Flashcards in Renal Function: glomerular filtration and renal blood flow Deck (111)
6 functions of the kidney
- excretion of metabolic waste products (urea, creatinine)
- regulation of acid-base balance (eliminate H, acids/base, conserve bicarb)
- control of arterial pressure
- secretion, metabolism, and excretion of hormones
- excretion of foreign chemicals
What are 2 markers that are routine on all serum chemistry analyses?
Urea and creatinine
- are metabolic waste products that need to be eliminated
Kidney is responsible for long term maintenance of ____
- H+ is more tightly regulated than anything else in the body
What is the precursor for angiotensin 2?
Angiotensin 2 functions as a ______
- helps maintain bp during hypovolemia and reabsorbs Na and H2O to maintain circulating volume
What 2 hormones are critical to calcium homeostasis and maintaining proper bone metabolism and density?
Vitamin D (can only be activated in the kidney) and parathyroid hormone
What organ is responsible for maintaining blood glucose?
Liver, but kidney can convert AA and precursors to glucose during prolong fasting or liver disease
What is the main reservoir of rapidly available high energy phosphate bonds in muscle?
- Cr production is proportional to muscle mass normally
- may be increased in acute muscle diseases or decreased in chronic muscle wasting
- 1-2% of muscle creatine turns over daily to creatinine
Why is creatinine an accurate estimate of glomerular filtration rate?
Cr is strictly filtered by the glomerulus with little or no secretion or reabsorption by the renal tubules
Renal damage is ____ over the life of the animal
Cumulative, nephrons don't regenerate
- Serum Cr will increase over time
Does the kidney alter it's function in response to changes in creatinine?
No, a change in Cr does not cause a change in GFR for compensation
- use serum Cr as an indicator of a changing GFR (as a result of something else)
GFR primarily responds to changes in ____
Excessive protein intake leads to ____
Greater urea production and elimination
- could be due to increased intake, or increased body protein catabolism or degradation (seen in starvation)
Must eliminate _____ as urea, or ____ will accumulate
NH2, NH3 (ammonia)
Changes in urea results in _____
Significant changes in water excretion or retention
_____ follows urea!!!
- urea is a potent osmotic particle
In excessive urea production and elimination, GFR will ______ and urine volume will _______
During dehydration, the kidney will _____
Actively reabsorb urea to retain water or reduce water excretion
____ and ____ are indicators of loss of function
BUN and Cr (are late indicators)
The kidney is the most important organ for getting rid of ____
- H ion concentration is tightly controlled (to the 0.00004 meq/L
What are the 3 mechanisms of H control?
- buffers: act in seconds
--> proteins to act as temporary H+ sink
--> weak acid anion: bicarb, phosphate, etc
- respiration: act in minutes
--> eliminates CO2, leaving water instead of carbonic acid (bicarb loss)
- kidney: slow, but most important
Every time a CO2 is excreted, a ______ ion is lost
Bicarb (1:1 ratio)
Rates at which different substances are excreted in the urine represent sum of 3 different renal processes
- glomerular filtration
- reabsorption of substances from renal tubules into the blood
- secretion of substances from blood into renal tubules
If intake of water/electrolytes exceeds excretion, the amount of that substance in the body will ____
Urine formation begins with fluid that is virtually free of ____
- most substances in plasma are freely filtered, so their concentration in the glomerular filtrate in Bowman's capsule is the same as in the plasma
What happens to a substance that is freely filtered by glomerular capillaries but is neither reabsorbed or secreted?
Excretion of all that is filtered
- excretion rate is equal to the rate at which it was filtered
- is a good estimate of GFR
- example of creatinine
What happens to a substance that is freely filtered but is partly reabsorbed from the tubules back into the blood?
Rate of urinary excretion is less than the rate of filtration at the glomerular capillaries
- typical for electrolytes (Na, Ca, K)
What happens to a substance that is freely filtered at the glomerular capillaries but is not excreted into the urine?
All the filtered substance is reabsorbed from the tubules back into the blood
- amino acids and glucose