How does the food change in consistency and form?
The digestive system’s main function is to breakdown food and turn it into nutrients that the body can absorb. As food undergoes the digestive process, its form and consistency are continuously changed and modified as it moves through the digestive tract. Through a series of digestive mechanisms known as mechanical and chemical digestion, this breakdown process is made possible by the organs involved. This process begins in the mouth as food is taken and mechanically broken down into smaller pieces through chewing. Chemical digestion becomes involved through the saliva, which adds digestive enzymes like amylase, water, and mucus to the food, reducing it into smaller particles. The chewed food turns into a “bolus," a soft and rounded form of food that is swallowed and continues to be broken down in a series of muscle contractions or peristalsis in the esophagus. Afterwards, the broken-down food reaches the stomach, where it is broken down further into a semi-liquid substance called “chyme.” The stomach continues the digestion with both mechanical and chemical digestion characterized by muscle contractions and the utilization of gastric juices and digestive enzymes to break the proteins into smaller peptides, respectively. The journey of the chyme does not end there but continues to travel through the small intestine, where it undergoes further breakdown into simpler forms as amino acids, fatty acids, and simple sugars. In this form, it is absorbed by the small intestine as nutrients. The indigestible materials from the small intestine will then move into the large intestine, where the remaining water from the undigested food is absorbed, forming the solid fecal mass that is stored in the rectum before elimination and will be released through the anus.
How could the body absorb the nutrients from the foods we eat?
The absorption of nutrients from foods takes place mostly in the small intestine. As the chyme from the stomach arrives in the small intestine, the absorption begins in the duodenum, where it is mixed with the bile that emulsifies the fats, and the pancreatic juices break down the proteins, carbohydrates, and fats into smaller molecules. These nutrients are then absorbed in the jejunum and ileum, which are equipped with microvilli that are mainly responsible for helping nutrients to pass through and be absorbed into the bloodstream. Although most of the nutrients are absorbed here, some nutrients that were not absorbed from the undigested substances will be taken to the colon or large intestine for further absorption and will also be transported to the blood for circulation.