Anatomy and Physiology II Practice Test

What is the process called that involves the movement of a substance from the renal tubules into the blood?

1. Secretion

2. Excretion

3. Reabsorption

4. Filtration

The correct answer is: Reabsorption

The process of moving a substance from the renal tubules into the blood is known as reabsorption. During this vital function, the kidneys filter blood, resulting in the formation of urine. However, not all of the substances that are initially filtered out are excreted. Instead, many essential nutrients, ions, and water are reabsorbed back into the bloodstream from the renal tubules. This ensures that the body retains necessary components such as glucose, amino acids, and specific ions, which might otherwise be lost in urine. Reabsorption primarily occurs in the proximal convoluted tubule and continues along the nephron, including the loop of Henle, distal convoluted tubule, and collecting duct. Hormonal regulation, especially by hormones such as aldosterone and antidiuretic hormone (ADH), plays a crucial role in adjusting the amount of reabsorption based on the body's needs for water and electrolytes. In contrast, secretion refers to the process where substances are moved from the blood into the renal tubules. Excretion is the process of eliminating waste products from the body via urine, while filtration is the initial step where blood is filtered to create filtrate in the renal corpuscle, allowing only specific substances to pass while retaining