1. How does the food change in consistency and form?
When food is ingested, it is mechanically broken down into smaller pieces through the process of mastication. Chemical breakdown also occurs as salivary amylase begins turning the starch in food into simpler sugars. The product of this is bolus– a semi-solid mass of chewed food mixed with saliva. The bolus then travels through the digestive system until it reaches the stomach, where stomach walls mix bolus and gastric juices to produce chyme– a semi-liquid mixture. The gastric juices such as HCl and pepsin breakdown proteins in the bolus into smaller peptides. Penultimately, in the small intestine, bile from the liver emulsifies fats while pancreatic enzymes contribute to the further breakdown of proteins, carbohydrates, and fats. Enzymes across the Ileum and Jejunum also contribute in the further digestion of nutrients into simpler forms. Finally, after passing through the intestines, the chyme has slowly hardened and resembles fecal matter. This fecal matter appearing as solid or semi-solid waste reaches the rectum, where it is defecated.
2. How could the body absorb the nutrients from the foods we eat?
Absorption of nutrients from the food we eat mainly occurs in the intestines. This happens when the chyme passes through the intestines where it to come in contact with the bile and digestive enzymes from the pancreas, the jejunum, and the ileum, where the nutrient absorption happens. The absorbed nutrients then travel to the bloodstream via the villi attached to the walls of the small intestine due to their connection with several capillaries.