Unit 10 - Kidney & Nephron Pt 2 Flashcards
What does an increase in GFR mean?
Implies a decreased absorption of fluid and solutes.
What does a decreased GFR mean?
would result in increased reabsorption of fluid and solutes.
Where is the majority of glucose reabsorbed?
at the proximal convoluted tubules and is coupled to sodium transport.
What is the concentration of glucose in the urine?
Approx. .5mmol/L
What is glucosuria?
Where glucose appears in the urine
When does glucosuria occur?
If plasma glucose is above renal threshold for glucose or if there is defective tubular reabsorption (maximum tubular transport rate for glucose is decreased).
What is Renal Threshold for glucose and Tmglucose (maximum tubular reabsorption rate)?
10-11 mmol/L
approx. 2.08 +/- 0.5 mmol per min
What is the most common cause of glucosuria?
A plasma glucose level above the renal threshold which results in excretion of the excess glucose into the urine.
diabetes mellitus, hyperthyroidism, acromegaly, acute myocardial infarction (SNS), and malignant neoplasms of the pancreas.
Where are Amino Acids reabsorbed?
at the proximal convoluted tubules and the amount excreted into the urine is dependent on the renal threshold and tubular reabsorption
What is creatinine?
The rate of formation of creatinine is proportional to the total creatine phosphate content of muscle and is therefore a reflection of an individual’s total muscle mass. The release of creatinine is so constant that the intra-individual variation in serum creatinine is less than 5 % per day. Creatinine is filtered at the kidney glomerulus and is excreted into the urine. Very small amounts are secreted by the renal tubules.
What is Urea?
A low molecular weight molecule.
It passes into the filtrate in the glomerulous of the kidney. Approx. 40-50% of the filtered load is reabsorbed by the renal tubules. This is passive to the transport of sodium.
What is uric acid?
The end product of purine degradation is uric acid.
Urates are completely filtered at the glomerulus and tubular reabsorption and secretion occurs. Most of the filtered urate is reabsorbed by then renal tubules.
What does Renin do?
Acts in the regulation of water and electrolytes.
And does active vitamin D do?
Stimulates the absorption of calcium from the small intestine. The renal cortex contains enzymes that hydroxylate 25-hydroxycalciferol, which is synthesized by the liver, to 1,25-dihydroxcalciferolm, the biologically active hormone.
What does erythropoietin do?
A glycoprotein which is also produced by the liver. Under normal conditions, the kidney is the major source of this glycoprotein. There is continuoussecretion of erythropoietin and its daily production is a function of the pO2 (the partial pressure of oxygen) of the blood perfusing the kidney. Hypoxia is a major stimulus to erythropoietin production.
What does Prostaglandins do?
Prostaglandins (PGE) are synthesized from polyunsaturates fatty acids in the cell membranes. They are produced by every organ in the body and are different from the classical hormones in that they do not appear to act at distant sites but near the same location where they are produced (local hormones).
Prostaglandins are synthesized in the renal medulla and one of these, PGE2, is known to stimulate renin release. The vasodilator effects of prostaglandins may also play a role in the regulation of blood pressure.
What are tests of the Glomerular function?
The clearance tests are designed to assess the glomerular filtration rate. Theoretically, clearance is defined as the volume of plasma from which a measured amount of substance can be completely removed into the urine per unit of time. Clearance depends on the concentration of the substance in plasma and the rate of excretion by the kidneys.
(i) urea clearance
(ii) creatinine clearance
The creatinine clearance test is preferred because creatinine is completely filtered at the glomerulus and partially (20 %) secreted by the renal tubules; there is no reabsorption.
Urea is reabsorbed (40 - 50 %) by the renal tubules.
Renal impairment can be classified according to the creatinine clearance as follows: mild 0.83; moderate 0.25 to 0.33; severe 0.08 to 0.25; and end-stage < 0.08 mL/s.
What are tests to monitor glomerular and tubular damage?
(i) serum urea
(ii) serum creatinine
(iii) urinalysis
(iv) β2-microglobulin
(v) urine protein
(vi) serum uric acid
What are tests for tubular function?
(i) urine specific gravity & osmolality
(ii) water deprivation tests
(iii) pitressin test
(iv) PSP test
(v) free water clearance
(vi) serum and urine electrolytes
(vi) ammonium chloride test.
pre-renal failure –
Decrease in RBF (so a drop in GFR)
tubular function is still OK
Intra-renal failure –
Damage to nephrons
Often probably with filtration and reabsorption
What is Renal Failure?
Kidneys fail to remove metabolic end products from blood and cease to regulate fluid, electrolyte and pH balance of ECF
Cause may be renal disease, systemic disease, urologic defects on non-renal origins
Acute failure is abrupt and referable if caught in time.
Chronic failure is the end result of irreparable damage to the kidneys that takes place over several years
How do you detect renal failure?
Acute or Chronic
Changes in urine production
Serum and urine levels of creatinine and urea
What is acute renal failure?
Rapid decline of renal function
Blood levels of nitrogenous waste increase while electrolyte and fluid balance is impaired
Dialysis and renal replacement methods helpful
What is post renal failure?
Due to obstruction of urine outflow from the kidneys
Both ureters must be obstructed to produce failure, unless on kidney is already damaged.
What is intrinsic/intra renal failure?
Conditions that cause damage within the kidney
3 Basic phases:
Onset or initiating
maintenance - sudden decrease in GFR, edema, hypertension, pulmonary congestion
recovery - urine output increases, return to normal of BUN
What is Chronic Renal Failure?
Progressive and irreversible kidney damage
Dialysis and transplantation have increased survival
Caused by DM, hypertension, nephrosclerosis, chronic glomerulonephritis and polycystic kidney disease, long-term exposure to nephrotoxins
Symptoms only upon advanced stage disease
