Renal - Physiology Flashcards
Outline anatomy of glomerulus
- Epithelial pouch invaginated by capillary tuft
- Semi-permeable filter: Endothelium, Basement membrane, Epithelium
-Mesangial cells are specialised smooth muscle cells that
support the glomerulus and regulate blood flow and GFR
Outline the details of filtration at the glomerulus
-Receive 25% of CO (1200ml/min)
-20% of blood volume is filtered (~250ml/min)
-GBM is –vely charged → retention of anionic proteins
such as albumin which are small enough to pass.
-Filtration is key to excretion of waste and remains
constant over a range of pressures (80-200mmHg).
-Flow will depend on Na and water reabsorption
What is main factor determining extra cellular volume and what mechanism does it use?
- Na: main factor determining extracellular volume
- ↓BP and ↓NaCl @ macula densa (DCT) → renin release → aldosterone release → more Na/K pumps.
What factor determines ECF osmolality and by what mechanism is this achieved?
- Water: Determines ECF osmolality
- ↑osmolality or ↓BP → ADH release
Descrine what is reabsorbed at the PCT
- Reabsorption of filtrate
- 70% of total Na+ reabsorption
- Reabsorption of amino acids, glucose, cations
- Bicarbonate reabsorbed using carbonic anhydrase
Describe what is reabsorbed in the TAL
- creation of osmolality gradient
- 20% of Na reabsorption
- Na/K/2Cl triple symporter
DCT: what is reabsorbed and created?
- pH and Ca reabsorbed
- 5% of Na reabsorption
- Apical NaCl co -transporter
- Ca2+ reabsorption under control of PT
Medullary collecting duct: what is reabsorbed and created?
- pH and K+ regulation
- Na reabsorption coupled to K or H excretion
- Basolateral aldosterone-sensitive Na/K pump
Cortical collecting duct: what is regulated?
-Regulation of water re-absorption via auqaporin 2 channels
What is the endocrine function of kidney?
-Secretion of renin by juxtaglomerular apparatus
-EPO synthesis
-1
α-hydroxylation of vitamin D (controlled by PTH)
Diuretics - carbonic anhydrase inhibitors
- Name
- MOA
- Effect
- Use
- S/E
- Acetazolamide
- MOA: inhibit carbonic anhydrase in PCT
- Effect: ↓ HCO3 reabsorption → small ↑ Na loss
- Use: glaucoma
- SE: drowsiness, renal stones, metabolic acidosis
Diuretics - loop diuretics
- Name
- MOA
- Effect
- Use
- S/E
- Furosemide/bumetanide
- MOA: inhibits Ma/K/2Cl symporter in thick ascending limb
- Effect: massive NaCl excretion, Ca and K+ excretion
- Use: Rx of oedema, CCF, nephrotic syndrome and hypercalcaemia
- S/E: Hypokalaemic metabolic alkalosis, ototoxic, hypovolaemia
Diuretics: Thiazides
- Name
- MOA
- Effect
- Use
- S/E
- Bendroflumethazide
- MOA: inhibits NaCl co-transporter in DCT
- Effect: moderate NaCl excretion, high Ca reabsorbed
- Use: HTN, mild oedema
- S/E: hypokalaemia, hyperglycaemia, raised urate (gout)
Diuretics: K sparing
- name
- MOA
- Effect
- Use
- S/E
-Spironolactone/amiloride
-MOA: Spiro (aldosterone antagonist), amiloride (blockers DCT/CD luminal Na+ channel
-Effect: increased Na excretion, and decreased K+ and H+ excretion
Use: used with loop or thiazides diuretics to control K+ loss. Spiro has long term benefits in aldosteronism (LF/HF)
-SE: hyperkalaemia, anti-androgenic (eg gynaecomastia)
Osmotic diuretics
- Name
- Effect
- Use
- Se
- Mannitol
- MOA: freely filtered and poorly reabsorbed
- Effect: decreases fluid volume in brain and lowers ICP
- Use: glaucoma, raised ICP, rhabdomyolysis
- SE: hyponatraemia, pulmonary oedema and N/V
