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How the food changes consistency and form.
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Digestion is the process where we break down foods into nutrients by different enzymes. Out of the six activities of digestion, there are four of them, including the processes of digestion that shows how our foods changes its consistency and form:
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Ingestion — the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with saliva, which contains enzymes that begin breaking down the carbohydrates in the food plus some lipid digestion via lingual lipase. Chewing increases the surface area of the food and allows an appropriately sized bolus to be produced.
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Propulsion — the movement of food through the digestive tract. It includes both the voluntary process of swallowing and the involuntary process of peristalsis. Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along. These waves also play a role in mixing food with digestive juices.
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Mechanical digestion — occurs in the mouth that results from chewing, or mastication in which food is manipulated by the tongue, ground by the teeth, and mixed with saliva. As a result, the food is reduced to a soft, flexible, easily swallowed mass called a bolus (lump). Food molecules begin to dissolve in the water in saliva, an important activity because enzymes can react with food molecules in a liquid medium only. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme.
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Chemical digestion — starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks. Two enzymes, salivary amylase that initiates the breakdown of starch and lingual lipase that breaks down dietary triglycerides (fats and oils) into fatty acids and diglycerides, contribute to chemical digestion in the mouth.
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How the body was able to absorb the nutrients from the foods we eat.
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After undergoing mechanical and chemical digestion, the foods then come in contact with a long tube called the small intestine. The structural features responsible for facilitating the process of digestion and absorption are the circular folds, villi, and microvilli. The small intestine absorbs most of the nutrients in your food, and your circulatory system passes them on to other parts of your body to store or use. Special cells help absorbed nutrients cross the intestinal lining into your bloodstream. Your blood carries simple sugars, amino acids, glycerol, and some vitamins and salts to the liver. Your liver stores, processes, and delivers nutrients to the rest of your body when needed.
References:
National Institute of Diabetes and Digestive and Kidney Diseases. (August 29, 2022). Your Digestive System & How it Works. Retrieved from https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works#:~:text=The%20small%20intestine%20absorbs%20most,intestinal%20lining%20into%20your%20bloodstream.
Rice University. (2017). Anatomy and Physiology. Houston Texas, HTX: Openstax
Tortora, G. & Derrickson, B. (2014). Principles of Anatomy and Physiology (14th ed.). New Jersey, NJ: Wiley