Anatomy and Physiology II Practice Test

Which part of the kidney is primarily responsible for urine filtration?

1. Renal pelvis

2. Renal cortex

3. Glomerulus

4. Renal medulla

The correct answer is: Glomerulus

The glomerulus is the primary structure responsible for urine filtration in the kidney. It is a network of tiny blood vessels (capillaries) located within the nephron, the functional unit of the kidney. During the filtration process, blood enters the glomerulus through the afferent arterioles. The high pressure within the glomerular capillaries forces water, ions, and small molecules out of the blood and into the Bowman’s capsule, which is the beginning of the nephron. This initial filtrate, often called glomerular filtrate, contains waste products, excess salts, and other substances that the body needs to eliminate. The filtration process is selective, allowing only certain substances to pass while retaining larger molecules, such as proteins and blood cells, within the bloodstream. In contrast, other parts of the kidney, like the renal pelvis, renal cortex, and renal medulla, serve different functions. The renal cortex contains the bulk of the nephron structures where reabsorption and secretion occur after initial filtration, while the renal pelvis is a collection area for urine before it moves to the ureter. The renal medulla contains the loop of Henle and collecting ducts, which play roles in concentrating urine but are not involved in