1. How the food changes consistency and form
When food is first taken into the mouth, it already changes its form as it is broken down physically by the chewing of teeth and chemically by salivary amylase. From there the food becomes soft and moist and is then swallowed when the tongue pushes the food into the throat or the pharynx as the epiglottis closes the trachea which is the opening to the lungs. The food is the called bolus, which is a ball-like mixture of food that travels into the esophagus where it is propelled down the digestive tract by peristalsis, a wavelike motion of contraction and relaxation of muscles in the wall of organs. From the esophagus it enters the stomach where food is mechanically digested by churning and chemically by gastric juices. The food is now broken down into a semifluid called chyme then it travels into the small intestine where most chemical digestion takes place and absorption of nutrients and water through the lining occurs. Afterwards, food goes into the large intestine where water is again re-absorbed, and numerous healthy bacteria can be found to aid digestion so that only the solid materials are left when it reaches the last section of the large intestine called the rectum. The solid material with undigested materials such as extracellular waste will then be eliminated through feces which is a solid waste of the body.
2. How the body was able to absorb the nutrients from the foods we eat
The human body is not capable of absorbing large complex molecules; thus, digestion takes place in order for us to breakdown complex molecules found in food into simpler forms that can be absorbed by the body where we are able to acquire nutrients. After food is physically and chemically broken down by the mouth as salivary amylase digests starch into maltose, by the stomach as pepsin breaks down proteins, together with the help of the accessory organs such as the liver which produces bile that helps breakdown fat, food then enters the small intestine as a semifluid called chyme where it is found to absorb biomolecules in simpler forms such as amino acids and glucose. Through the lining of the small intestine, nutrients are absorbed, including water. Through transport processes, the nutrients or substances are absorbed through the intestinal cell plasma membranes. Fatty acids and glycerol then go into the lymphatic system. The large intestine then once again re-absorbs water and it also absorbs Vitamin K, B, and some ions.