1. How does the food change in consistency and form?
Food undergoes significant changes in consistency and form during digestion in the mouth. Starting with mechanical breakdown, a person chewing reduces their food into small pieces, creating a soft mass called bolus. This is done with the aid of saliva, which moistens the food, making it easier to sallow and initiate chemical breakdown. Next is chemical digestion. Salivary amylase present in saliva converts the starches in the food into smaller molecules such as maltose, maltotriose, and such. Saliva also contains lingual lipase which acts on the food after the food is swallowed. It is responsible for the breakdown of dietary fats into fatty acids and diglycerides.
2. How could the body absorb the nutrients from the foods we eat?
In the stomach, food is mixed with gastric juice to form chyme, where pepsin breaks down proteins into small peptides, and acidic conditions help denature proteins for easier digestion. This chyme then enters the small intestine, where pancreatic enzymes and bile from liver and gallbladder further break down carbohydrates, fats, and proteins into their more basic forms (monosaccharides, amino acids, and fatty acids). These molecules are absorbed through the intestinal walls into the bloodstream and transported to cells for energy, growth, and repair.
References:
Tortora, G. J., & Derrickson, B. H. (2017). Tortora’s Principles of Anatomy and Physiology. In John Wiley & Sons, Inc. eBooks. https://ci.nii.ac.jp/ncid/BB23861293