient, but needs facilitated or carrier systems to cross the basolateral membrane.

Question 32

What is the driving force for reabsorption of water and other solutes in the nephron?

Answer 32

The electrochemical Na+ gradient that is generated by the basolateral Na+/K+ ATPase.

Question 33

What adaptations do tubule cells have for reabsorption?

Answer 33

Villi.

Question 34

What is the function of the sodium-potassium pump in the tubule cell?

Answer 34

It pumps sodium (using ATP) out of the cell to increase the concentration of sodium in the interstitial fluid that can diffuse into the peritubular capillary to create a gradient for sodium to be reabsorbed across the cell.

Question 35

What is the difference between the ascending and descending loop of Henle?

Answer 35

The descending is water permeable and the ascending is not water permeable.

Question 36

Where is the water most concentrated in the nephron?

Answer 36

At the beginning of the ascending limb.

Question 37

What is the function of the collecting duct?

Answer 37

Aquaporins can be inserted into the membrane depending on the water levels required in the body.

Question 38

What is the Na+/H+ antiporter?

Answer 38

It pumps protons out of the tubule cell in exchange for sodium. This is secondary active transport.

Question 39

How is glucose taken up into the epithelial cell in the PCT?

Answer 39

Glucose transporters on the basolateral membrane.

Question 40

How is water reabsorbed in the PCT?

Answer 40

It follows the reabsorbed ions by osmosis.

Question 41

What happens to the water in the descending limb of the loop of Henle?

Answer 41

Due to a high solute concentration in the medulla of the kidney, water moves by osmosis from the tubule to the interstitial fluid.

Question 42

What happens in the thin segment of the ascending loop of Henle?

Answer 42

It is not permeable to water but permeable to solutes - the solutes diffuse out of the tubule and move into the more dilute interstitial fluid.

Question 43

What happens in the thick segment of the ascending loop of Henle?

Answer 43

As there are specific transporters to regulate sodium reabsorption there is active processing of sodium reabsorption. Potassium and chloride ions are also reabsorbed.