2- Glomerulus, Clearance, Regulation Ca and PO4

Question 1

Function of the Kidney

Answer 1

Regulation of ions
Excretion of waste
Endocrine: EPO, renin, prostaglandins
Metabolism: active forms of vit D, catabolism of insulin, PTH

Question 2

What is almost 100% recovered

Answer 2

Water
Sodium
Chloride
Bicarbonate
Glucose
Amino acids

Question 3

What substances are actively secreted

Answer 3

H+

Question 4

How much blood is filtered each day

Answer 4

180L/day

Question 5

How much urine is produced each day

Answer 5

1.5L

Question 6

Where is the glomerulus found

Answer 6

Cortex only

Question 7

What is the filtration fraction

Answer 7

GFR/Renal plasma flow

Question 8

How much of arriving blood exits unfiltered

Answer 8

80%

Question 9

What are the two types of nephron

Answer 9

Cortical

Juxtamedullary

Question 10

What is normal GFR

Answer 10

90-120 mL/min/1.73m2

Question 11

How is the end product of filtration different from plasma

Answer 11

No large proteins and cells (RBC)

Question 12

How do podocytes keep proteins out

Answer 12

Negatively charged so repel the neg charged proteins

Question 13

What allows filtrate to pass through

Answer 13

Fenestrations

Question 14

What pressures work in bowmans capsule

Answer 14

Hydrostatic of capillary
Hydrostatic of capsule
Oncotic of capillary and tubular lumen

Question 15

Regulation of renal blood flow and GFR

Answer 15

Myogenic and tubuloglomerular feedback mechanism

Question 16

Myogenic regulation

Answer 16

Arterial smooth muscle responds to increases and decreases in vascular wall tension
Rapid
Property of predominantly the preglomerular resistance vessels (afferent)
i.e to increase GFR constrict efferent or dilate afferent
to decrease GFR constrict afferent or dilate efferent

Question 17

Tubuloglomerular feedback with high tubular flow

Answer 17

NaCl conc at macula densa linked with renal arteriolar resistance
The higher the flow of filtrate the higher Na conc
Increased NaCl = vasoconstriction of smooth muscle in afferent to reduce renal plasma flow to reduce GFR

Question 18

Tubuloglomerular feedback with low BP

Answer 18

Release of prostaglandins reduce constriction of afferent arteriole
Renin released by juxtaglomerular cells in response to
1. sympathetic nerve stimulation
2. decrease stretch of afferent
3. macula densa signals in response to low NaCl
= RAAS

Question 19

Where does RAAS mainly work

Answer 19

Constrict efferent arterioles = increase GFR

Question 20

Issue with people on NSAIDs and ACEI

Answer 20

Inhibit prostaglandins and RAAS

Question 21

What is the equation for excretion

Answer 21

filtration-reabsorption+secretion

Question 22

What could cause a decreased GFR

Answer 22

Decrease number of nephrons

Question 23

What is renal clearance

Answer 23

Volume of plasma cleared of substance in a unit of time

Measure of kidney’s ability to remove substance and excrete it

Question 24

What is the clearance equation

Answer 24

C = conc of substance in urine (mg.mL) x urine flow rate (mL/min) / conc of substance in plasma

Question 25

What unit is clearance measure in

Answer 25

mL/min

Question 26

Where is most Ca stored and how is it stored

Answer 26

Calcium phosphate in the bones

Question 27

What is the difference between diffusible and non diffusible Ca

Answer 27

Diffusible: free ionised Ca, used for cellular processes | Non diffusible: bound to negatively charged proteins

Question 28

Where is most Ca reabsorbed

Answer 28

65% PCT Solvent drag Transcellular

Question 29

What happens in TAL to Ca

Answer 29

25% reabsorbed 50% trancellularly through Na/K/2Cl- then Na pumped out so lumen becomes positive so Ca repelled = moves between cells (Paracellularly)

Question 30

What is phosphate essential for and where is most of it found

Answer 30

Structure of bones and teeth | 80% bones, 20% interstitial fluid

Question 31

Where is PO4 reabsorbed mainly

Answer 31

PCT

Question 32

How is PO4 reabsorbed

Answer 32

2Na for every PO4

Question 33

What causes itching

Answer 33

Increased PO4

Question 34

What is the relationship between Ca and PO4

Answer 34

They precipitate to form insoluble calcium phosphate So if one increases the other is removed Inversely proportional

Question 35

What is released in response to low Ca

Answer 35

PTH

Question 36

What are the effects of PTH

Answer 36

Decrease PO4 reabsorb in PCT Increase in active Vit D Increase Ca reabsorb in DCT Increase bone reabsorb All = increase plasma Ca

Question 37

What does low Ca lead to

Answer 37

Increase in neuromuscular excitability = tetany and convulsions, cramps and arrhythmias

Question 38

Causes of low Ca

Answer 38

Hyperphosphatasemia and low levels of active Vit D Rickets and osteomalacia - low vit D Tissue injury- cells die and release PO4 Alkalosis- reduced H to bind to protein so more Ca can bind = reduced free Ca

Question 39

Treatment of low Ca

Answer 39

Oral or IV Ca Alfacalcidol Vit D analogue

Question 40

What does high Ca cause

Answer 40

``` Less excitable Slow reflexes Weakness and constipation Polyuria Bone pain and fractures Stones Groans Moans ```

Question 41

Causes of high Ca

Answer 41

``` Hyperparathyroidism Acidosis- release of Ca from protein Too much vit D Bone destruction- malignancy Granulomatous disease Drugs ```

Question 42

Treatment of high Ca

Answer 42

Treat underlying cause Rehydrate Bisphosphonates

Question 43

Causes of low PO4

Answer 43

Excessive loss Hyperparathyroidism- increase Ca so decrease PO4 Reduced GI absorption - alcohol or antacids Reduced intake Refeeding- move in to allow glycolysis DKA- insulin given- big movement in to cell Resp alkalosis- decrease CO2- shift intracellular- increase Ph cell stimulates glycolysis = lots of PO4 needed in cell

Question 44

How does DKA Resp alkalosis Refeeding cause low PO4

Answer 44

Refeeding - move in to allow glycolysis DKA- insulin given- big movement in to cell Resp alkalosis- decrease CO2- shift intracellular- increase Ph cell stimulates glycolysis = lots of PO4 needed in cell

Question 45

Signs of low PO4

Answer 45

Stones, mones, bones, groans, psychiatric overtones

Question 46

Treatment of low PO4

Answer 46

Oral or IV PO4 | Gradual refeeding

Question 47

Causes of high PO4

Answer 47

CKD - low GFR Pseudohypoparathyroidism- kidneys don't respond to PTH = low Ca so high PO4 Respiratory acidosis- decrease Ph = inhibits glycolysis DKA- PO4 not taken out of blood- risk of low when insulin given

Question 48

Symptoms of high PO4

Answer 48

``` Only with severe Spontaneous firing of neurons Tetany Involuntary contraction of muscles Calcium phosphate crystals- stones ```

Question 49

Treat high PO4

Answer 49

Phosphate binders Low dietary intake Forced diuresis