3- Roles of the Kidney Flashcards
What are the functions of the Kidneys and the urinary system
Maintenance of bodily fluid composition
Maintenance of blood pressure
Maintenance of erythropoietin
Conversion of vitamin D
Excretion of nitrogenous wastes
What does vasoconstriction of the afferent arteriole fo to GFR
Decreases net filtration pressure and GFR
What does vasodilation of afferent and vasoconstriction of efferent do to net filtration and GFR
Increases net filtration pressure and GFR
What are the Intrinsic Mechanisms of the control of GFR
Myogenic response- smooth muscle cells act as stretch receptors. Increased blood pressure causes stretch and smooth muscle cells contract causing vasoconstriction of afferent arteriole.
Tubuloglomerular feedback- When cells of the macula densa detect an increase in flow rate, signal to juxtaglomerular cells to contract and this causes vasoconstriction of afferent arterioles
What are the extrinsic mechanisms that control GFR
Sympathetic innervation- intense activation of the sympathetic nervous system(dehydration), noradrenaline causes constriction of small arteries and afferent arterioles.
Hormone- When blood pressure is low, juxtaglomerular cells will release renin, which is required for the production of the vasoconstrictor angiotensin II
What is tubular reabsorption
Movement of useful substances from renal tubule back into blood.
What are the methods of transport for tubular reabsorption
Diffusion
Osmosis
Passive transport
Active transport
What is paracellular tubular reabsorption
Diffusion occurs between the adjacent cells of the epethelium
What is transcellular tubular reabsorption
A substance moves into an epithelial cell, diffuses through the cytosol, and exits across the opposite membrane.
What happens in the proximal convoluted tubule
Filtrate leaves Bowman’s capsule and enters proximal convoluted
Composition very similar to plasma (minus blood cells and larger protein molecules)
Osmolality – 300 mOsm/kg (very similar to plasma)
How are amino acids and glucose reabsorbed in the PCT
Through cotransporters and transporters
What is paracellular reabsorption in PCT
As other solutes are reabsorbed, through the proximal convoluted tubules and into the interstitial fluid, water follows by osmosis
Causes concentration of solutes that remain in the tubular lumen (e.g. K+, Ca2+, Mg2+) to increase
These solutes diffuse when their concentration in the lumen is higher than in the interstitial fluid
What happens in the loop of henle
Filtrate leaves proximal convoluted tubule and enters loop of Henle
Descending and ascending limbs have different epithelial cell types
Different permeability of each limb to water and solutes
What happens in the loop of henle ascending limb
Active transport of NaCl in the thick section of the ascending limb
The thick section of the ascending limb is impermeable to water (water remains in tubule)
Increases NaCl concentration in the medullary interstitial fluid
Contents of tubule becomes more dilute
Thin segment of the ascending limb is also permeable to Na+ and Cl-
Not permeable to water
Na+ and Cl- reabsorption increases the osmolality of the interstitial fluid of the inner medulla
What happens in the loop of henle descending limb
Wall of descending limb is permeable to water
The interstitial fluid in medulla has high osmolality
Water moves by osmosis into interstitial fluid (and vasa recta)
Additional 15% of the filtrate volume is reabsorbed
