Final answer:
The absorption of dietary calcium in the duodenum is aided by 1, 25 (OH)₂ vitamin D, acidic environments, and the consumption of lactose. These factors help maintain a normal calcium concentration by improving calcium solubility and enhancing active transport mechanisms in the intestine.
Step-by-step explanation:
The absorption of dietary calcium in the duodenum is aided by 1, 25 (OH)₂ vitamin D. This form of vitamin D is particularly important because it enhances the absorption of calcium from the intestine and thus maintains a normal calcium concentration in the body.
The process of absorption involves the active transport of calcium and the production of specific calcium-binding proteins in the small intestine, which are synthesized under the influence of vitamin D. Factors such as acidic environments also favour calcium absorption as calcium salts are more soluble in acidic solutions. Additionally, the consumption of lactose and certain dietary proteins can increase the absorption of calcium.