Glomerulonephritis is primarily an inflammation of which part of the kidneys?

Glomerulonephritis is primarily an inflammation of the glomerulus, which is a network of tiny blood vessels located within the nephron of the kidney. The glomerulus is responsible for filtering blood to form urine, making it crucial to kidney function. In glomerulonephritis, inflammation can lead to damage in the glomeruli, subsequently affecting their ability to filter waste effectively, which may result in symptoms such as hematuria (blood in urine), proteinuria (excess protein in urine), and reduced kidney function.

The other options refer to structural components of the kidneys or urinary system that are not directly involved in glomerulonephritis. The renal pelvis is the area of the kidney where urine collects before moving to the ureters, whereas the renal cortex is the outer layer of the kidney containing various structures, including parts of nephrons but not specifically the glomerulus. The ureters are tubes that carry urine from the kidneys to the bladder and are not part of the kidney's internal filtering system. Thus, the correct answer highlights that glomerulonephritis specifically targets the glomerulus within the nephron structure.