Kidney function 1 - excretion Flashcards
what are the two main processes in the Glomerlus/ PCT?
-ultrafiltration
-reabsorption
what does ultrafiltration mean?
-the filtration of plasma and substances below a certain size into the Bowmans capsule
where does ultrafiltration occur?
-the glomerulus
does ultrafiltration recognize useful products?
-it doesn’t recognize useful products
why is reabsorption necessary?
-as ultrafiltration is based purely on molecular size and not on whether or not the products are useful, it’s essential that filtered useful products are selectively reabsorbed back into the bloodstream in the nephron
what kind of pressure does blood have when entering the glomerulus?
-a high hydrostatic pressure
why does blood entering the glomerulus have a high hydrostatic pressure? (3 reasons)
-the short distance blood has to travel to get to the kidneys through the renal artery
-the fact that the afferent arteriole is wider than the efferent arteriole
-coiling of capillaries in glomerulus restricts blood flow and increases pressure
what are the 5 small components in the blood that are forced out due to the high hydrostatic pressure?
-glucose
-amino acids
-salts
-water
-urea
where are the 5 small blood components forced out to due to the high hydrostatic pressure?
-it forces these components out of the blood and into he Bowmans capsule
can larger components of the blood pass to the Bowmans capsule, why? what are these components?
-they can’t because they are too large and ultrafiltration is based purely on molecular size
-red blood cells, white blood cells and large plasma proteins
how is the process of ultrafiltration aided?
-by the structure of capillary walls and the lining of the Bowmans capsule
-both are very thin so blood can pass through easily
what type of cells make up the walls of the glomerulus? what do these walls also have and why?
-single layer of flattened endothelial cells
-the walls contain pores
what type of cells makeup the walls of the Bowmans capsule and what are their job?
-it’s lined with specialized cells known as podocytes which allow the filtered material to pass through easily
what is the extension called that separates the capillary and podocytes?
-the basement membrane
what is the job of the basement membrane?
-it is the effective filter which determines which components of the blood enter the Bowmans capsule
-it also prevents the blood cells and large plasma proteins from leaving the blood
what are the three layers that separate the blood in the capillaries and the inside of the Bowmans capsule?
-capillary endothelial cells
-podocytes
-basement membrane
how are each of the layers that separate blood in capillaries with the inside of the Bowmans capsule specialized?
-they are specialized by either being porous (capillary walls and podocytes) or through acting as a filter (basement membrane)
what are the two forces that cause ultrafiltration?
-hydrostatic pressure which forces water and small components into the Bowmans capsule
-water potential on each side of the membrane
what must the water potential be like for filtration to occur?
-the water potential within the Bowmans capsule (Bowmans filtrate) must have a more negative potential/ concentrated than blood in the glomerulus
what are the two components of water potential?
-pressure potential and solute potential
what is the hydrostatic pressure in the blood like compared to the pressure in the glomerular filtrate ?
-the hydrostatic pressure of the blood is much greater than the hydrostatic pressure created by the filtrate in the nephron
by what blood component is the solute potential represented and why?
-plasma proteins
-this is because there are plasma proteins in the glomerulus capillaries but not in the filtrate
what is the solute potential like in the filtrate compared to the blood? why is this not an issue?
-the filtrate has a less negative/ more dilute solute potential than in the blood
-although the difference opposes filtration the effect is insignificant when compared to the hydrostatic pressure
look at worked example in book of pressure equation thing
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