4 roles of the kidney Flashcards
What are the functions of the kidney and urinary system?
- Maintenance of body fluid composition
- maintenance of BP
- secretion of erythropoietin
- conversion of vit D
- excretion of nitrogenous waste
How is GFR controlled?
Via vasoconstriction of the afferent to decrease pressure and GFR
or via vasodilation of afferent and efferent to increase net filtration pressure and GFR
What is the glomerulus?
Loop of capillaries in the Bowman’s capsule
Why are capillary endothelium more permeable?
As they have holes in them
What do podocytes do?
Produce a slit-like network where substances enter to appear in filtrate
Which is wider afferent or efferent
afferent
Describe the intrinsic mechanism to control GFR
A myogenic response and tubuglomerular feedback
Describe myogenic response
Smooth muscle cells act as stretch receptors. Increased BP causes stretch and smooth muscle cells to contract and vice versa
Describe tubuloglomerular feedback
When macula dense detects an increase in flow rate they signal to juxtaglomerular cells to contract
causes vasoconstriction of AFFERENT arterioles
What does the extrinsic mechanism to control GFR involve?
Sympathetic nervous system and hormones
Describe the SNS control of GFR
- Intense activation of SNS during haemorrhage or dehydration
- NA causes constriction of small arteries and afferent arterioles
- can lower renal blood flow to extent that it’s inadequate for normal metabolism
Describe hormonal control of GFR
When the BP is low, juxtaglomerular cells release renin which is required for production of angiotensin II
(vasoconstriction)
What is tubular reabsorption?
Movement of useful substances from renal tubule back into blood
Where does reabsorption occur?
70% in the PCT
What are the methods of transport in tubular reabsorption?
- Diffusion
- osmosis
- passive transport
- active transport
What are tubular epithelial cells held by?
Tight junctions
What happens in the paracellular pathway?
Diffusion occurs between the adjacent cells of the epithelium
What happens in the transcellular pathway?
A substance moves into epithelial cells, diffuses through cytosol and
exits across the opposite membrane
What is sodium key for?
absorption of water and other substances
Where does the filtrate go?
It leaves the bowman’s capsule to enter the PCT
Describe filtrate
Very similar composition to plasma
What is the osmolality of filtrate?
300 mOsm/kg
How is glucose reabsorbed in the PCT?
Via the sodium/ glucose cotransporter
How are amino acids reabsorbed in the PCT?
Via the sodium/ amino acid cotransporter
