Renal Function and Electrolytes Flashcards
What are four general functions of the kidneys?
- removal of unwanted substances
- homeostasis
- electrolyte and acid/base balance (and water balance)
- hormonal regulation
what encloses each kidney
a fibrous capsule of connective tissue
what are the two regions of the kidney?
outer region: cortex
inner region: medulla
what is the function unit of the kidney? And what are the parts of this unit (in order of flow?)
the nephron
- glomerulus
- proximal convoluted tubule
- loop of henle
- distal convoluted tubule
- collection duct
What surrounds the glomerulus? What carries the blood in and out?
capillary tuft surrounded by the Bowman’s capsule
afferent arterioles carries the blood in
efferent arterioles carries the blood out
What factors affects the filtration of the glomerulus?
glomerular capillaries (between two arterioles) induce steep glomerular filtration
the semipermeable membrane
what is the function of the semipermeable membrane?
allows water, electrolytes, and small solutes (eg glucose, amino acids, low molecular weight proteins) to pass through the basement membrane and enter the proximal convoluted tubule
keeps large molecular weight molecules (bilirubin, lipids, and albumin) unfiltered
neg particles repelled due to basement membrane being negatively charged
1200 - 1500 mL of blood is received in the kidneys, and the glomerulus filters out 125 - 130 mL of protein-free, cell-free fluid called ______ ______
glomerular filtrate
what is the function of the proximal convoluted tubule?
returns the bulk of each valuable substance (in the glomerular filtrate) back into blood circulation
what are the reabsorbed substances (from the proximal convoluted tubule?)
75% of water, 100% glucose, Na+, Cl-, amino acids, vitamins, proteins, ect
What happens when the concentration of a filtered substance exceeds capacity? What is this called? What is this used for?
the substance is excreted into the urine (when it exceeds capacity). This is called the renal threshold.
Renal threshold assess tubular function and non-renal disease states
what is the loop of henle’s function?
it maintains osmolality that develops in the medulla by facilitating the reabsorption of water, sodium, and chloride
what are the two parts of the loop of henle? What is the downwards flow and upwards flow through these two limbs called, and what are the functions of the two parts?
Descending limb: permeable to water but not to Na+ and Cl-, so urine is more concentrated in this section
Ascending limb: sodium and chloride actively and passively reabsorbed (into the medullary interstitial fluid) while water is not passed, so and the urine becomes hyperosmotic (dilute)
Concurrent flow is the flow between the two limbs
what is the function of the distal convoluted tubule since most of the filtration steps have nearly been completed by the proximal tubule and loop of henle?
the DCT only has to make small adjustments to achieve electrolyte and acid-base balance homeostasis
what are the two hormones that control distal convoluted tubule function, and what do they each do?
Argenine vasopressin (also called ADH: antidiuretic hormone) stimulated when blood volume DECREASES, so it allows for water reabsorption in the DCT
Aldosterone: made by the adrenal cortex under renin influence and secreted when blood flow is low.
- Stimulates sodium reabsorption into the DCT
- Stimulates K+ and H+ ion secretion
the collecting duct is the final site for either _______ or ________ urine. ADH (AVP) and aldosterone act on this duct to control reabsorption of what two things? What additional two things are reabsorbed here?
concentrating or diluting
water and sodium
chloride and urea
what are nonprotein nitrate compounds? What are the three that the kidneys need to excrete?
they’re waste products made as a result of degradation/metabolism of nucleic acids, amino acids, and proteins
need to get rid of
- urea
- creatinine
- uric acid
Urea is the nonprotein nitrogen compound found in _______ concentration in the blood. How is it formed?
it’s found in highest concentration in the blood (in comparison to the rest of the NPN compounds)
it’s made in the liver from amino groups and free ammonia (which is toxic) during protein catabolism
how is creatinine formed?
Creatine kinase adds a phosphate to creatine to make phosphocreatine. Phosphocreatine then takes that phosphate and adds it to ADP to make ATP (energy for muscles). In doing this, phosphocreatine is turned into creatinine.
Uric acid is a waste product of _______ metabolism.
purine metabolism
- adenine and guanine
intracellular fluid account for about what ___ of fluid, which extracellular accounts for the other ____. Normal plasma is about ____ water?
2/3
1/3
93%
AVP (ADH) from the posterior pituitary is stimulated by what two things? What is the urine concentration result of this?
stimulated when there’s
- increased plasma osmolality
- decreased intravascular volume
urine is more concentrated due to water now permeable in the distal convoluted tubule. (AVP makes the DCT more permeable to water)
what happens with the renal tubules when there is an excess and deficit of water in the body?
excess water: renal tubules reabsorb water only at their minimal rate. Dilute urine formed.
dehydration (water deficit): renal tubules reabsorb water at their maximal rate, so not only is the urine concentrated, but there isn’t much of it either.
water excess will increase ______ and lower _____, which lowers ____ and _____ response
increase thirst and lower osmolality, which lowers AVP and thirst response
what happens if you have water excess but no/lower AVP?
water is not reabsorbed, so this leads to increased excretion (hypoosmolality)
what happens when there’s water deficiency? What disease has a deficiency in AVP?
increased osmolality (less water with more sodium and glucose) leads to increased AVP secretion (and thirst activation)
diabetes insipidus has a deficiency in AVP
when the kidney senses a drop in plasma volume/blood pressure, what things happen to fix this?
drop in plasma volume/blood pressure leads to
- stimulation production of renin
- which stimulates the production of angiotensinogen from the liver.
- Then angiotensin-converting enzyme (ACE) from the lung stimulates the conversion of angiotensin I to angiotensin II.
- Angiotensin II stimulates the release of aldosterone from the kidney adrenal gland.
- Aldosterone stimulates the kidney tubules to reabsorb salt and water, and excrete potassium
- The net result of this is water retention (so therefore increase plasma volume/blood pressure)
what are five analytic techniques used to assess electrolyte concentration?
ISE, volumetric assay, co-oximetry, dye-binding assay, and UV absorption
what is the principle of ISE and what electrolytes is it used for?
determines the activity of ions in aqueous solution by measuring the electrical potential
- sodium
- potassium
- chloride
- calcium
what is the principle of colorimetric assay and what electrolytes is it used for?
use of a spectrophotometer to determine concentration of a chemical compound in a solution by measuring spectral absorbance of said compound at a particular wavelength
- chloride
- magnesium
what is the principle of co-oximetry and what electrolytes is it used for?
measures the oxygen carrying state of Hgb in blood and also the different kinds of hemoglobin (O2Hb, HHB, COHb, and MetHb)
- bicarbonate
what is the principle of dye binding assay and what electrolytes is it used for?
certain strongly ionic dyes (eg amino black) form insoluble complexes with proteins at low pH
- magnesium
- calcium
what is the principle of UV absorption, and what electrolytes is it used for?
based on protein absorbing UV light at the wavelength of 280 nm due to the presence of aromatic amino acids
- phosphate
creatinine clearance relates _____ creatinine concentration with _____ creatinine concentration excreted during ____ hrs
serum
urine
24
what is the equation for creatinine clearance?
CC in mL/min = (UV / P) x (1.73 / A)
where U = creatinine in urine
V = volume or urine in 24 hours (measured in minutes, so 1440 minutes)
P = creatinine in plasma
1.73 = the average surface body area
A = body surface area in sq meters
estimated glomerular filtration rate is more ______ than creatinine clearance. What is the serum marker for eGFR? What are two reasons we like this test better than CC?
eGFR is more sensitive than creatinine clearance. Cystatin C is the marker for eGFR, a low molecular weight protein made by most body tissues and not affected by gender/age makes eGFR a less biased test.
Cystatin C levels rise quicker than creatinine in acute kidney injury
what are three glomerular diseases?
Acute glomerulonephritis
Chronic glomerulonephritis
Nephrotic Syndrome
what are four symptoms of acute glomerulonephritis and some lab tests indicating it?
symptoms: inflammation, lesion, hematuria, proteinuria
lab tests: DECREASED eGFR, anemia, INCREASED BUN and creatinine, oliguria, Na+/water retention, and CHF
what are four causes of acute glomerulonephritis?
immune complexes, drug-induced exposure, SLE, and bacterial endocarditis
what is the reason for chronic glomerulonephritis? What does proteinuria and hematuria look like in this disease?
lengthy inflammation of the glomerulus leads to scarring and loss of functioning nephrons
heavy proteinuria and possible/small amount of blood
what is the pathophysiology of nephrotic syndrome, and what are lab findings for it?
diseases that result in (direct) injury of the kidney that leads to increased permeability of the glomerular basement membrane
lab findings:
- massive proteinuria
- hypoalbuminemia (decreased oncotic pressure leads to edema)
- hyperlipidemia
- lipiduria
tubular defects occur in the ___________ of all renal diseases as GFR ______. You will see _____ filtration rate in these diseases.
tubular defects occur in the progression of all renal diseases as GFR falls. You will see decreased filtration rate (and this leads to reduced concentration.
renal tubular acidosis is caused by a decrease in ______. Decreased reabsorption in the ________ tubules leads to abnormally ____ serum for what four things?
decrease in bicarbonate
decreased reabsorption in the proximal* tubules leads to abnormally low serum:
1. phosphorus
2. uric acid
3. glucose
4. amino acids
what are some reasons/causes for tubular diseases?
radiation, toxicity, renal transplant rejection, viral/fungal/bacterial infections, and some medications
renal obstructions gradually raise the __________ pressure until what part of the kidneys necroses and ______ renal failure begins.
raise the intratubular pressure until the nephrons necroses and chronic renal failure begins
what three predisposing conditions can lead to renal obstructions?
neoplasms, acquired disease, congenital deformities
where is the problem in the body for pre, intrinsic, and post renal acute kidney failure? (name causes for each if you want.) What would be the treatment for AKF?
pre renal: defect in blood supply before it reaches the kidney
- decreased bp or cardiac output
- septicemia
intrinsic: defect in kidney
- glomerulonephritis, interstitial nephritis, pyelonephritis
post-renal: defect in UT after the urine leaves kidney
- renal calculi and tumors
treat via dialysis
what are the 7 different stages of kidney failure?
- kidney damage with normal or increased GFR
- kidney damage with normal or decreased GFR
- moderately decreased GFR
- severely decreased GFR
- kidney failure
- end-stage renal disease (chronic dialysis)
- kidney transplant
urea can lead to
liver encephalopathy
uremia is an increase in _______
all waste products
what is the anion gap, what is the formula, and what is the rr?
difference between cations and anions
Na+ - (Cl- + HCO3-)
RR: 4 - 12 mmol/L
increased anion gap due to? What about decreased anion gap?
increased: decreased unmeasured cations, increased unmeasured anions, hypocalcemia/magnesemia, keto/lactic acidosis, hyPERphosphatemia
decreased: increased unmeasured cations, decreased unmeasured anions, hypercalcemia/magnesemia, hypophosphatemia or hypoalbuminemia
