Final answer:
Acute glomerulonephritis is an inflammation of the glomeruli of the nephrons. Immune complex deposition in the glomeruli is the main pathophysiological mechanism in acute glomerulonephritis. It is not caused by inflammation of the renal tubules, obstruction of the ureters, or enlargement of the renal pelvis.
Step-by-step explanation:
Acute glomerulonephritis is an inflammation of the glomeruli of the nephrons. It occurs when the glomeruli are damaged from inflammation, which can be caused by various factors such as infections or autoimmune disorders. The main pathophysiological mechanism in acute glomerulonephritis is immune complex deposition in the glomeruli, where immune complexes formed in the blood trigger an inflammatory response in the capillary endothelial cell junctions of the glomeruli.