ACTIVITY 1: THE FOOD JOURNEY
1. How does the food change in consistency and form?
The digestive system is responsible for breaking down and absorbing the nutrients from the food that we ingest. The food undergoes mechanical and chemical digestion, allowing it to change in consistency and form. The process begins with mechanical digestion in the mouth as a result of mastication—a process that involves manipulation of the tongue, grinding of the teeth, and mixing saliva with the ingested food—wherein the food turns into bolus, a soft, flexible, and easily swallowed mass. Chemical digestion also occurs with the presence of two enzymes, salivary amylase and lingual lipase, which break down the swallowed food. In the stomach, the food particles undergo series of movements, propulsion and retropulsion, which reduce the size of the food particles, turning them into a soupy liquid called chyme. In the small intestine, segmentations mix chyme—which already contains partially digested carbohydrates, proteins, and lipids—and digestive juices together, allowing absorption to occur as the food particles come in contact with the mucosa; afterwards, peristalsis begins. From a semisolid state, the contents now have a liquid consistency due to water, bile, enzymes, and mucus after undergoing the process in the small intestine. As the chyme passes from the small intestine to the large intestine—beginning from the ileum—the walls, at a certain point, contract and squeeze the contents into the next haustrum, following a series of movements until it reaches the rectum. In the colon of the large intestine, the chyme is ready to be eliminated, eventually becoming solid or semisolid, now called feces. The result of the digestion process is the nutrient absorption into the bloodstream, which facilitates production of energy and metabolic processes in the body, as well as the defecation process or the elimination of the feces.
2. How could the body absorb the nutrients from the foods we eat?
Most of the nutrients in the food is absorbed in the small intestine. During the process of digestion, the food is broken down, and the nutrients from the food we eat are absorbed into the bloodstream. In the small intestine, there are microvilli, which contain several brush-border enzymes that aid in nutrient digestion. Moreover, the segmentation process occurs in the small intestine, wherein chyme is mixed with the digestive juices, and the particles of food make contact with the mucosa; hence, absorption takes place. The walls of the small intestine also enable nutrients to pass through and reach the cells of the body. After most of the meal has been absorbed, the nutrients will then be transported by the circulatory system to the rest of the body.
REFERENCE:
Tortora, G.J., & Derrickson, B. (2017). Principles of anatomy and physiology (15th ed.). Wiley.