1. How the food changes consistency and form.
Food changes consistency and form as it enters and travels through the digestive system. Food is first ingested, entering the mouth, where it is masticated (mechanically digested) with the combined movements of the tongue and teeth, and then is mixed with saliva secreted by the salivary glands. This turns the food into a soft and easily swallowed mass called bolus. The bolus is then swallowed, first passing through the mouth and into the pharynx, which pushes the swallowed food into the esophagus, and then the stomach with the help of muscular contractions. The stomach is where digestion occurs--gastric juice further breaks down the food and reduces it to a soupy liquid called chyme. The chyme is then emptied from the stomach and into the small intestine so that the food can go through chemical digestion and its nutrients can be extracted. The leftover materials (water, fiber, dead cells) passes through the large intestine, which drains it of its fluids, leaving a soft mass called feces or stool. The stool will then be passed through the rectum, where it will be temporarily stored and later expelled.
2. How the body was able to absorb the nutrients from the foods we eat.
The small intestine is largely responsible for both the digestion and absorption of nutrients. It has a large surface area that has circular folds, villi, and microvilli.
Before absorption, however, it is necessary for food to be broken down into even smaller molecules. Bile, pancreatic juice, and intestinal juice completes the chemical digestion of carbohydrates, proteins, and lipids. Their small form can now pass through the small intestine's lining, allowing for absorption of nutrients in the form of monosaccharides, amino acids, fatty acids, etc. The digested nutrients then enter the bloodstream, which will be transported to the different parts of the body.