Calcium absorption primarily occurs in which two locations of the body?

Calcium absorption primarily occurs in the small intestine, specifically in the duodenum and proximal part of the jejunum. The mechanisms involved in this process include both passive and active transport. The distal tubule of the nephron does play a role in the regulation of calcium levels through reabsorption, but it is not the primary site for absorption from the digestive tract.

The correct pairing emphasizes the roles of the small intestine, particularly the duodenum, where calcium absorption is maximized due to the presence of specific transport proteins and the influence of vitamin D. Vitamin D enhances the efficiency of calcium uptake from the intestinal lumen into the bloodstream.

Other locations mentioned in the incorrect choices, such as the large intestine or liver, do not significantly contribute to calcium absorption. In the context of renal function, the nephron has regulatory roles, but absorption of calcium predominantly happens in the intestinal tract rather than the urinary system. Therefore, the correct understanding centers around the major sites of calcium absorption being in the small intestine, highlighting their physiological importance in nutrient uptake.