Digestion is the biological process of breaking down food into smaller, absorbable components that the body can utilize for energy, growth, and repair. In mammals, the digestion of proteins occurs through several stages in the alimentary canal.

1. **Mouth**: The digestion process begins in the mouth, where food is mechanically broken down by chewing. Saliva, which contains the enzyme **salivary amylase**, primarily aids in carbohydrate digestion; however, protein digestion does not occur here.

2. **Stomach**: Protein digestion primarily occurs in the stomach. Here, gastric juice is secreted, containing **hydrochloric acid (HCl)** and the enzyme **pepsinogen**. HCl activates pepsinogen into **pepsin**, which breaks down proteins into smaller peptides. The acidic environment also helps denature proteins, making them more accessible for enzymatic action.

3. **Small Intestine**: The digestion of proteins continues in the small intestine. **Pancreatic juices** are released, containing proteolytic enzymes such as **trypsin**, **chymotrypsin**, and **carboxypeptidase**. These enzymes further break down peptides into smaller peptides and amino acids. The walls of the small intestine also produce **peptidases**, which complete the digestion of peptides into individual amino acids.

4. **Absorption**: The amino acids produced are absorbed through the intestinal lining into the bloodstream, where they are transported to various tissues for use in protein synthesis and other metabolic functions.

Through these stages, the body efficiently converts dietary proteins into usable amino acids, which are essential for various physiological functions.