How does the food change in consistency and form?
- The food we intake in the mouth undergoes mastication or chewing, the physical breakdown of food transforming it into a soft and flexible mass called the bolus. Then, chemical digestion occurs called hydrolysis in which the enzyme salivary amylase present in our saliva initiates the breakdown of complex molecules, specifically carbohydrates.
- In the stomach, churning occurs, grinding the food by the contraction of the muscles. Hydrolysis also takes place in the stomach, wherein the gastric juice transforms bolus into a semi-liquid composition called the chyme.
- In the small intestine, the chyme undergoes hydrolysis again wherein enzymes called amylase, proteases, and lipases break down carbohydrates, proteins, and fats respectively into smaller, absorbable units.
How could the body absorb the nutrients from the foods we eat?
- Stomach: The stomach absorbs alcohol, aspirin, and water directly through its lining in the epithelial cells.
- Small Intestine: Carbohydrates are broken down into simpler substances and absorbed into the bloodstream with the help of specific transporters. Proteins are absorbed through active transport (amino acids) and peptide transporters (small peptides). Fat-soluble vitamins are absorbed together with dietary fats, and water-soluble vitamins and minerals are absorbed via specific transporters. Water and electrolytes are absorbed through osmosis and active transport.