Physiological correlates of renal disease I Flashcards
what % of CO do the kidneys receive?
20%
how often is the entire blood supply filtered through the kidneys?
30 minutes
what are the major functions of the kidney?
- excretion
- body fluid / electrolyte balance
- elaboration of endocrine hormones
- gluconeogenesis
what three layers make up the glomerular membrane?
- endothelium of capillary
- basement membrane
- podocytes (epithelial cells)
the high filtration rate across the glomerular capillary is supported by what 3 factors?
- perforation of the endothelium (fenestrae)
- meshwork of the basement membrane
- podocytes
what is the main underlying problem in nephrotic syndrome?
increased glomerular permeability to large proteins such as albumin
plasma in the glomerular capillaries must pass through which 3 structures before it becomes glomerular filtrate?
- capillary endothelium
- basement membrane
- bowman’s capsule epithelium
what impedes the movement of proteins into the glomerular filtrate?
negatively charged basement membrane
what are the two types of nephrons?
- cortical
- juxtamedullary
what are the differences between the cortical and juxtamedullary nephrons in terms of 1) glomeruli location and 2) loop length?
cortical:
- glomeruli in outer cortex
- shorter loop
juxtaglomerular:
- glomeruli deep in cortex
- longer loop
which nephrons are surrounded by peritubular capillaries?
cortical
what are the two types of capillary beds in the kidney?
- glomerular
- peritubular
the glomerular and peritubular capillaries are arranged in series and separated by what structure?
efferent arteriole
the juxtamedullary nephrons are surrounded by specialized peritubular capillaries known as what?
vasa recta
what capillary network has an essential role in the formation of concentrated urine?
vasa recta
what is the tonicity of the glomerular filtrate in comparison to the plasma?
isotonic
the GFR is determined by what two factors?
- net filtration pressure
- glomerular capillary filtration fraction coefficient
what two components / forces make up the net filtration pressure?
where does this take place?
- hydrostatic forces
- colloid osmotic forces
- takes place across glomerular membrane
what force favors filtration?
glomerular hydrostatic
what forces oppose filtration?
- glomerular colloid oncotic
- bowman’s capsule pressure
what is the effect of afferent arteriole constriction on GFR?
decreased
what is the effect of efferent arteriole constriction on GFR?
increased
what is the effect of afferent arteriole dilation on GFR?
increased
what is the effect of efferent arteriole dilation on GFR?
decreased
60-70% of sodium is reabsorbed in which part of the nephron?
PCT
why filter amino acids, oligopeptides, and glucose carboxylates if they are not going to be excreted?
- filtration is not specific enough
- filtration is based on rate (selectivity does not occur during filtration)
which substances have a fractional excretion over 1 (excreted more than filtered)?
- potassium
- protons
- organic acids and bases
- urea
- urate
definition: alkalosis
- reduction in extracellular fluid proton concentration
- kidney fails to reabsorb filtered bicarb, increasing bicarb excretion
what is responsible for the selectivity of tubular reabsorption / secretion?
- luminal membrane
- tight junctions
what are the two pathways for reabsorption of filtered fluid and solutes from the tubular lumen into the blood?
- transcellular
- paracellular (diffusion)
the transcellular pathway of reabsorption comprises which two transport types?
- primary active
- secondary active
what type of solutes are transported transcellularly?
metabolic substrates:
- glucose
- amino acids
- fatty acids
what are the pathological steps involved in nephrotic syndrome?
- glomerular injury
- proteinuria
- reduced colloid oncotic pressure
- edema
- reduced plasma volume
pathogenesis: nephrotic syndrome
- disturbance in forces that normally partition fluid into various subcompartments of extracellular fluid space
- blood volume remains contracted even though extracellular fluid volume is expanded
