How the food changes consistency and form
As the food enters the mouth, it undergoes mechanical digestion by chewing, and it also becomes chemically digested when it is in touch with saliva. Saliva contains salivary amylase, which starts the digestion of starch in food.
After the food undergoes mastication and starch digestion, it will form a minor, round slurry mass called a bolus. Peristalsis causes it to move down the esophagus and into the stomach.
In the stomach, gastric juices initiate protein digestion. These juices mainly contain pepsin and hydrochloric acid. As the HCl may damage the stomach wall, the mucus turns secreted by the stomach, which provides a slimy layer that acts as a shield against the damaging effects of the acid.
Protein digestion coincides with mechanical mixing by peristalsis, which allows the mass of food to mix with the digestive enzymes. These enzymes continue breaking down the food and changing its consistency to liquid or paste.
After some time, a thick liquid called chyme is produced, which enters the duodenum, where it mixes with digestive enzymes from the pancreas and bile juice from the liver, and then passes through the small intestine. After the chyme becomes wholly digested, it gets absorbed into the blood.
How the body was able to absorb the nutrients from the foods we eat.
The mechanism of digestion is responsible for how nourishment is absorbed. The body breaks down food into molecules that may be absorbed physically and chemically. This mechanism consists of chewing food and stomach-churning in an acidic environment.
From here, nutrient absorption takes place. Between the stomach and the large intestine, in the gastrointestinal tract, lies the small intestine, which is where nutrients get absorbed by diffusion through its wall.
Minerals and nutrients from meals become absorbed through the small intestine, which serves this purpose primarily. Through diffusion, nutrients that have been ingested move across the blood vessels in the intestinal wall.
In the small intestine, columnar epithelial tissue lines the mucosa. Blood vessels carry the ingested nutrients and minerals throughout the body to various organs, which aids in creating the proteins, carbs, and lipids that the body needs. Then, food still undergoing processing and absorbed enters the large intestine.