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Flashcards in Costanzo Renal Physiology Chapter Deck (17)
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1

What are the three hormones that kidneys secrete?

Renin
- in response to low blood volume

Erythropoietin
- in response to low hematocrit/hemoglobin

1,25 dihydroxycholecalciferol (activated vit. D)

2

What is the major structural differences between the DCT and PCT?

PCT has lots of microvilli (brush border) to increase surface area reabsorption

Differences in channels and receptors

3

Differences between superfical and juxtamedullary nephrons

Superficial:
- glomeruli are in the outer cortex
- lower GFR and less concentrated urine
- short loops of Henle which only reach outer stripe of medulla

Juxtamedullary:
- glomeruli are in the corticomedullary border
- higher GFR and more concentrated urine
- Long loops of Henle which reach the inner medulla and papilla

4

How is the blood flow/arteries set up in the renal system?

Renal artery -> interlobular arteries -> arcuate arteries -> cortical radial arteries -> afferent arterioles, efferent arterioles -> peritubular capillaries -> small veins -> renal vein

5

What is the purpose of the peritubular capillaries?

To be the primary site of exchanging solutes between the urine/loop of Henle

6

How much of total body weight does water account for?

Roughly 60%

TBW = 2/3 ICF (40% TBW) and 1/3 ECF (20% TBW)

ECF = 2/3 interstitial fluid and 1/3 plasma

“60-40-20 rule”
- 60% weight = TBW
- 40% weight = ICF
- 20% weight = ECF

7

What are the major cations and anions for the ICF?

Cations
- potassium and magnesium

Anions
- proteins
- ATP/ADP/AMP (organic phosphates)

8

What are the major cations and anions for the ECF?

Cations
- sodium

Anions
- chloride and bicarbonate

9

What is the normal percentage of TBW?

50-70%

10

What is the normal value for osmolarity of the body fluids

290mOsm/L

11

How to calculate osmoles and how to calculate new osmolarity from lost fluids

Osmolarity of a fluid x total volume of a fluid

New osmolarity = (old -new) / total volume

12

What factors affect the renal blood flow and how?

1) Sympathetic nervous system and catecholamines
- vasoconstriction of both afferent and efferent arterioles
- **affects afferent more though since it has more a1 receptors
- **causes decreases in both RBF and GFR

2) Angiotensin 2
- vasoconstriction of both afferent and effect arterioles
- **affects efferent arterioles more since it has high number of receptors
- ** causes increases in GFR in short doses and decreases in GFR in large doses
- *** always has no effect on RBF (since PGEs counter-the vasoconstriction)

3) Atrial naturetic peptide (ANP)
- dilates afferent arterioles and constricted efferent arterioles
-** increases RBF and GFR

4) prostaglandins
- vasodilation of both afferent and efferent arterioles
- ** primarily only work on countering the potential negatives of vasoconstriction seen in
Angiotensin 2

5) dopamine
- low levels = vasodilation
- increases RBF and has no effect on GFR

13

Myogenic hypothesis

States that increased arterial pressure stretches the blood vessels which causes reflex contraction of smooth muscles in blood vessel walls
- this occurs due to stretch activated calcium channels in these blood vessels

* is a theory behind auto regulation of RBF

**this attempts to keep RBF at constant levels and prevent rupture of renal arteries

14

How does venous blockage affect pressure and lymph flow?

Osmotic pressure = increases

Protien pressure (oncotic) = decreases

Lymphatic flow = increases

15

How does renal artery stenosis affect GFR and concentrations?

Would reduce GFR by a percentage

Would reduce blood flow by same percentage as GFR

Would transiently reduce creatinine secretion, but would return to normal after serum creatinine goes way up

Would increase serum creatinine by a lot

Would transiently reduce sodium secretion, but would return to normal side to auto regulation

No change in plasma sodium

16

How is phosphate excretion controlled?

By an “overflow” mechanism

Almost always phosphate filtered exceeds reabsorption levels, so the excess phosphate ions that is not reabsorbed can buffer H+ ions in the urea
- the threshold for phosphate is usually 0.8 mmol/L and is almost always exceed except in hypophosphatemia condtions

**parathyroid hormone is not required for this overflow mechanism to occur

17

In the case of GFR decreasing, what is the most sensitive molecule that increases in plasma concentration

Creatinine
- is solely dependent on GFR