Function & anatomy Flashcards
What is the function of the kidneys?
- Regulation of fluid & electrolytes
- Excretion of waste
- Acid-base balance
- Long-term regulation of blood volume
- Production (Vit D & EPO)
What is the gross drainage of the kidney?
- Nephron
- Renal calculi
- Pelvis
- Ureter
How much filtrate is produced per hour?
7L - with only 100ml/hr urine
What receptors are found on all basement cell membranes of the kidney?
Na/K Pump
Where is EPO produced?
Paratubular cells
How is EPO produced?
- In response to drop in O2 levels in renal tissues
- Stimulate bone marrow to increase differentiation of precursors and therefore RBC
How is Vit D produced?
- Cholecalciferol produced from precursors
- Converted to 25-hydroxycholecalciferol in liver
- Converted to 1,25-dihydroxycholecalciferol in kidneys
What is the function of Vit D
- Inc Ca2+ (GI absorption, inc renal reabsorption, stim bone reabsorption)
What stimulates and inhibits Vit D production?
Stim: PTH
Inhib: High phosphate
How does the kidney allow for large amounts of filtration per day?
- High pressure filtration
- Filtration channels in podocytes
- Negatively charged membrane (cations and uncharged particles pass easily)
What does glomerular filtrate contain?
- Water
- Na, HCO3, glucose, amino acids
- In same conc as plasma
What should not be found in glomerular filtrate?
- Protein
- Cells
How is the filtrate initially produced at the Bowman’s capsule?
- Hydrostatic pressure 40mmHg
- Oncotic pressure 26mmHg
- Net filtration pressure 14mmHg into filtrate
What is the filtration fraction?
The proportion of renal plasma flow that is filtered
- Determines how much filtrate can be produced
What are the characteristics of a good marker of GFR?
- Readily filtered
- Not metabolised/reabsorbed/ secreted
- Filtration rate = rate of excretion
What is the glomerular filtration rate?
120-125ml/min
What are examples of GFR markers?
- Creatinine: produced at steady state from muscle breakdown, some overestimation
- Inulin: Freely filtered, more accurate, not naturally occurring
- Cystatin C: Produced by all cells
What are the auto regulation mechanisms?
- Myogenic: Stretch response
- Tubulo-glomerular feedback: Adenosine, PGE2, Angiotensin II
How does Adenosine act on the kidney?
- Released in normal hydrated state from macula densa
- Constricts afferent arteriole
- Reduces GFR
- Inhibits renin release
- Inhibited itself by fall in filtration flow- allows dilatation of afferent arteriole
How does PGE2 work?
- Produced in DCT in response to fall in filtration flow
- Dilates afferent arteriole to maintain blood flow
- Inhibited by NSAIDs
How does angiotensin II work on the kidneys?
- Produced by RAAS
- Constricts efferent arteriole to maintain capillary pressure & GFR
