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How the food changes consistency and form
Food changes consistency and form in the different parts of the digestive system. Through ingestion and mastication, food mixes with the amylase in saliva, which then reduces the food to a flexible, semi-solid lump, and easily swallowed ball called bolus. Upon swallowing, muscle contractions in the pharynx then pushes the bolus towards the esophagus and into the stomach where it undergoes further breakdown when mixed with gastric juice. Churning and hydrolysis then occurs, transforming the bolus into chyme. The chyme is then released into the small and large intestines where nutrients and water, ions, and vitamin K are absorbed. Once the nutrients are absorbed from the chyme, the remaining liquid waste material in the intestine turns into a semi-solid form called feces.
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How the body was able to absorb the nutrients from the foods we eat.
Due to its structure, most digestion and nutrient absorption occur in the small intestine. Its length, together with its circular folds, villi, and microvilli provides a large surface area for these functions. Digestion occurs by moving food through the gastrointestinal tract where it is mixed with digestive juices like saliva and stomach acid. Through the aid of these juices, large food molecules break down into smaller molecules that the body can absorb through the walls of the small intestine and into the bloodstream, which delivers the nutrients to the other parts of the body.
References
National Institute of Diabetes and Digestive and Kidney Diseases. (2013, September). The Digestive System and How It Works. National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved November 25, 2022, from https://www.niddk.nih.gov/-/media/Files/Digestive-Diseases/Digestive_System_508.pdf
Tortora, G. J., & Derrickson, B. H. (2011). Principles of Anatomy and Physiology. Wiley.