9/8- Review of Renal Physiology Flashcards Preview

MS2 Renal > 9/8- Review of Renal Physiology > Flashcards

Flashcards in 9/8- Review of Renal Physiology Deck (57)
1

T/F: there are a few, scattered glomeruli in the renal medulla?

False; the renal medulla = tubules + vessels (no glomeruli)

2

Describe the vasculature of the kidney?

Renal artery -> afferent arteriole -> glomerula caps -> efferent arteriole -> peritubular caps

 

Vasa recta = peritubular caps of the juxtamedullary nephrons 

3

What comprises the glomerular filtration barrier?

1. Capillary endothelial cells

2. Glomerular basement membrane

3. Glomerular epithelial cells (podocytes)

4

What are barriers to glomerular filtration?

- Size (MW under 5,500 = freely filtered)

- Charge (major determinant for MW 5.5-44K, fixed negative charges on filtration surface)

- Shape (minor determinant)

5

Names for inner tubule surface?

Luminal or apical

6

Names for outer tubule surface?

Peritubular or basolateral

7

What is reabsoprtion?

Transport of water/solutes form inside -> outside the tubule

8

What is secretion?

Transport of water/solutes form outside -> inside tubule

9

Urine volume = ?

Urine volume = filtration - reabsorption + secretion

10

What is the role of the proximal nephron (PCT or PST)?

Bulk reabsorption of water and solutes (Na, Cl, HCO3, glucose)

11

What is the role of the Loop of Henle (tDLH, tALH, TALH)?

- Moderate solute reabsorption

- Urine concentration and dilution

12

What is the role of the distal nephron (DCT, CND, collecting tubule- initial, cortical, outer/inner medullary)?

- "Fine-tune" urine composition

13

What is the distribution breakdown of water in the extracellular vs. intracellular compartment?

Extracellular ~40% (17 L)

- Blood plasma = 3 L

- Interstitial fluid = 13 L

- Transcellular fluid = 1 L

Intracellular ~ 60% (25 L)

(Total body water = 42 L)

14

Solute composition of plasma?

- Na: 142

- K: 4.4

- Ca: 1.2 (ionized)

- Mg: 0.6 (ionized)

- Cl: 102

- HCO3-: 22

- Proteins: 7 g/dL

- Glucose: 5.5 mM

pH = 7.4

Osmolality = 291

15

Volume balance: synonymous terms for intravascular volume?

- Plasma volume

- Effective circulating volume

- 1/4 of extracellular fluid (ECF) volume

These determine blood pressure

16

In what conditions will you see a dissociation between total body volume and effective circulating volume?

Some disease states:

- CHF

- Cirrhosis

- Kidney disease

17

T/F: Volume balance = water balance?

FALSE

18

Change in water balance changes what factors? Salt balance?

Change in water balance:

- Relatively BIG change in osmolarity

- Relatively SMALL change in ECF volume

Change in salt balance:

- Reflected by ECF volume

- Represents a minimal change in serum sodium (Na) osmolarity

19

Describe the renin-angiotensin-aldosterone axis (picture)

20

What triggers renin release? Inhibits?

Stimulated by:

- Hypotension

- Increased sympathetic outflow to JGA

- Renal hypoperfusion (renal baroreceptors)

- Endothelin, PGE2, PGI2

Inhibited by:

- Hormones (Angiotensin II, AVP)

- Other: high [K], nitric oxide

21

What triggers anigotensin II release?

- Increase systemic blood pressure

- Aldosterone release

- Increase sensitivity of Tubuloglomerular feedback

- Stimulate Na-H countertransport

- Stimulate AVP and thirst centers

- Efferent arteriolar vasoconstriction

22

ICF volume is a reflection of what?

Water balance/osmolarity

23

What are sensors of ICF volume?

Osmoreceptor input

24

What are effector pathways of ICF volume

- AVP (via ADH)

- Thirst

25

What solutes are excreted by tubules:

- Completely

- Partially

- Not at all

- Completely: PAH

- Partially: creatinine, Na

- Not at all: glucose, bicarbonate

26

Equation for arterial content?

(RPFa)(Px,a)

27

Equation for venous content?

(RPFv)(Px,v)

28

Equation for urine content?

(V)(Ux)

29

Equilibrium equation?

(RPFa)(Px,a) = (RPFv)(Px,v) + (V)(Ux)

Basically, arterial content = venous content + urine content

30

Equation if solute is completely extracted?

Px,v = 0,

therefore: (RPFa)(Px,a) = (V)(Ux)

and

(RPFa) = (Ux)(V)/(Px,a)

31

What is clearance?

Cx = (Ux)(V)/(Px)

32

What are characteristics of the ideal marker to estimate glomerular filtration rate? What is it?

- Freely filtered in the glomerulus

- No tubular reabsorption or secretion

- Not synthesized or metabolized

- Physiologically inert

This is Creatinine

- Endogenous product of muscle metabolism

- Easy to measure its value in the blood

- Stable rate of production

33

Is creatinine filtered? Reabsorbed? Excreted?

- Filtered

- NOT reabsorbed

- Secreted

34

What is the rate of creatinine production for males/females?

Males: 15-20 mg/kg ideal body weight

Females: 15-20 mg/kg ideal bod weight

35

Alternate markers to creatinine?

- Inulin (gold standard)

- B12

- Iothalamate

- EDTA

36

Clearance of creatinine estimates what?

The glomerular filtration rate (GFR)

37

What is normal GFR?

100-125 mL/min (adults)

- Males > females

- Declines with age

38

Does stable serum creatinine = stable kidney disease?

No

- The sCr is not a great marker also because it is maintained despite loss of GFR due to tubuloglomerulofeedback (recruitment of other gloms) and increased tubular Cr secretion 15% to 35%.

39

Results of regulation of GFR (glomerulotubular balance)?

Glomerulotubular balance:

- No change in fractional excretion/reabsorption

- High GFR -> high absolute reabsorption / excretion

- Low GFR -> low absolute reabsorption / excretion

- Prevents excessive changes in solute excretion

40

How is GFR regulate?

1. Tubuloglomerular feedback (TGF)

- Macula densa (MD) senses changes in solute delivery (MD = specialized cells near distal tubule & vascular pole)

- Results in release of vasoactive substances -> change GFR

2. Neurohormonal effects- Vasoconstriction

- Angiotensin II: Arteriolar vasoconstricton efferent > afferent

- Arginine vasopressin: Renal vasoconstriction medulla > cortex

- Sympathetic nervous system activation

- Modulators: epinephrine, endothelins, leukotrienes

41

Does anigotensin II vasoconstrict the afferent or efferent arterioles more?

Efferent > afferent

42

What is the range of urine osmolality?

30-1200 mOsm (daily solute exretion ~ 600 mOsm)

43

What is the lowest possible urine volume? Highest?

Lowest: V = 600/1200 0.5 L/day

Highest: V = 600/30 = 20 L/day

44

What is the osmolarity of the fluid entering the descending thin limb? In the medullary interstitium?

- Fluid entering tDL: 300 mOsm

- Medullary interstitium: 1200 mOsm

Established by the countercurrent multiplier system

45

What is arginine vasopressin?

Aka aldosterone or anti-diuretic hormone (ADH)

46

What is the mechanism of action of ADH? What stimulates/suppresses it?

- Insertion of water channels (aquaporins) into apical membrane in collecting ducts

- Upregulate Na/K/Cl cotransport in thick limb

- Insertion of urea transporters (UT1) into apical membrane in medullary collecting ducts

- Stimulated by hyperosmolarity

- Suppressed by hypoosmolarity

47

What are major hormones controlling phosphorus regulation?

Parathyroid hormone (PTH)

- Decreases PO4 reabsorption (increases excretion)

- Downregulates apical transporter expression 1,25-dihydroxy vitamin D

- Increases PO4 reabsorption (decreases excretion) at distal nephron

Increase PO4 excretion:

- Increase intake

- ANP

- Glucocorticoids

- Acidosis

48

Describe calcium regulation in terms of Na and other hormones?

- Increased Na reabsoprtion -> increased Ca reabsorption (and vice versa); it follows Na!

- PTH: increases Ca reabsorption in TAL, DCT, CCT

- Vitamin D: increases Ca reabsorption in distal nephron

- Loop diuretics: decrease Ca reabsorption

49

What is normal blood pH? Minimal urine pH?

- Normal blood: 7.4

- Minimal urine: 4.4

50

What is acidemia? What causes it?

Low pH of blood, caused by either:

- Respiratory acidosis (high PCO2)

- Metabolic acidosis (low HCO3)

Acidemia does NOT = acidosis (acidemia is the net pH change; acidosis is the process leading to this)

51

What is alkalemia? What causes it?

High pH of blood caused by either:

- Respiratory alkalosis (low PCO2)

- Metabolic alkalosis (high HCO3)

Alkalemia does NOT = alkalosis

52

What are the ECF buffers? Relative importance/effectiveness?

1. Bicarbonate (CO2/HCO3)

2. Proteins

3. Phosphate (H2PO4/HPO4)

53

What are the relevant equations for CO2/HCO3 buffer pair?

pKa of the bicarbonate buffer system = 6.1

pH = 6.1 + log (HCO3)/(CO2)

pH = 6.1 + log (HCO3)/(PCO2 x 0.03)

54

Why is bicarbonate buffer system (pKa = 6.1) better than phosphate (pKa = 6.8)?

- [HCO3] >> [total phosphates]

- Open system (respiratory adjustment of CO2 and renal adjustment of HCO3)

55

How does the kidney respond to respiratory processes? (speed, HCO3 handling...)

- Slow (hours or days)

- Reclamation of filtered HCO3

- Increased titratable acid excretion

- Very increased ammoniagenesis

- H secretion = HCO3 reabsorption

56

How does the kidney respond to metabolic alkalosis?

Suppression of proximal H+ secretion

- Inhibit basolateral Cl-HCO3 exchange

- Increase HCO3 paracellular backleak

Suppression of ammoniagenesis

Inhibit H+ secretion in Cortical Collecting Duct

- Decrease alpha-type intercalated cells (H+ secretion)

- Increase beta type intercalated cells (HCO3 secretion)

57

Correction of metabolic alkalosis is very sensitive to ________. Elaborate

Correction of metabolic alkalosis is very sensitive to ECF volume status

- Volume depletion limits ability to correct alkalosis

1. Decreased GFR = decreased filtered load HCO3

2. Decreased Na delivery = decreased Na reabsorption (Na-H exchange)

3. Decreased ECF volume = Increased aldosterone (Increased H+ secretion)