Anatomy and Physiology II Practice Test

Where is most of the sodium in our internal secretion primarily reabsorbed?

1. Excreted in the urine

2. Excreted in the feces

3. Reabsorbed in the small intestine

4. Reabsorbed in the large intestine

The correct answer is: Reabsorbed in the large intestine

The majority of sodium reabsorption in the body primarily occurs in the kidneys, specifically within the renal tubules. However, within the context of the options provided, the most significant site for sodium reabsorption is the proximal convoluted tubule of the nephron, not specifically in the large intestine as indicated by the chosen answer. The erroneous choice implies that sodium is predominantly reabsorbed in the large intestine, which is functionally responsible for water and electrolyte balance, but it does not play a major role in sodium reabsorption compared to the kidneys. The small intestine does perform some sodium reabsorption, particularly through sodium-dependent transport mechanisms, but it is not the primary site in terms of the body's overall sodium handling. The correct understanding should highlight that while some sodium may be handled in both the small and large intestines, the kidneys are the primary site for sodium reabsorption, particularly during the filtration and reabsorption processes in the nephron. This process is crucial for maintaining electrolyte balance and blood pressure homeostasis.