Efferent arteriole
Glomerulus · Ang II constricts Raises FF
Drains the glomerular capillaries and forms a second resistance vessel before breaking up into the peritubular capillaries (cortical nephrons) or the vasa recta (juxtamedullary nephrons). Angiotensin II constricts it preferentially, which is how GFR is defended when renal perfusion falls.
Detail
- Constrictor
- Angiotensin II (efferent more than afferent): raises P_GC and filtration fraction, lowers peritubular hydrostatic and raises peritubular oncotic pressure
- Effect of constriction
- GFR maintained or raised while renal plasma flow falls; filtration fraction rises
- Dilators
- Adenosine via A2 receptors; ACE inhibitors and ARBs remove angiotensin II tone
- Downstream
- Peritubular capillaries in the cortex; descending vasa recta from juxtamedullary glomeruli
When it goes wrong
ACE inhibitor or ARB in bilateral renal artery stenosis (or stenosis of a single functioning kidney)
Efferent dilatation collapses net filtration pressure: creatinine rises sharply, acute kidney injury; in other patients a creatinine rise of up to ~30% after starting is accepted
Angiotensin II blockade in diabetic or proteinuric nephropathy
Lower intraglomerular pressure and proteinuria: the basis of renoprotection
Practise this structure
1 question in the bank tagged Glomerular Filtration.