Which of the following happens first?Multiple choice question.filtrationtubular secretiontubular reabsorption

To determine which of the processes occurs first among filtration, tubular secretion, and tubular reabsorption, it is important to understand the order of operations in the nephron, which is the functional unit of the kidney.

1. Filtration occurs first in the nephron. This is the process where blood passes through the glomerulus, and water, ions, and small molecules are filtered out into the Bowman's capsule, forming what is known as the filtrate.

2. Tubular reabsorption follows filtration. After the filtrate is formed, useful substances like glucose, amino acids, and most of the water and salts are reabsorbed back into the bloodstream in the renal tubules.

3. Tubular secretion occurs last. This process involves the transfer of substances from the blood into the tubular fluid, allowing waste products and excess ions to be excreted.

Final Answer

The correct order is: filtration occurs first, followed by tubular reabsorption, and then tubular secretion. Thus, the answer to the question is filtration.