Renal

Question 1

What direction does Na travel in the Na/K Pump in renal tubule cells and where is it

Answer 1

Basolateral membrane

3 Na OUT
2 K In

3Nout 2Kin

Question 2

Where is ACE produced

Answer 2

Lungs (endothelial cells)

Question 3

Paracellular transport - where does it occur in renal tubular cells? Is it diffusion vs active?

Answer 3

Paracellular transport occurs through both tight junctions and intercellular spaces in renal tubular cells

Via diffusion (not active process through primary active processes set up the gradient molecules can go down - Paracellular transport is driven by osmotic, concentration and electrical gradients.)

Question 4

Ficks law of diffusion

Answer 4

Rate of diffusion ∝ (Surface area × Concentration difference) / Membrane thickness

Question 5

Grahams law of diffusion

Answer 5

Graham’s law states that the rate of diffusion across a membrane is inversely proportional to the square root of the molecular weight of the substance

In simpler terms, lighter gases diffuse faster than heavier gases

Question 6

If a molecule is uncharged, does that make it more easily able to diffuse across a human cell membrane

Answer 6

YES

The cell membrane is more soluble for example, to NH3 than NH4+.
Uncharged weak acids or bases diffuse more readily

Question 7

Kidneys are involved in what processes? Total of 9

Answer 7

1. Excretions of waste products
2. Acid/base regulation
3. Regulation of water balance/electrolyte balance and osmolality
4. regulation of arterial BP
5. EPO
6. Vit D hydroxylation to calcitriol (1,25 di-hydroxy-cholecalciferol)
7. Secretion, metabolism and excretion of hormones
8. Gluconeogenisis
9. Prostaglandin secretion

Question 8

Na/K pump in renal tubular cells establish what electrochemical gradient

Answer 8

Net -ve intracellularly

Question 9

What is the difference between osmolality and osmolarity and why is it possible to use them interchangeably when

Answer 9

osmoLARity (LARPing in the park - which has a pond)
Number of osmotically active molecules per litre of solution

osmoLALity - number of osmotically actively molecules per kg of solvent

In the body the solvent is water so 1kg = 1L so osmolality and osmlarity is essentially the same

Question 10

What is a characteristic of glucose reabsorption in the renal tubules?

Answer 10

It has a renal tubular transport maximum. In health, glucose does not appear in the urine, as the renal tubules are capable of absorbing the entire filtered load. The starting point for glucose reabsorption involves primary active transport as described before.

Glucose reabsorption occurs by co-transport with sodium into the tubular cell, again utilising the gradient produced by the Na+/K+ ATPase pump. Glucose then diffuses into the peritubular interstitium.

If the plasma concentration rises above the renal threshold (11 mmol/L), the tubular transport maximum is reached (380 mg/min or 21 mmol/L/min).

The co-transporter mechanism becomes saturated. This means that no reabsorption can occur and glucose will appear in the urine.

Question 11

Answer 11

Question 12

Answer 12

Question 13

Answer 13

Question 14

What is a specific feature of glucose reabsorbtion in renal tubules and draw a graph of this. What is the tubular transport maximum for glucose

Answer 14

380mg/min

Question 15

What channel (and where) does furosemide act on

Answer 15

NKCC co-transporter
Thick ascending limb of the loop of Henle

Question 16

What proportion of cardiac OP do the kidneys receive? What part of the kidneys receive the majority of the blood supply?

Answer 16

20-25%

Of this the cortex receives 90% (medulla 10%)

Question 17

What is the total daily volume of filtrate produced a day

Answer 17

180L

125mls/min

Question 18

Blood supply in the kidneys

Answer 18

Aorta -> renal arteries -> segmental-> interlobal arteries -> arcuate -> afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries -> vasa recta -> veins

Question 19

What kind of nephron is more suseptible to hypoxia

Answer 19

medullary

Question 20

4 methods of autoregulation in kidnet

Answer 20

1. Prostaglandins
2. Angiotensin 2
3. Sympathetic drive
4. Tubuloglomerular feedback

Question 21

What are the function of podocytes

Answer 21

Lay down BM (T4 collagen)

Question 22

What factors effect filtration of molecules at the kidney and what size is not filtered/is freely filtered?

Answer 22

Molecular size
Charge

> 70 kDA - not filtered
<7kDA - freely filterers

Question 23

What role do mesangial cells have at the glomerulus?

Answer 23

Structural, phagocytic

Question 24

Renin is released from where?

Answer 24

juxtaglomerular cells located in the wall of the afferent arteriole

Question 25

Reabsoprtion of proteins from renal tubule

Answer 25

30g/day In health, large molecules do not pass through the glomerular membrane. Any protein molecules that do are taken up by pinocytosis at the luminal membrane

Question 26

What fluid compartments can be directly measured?

Answer 26

Total body water can be measured using heavy water (deuterium), which is freely distributed. Plasma volume can be measured by labelling albumin with a radioactive isotope or using a dye called Evans blue. They remain in the plasma and do not diffuse into erythrocytes. Total erythrocyte volume can be measured using radiolabelled (Cr-51) red blood cells. ECF volume can be measured using inulin as the tracer as it is freely distributed to the interstitial and plasma volumes.

Question 27

Which fluid compartment can be indirrectly measured?

Answer 27

Fluid compartments indirectly measured: Total blood volume can be calculated with knowledge of the haematocrit and the total circulating red cell volume. Intracellular fluid volume can be calculated by subtracting ECF volume from measured TBW.

Question 28

Fluid compartments directly measured:

Answer 28

1. Total body water can be measured using heavy water (deuterium), which is freely distributed. 2, Plasma volume can be measured by labelling albumin with a radioactive isotope or using a dye called Evans blue. They remain in the plasma and do not diffuse into erythrocytes. 3. Total erythrocyte volume can be measured using radiolabelled (Cr-51) red blood cells. 4. ECF volume can be measured using inulin as the tracer as it is freely distributed to the interstitial and plasma volumes.

Question 29

How much fluid is filtered by the kidneys every day

Answer 29

180L