14.2 Nutrition Basic Concepts
Open Resources for Nursing (Open RN)
Before discussing assessments and interventions related to promoting good nutrition, let’s review the structure and function of the digestive system, essential nutrients, and nutritional guidelines.
Digestive System
The digestive system breaks down food and then absorbs nutrients into the bloodstream via the small intestine and large intestine. Because good health depends on good nutrition, any disorder affecting the functioning of the digestive system can significantly impact overall health and well-being and increase the risk of chronic health conditions.
Structure and Function
The gastrointestinal system (also referred to as the digestive system) is responsible for several functions, including digestion, absorption, and immune response. Digestion begins in the upper gastrointestinal tract at the mouth, where chewing of food occurs, called mastication. Mastication results in mechanical digestion when food is broken down into small chunks and swallowed. Masticated food is formed into a bolus as it moves toward the pharynx in the back of the throat and then into the esophagus. Coordinated muscle movements in the esophagus called peristalsis move the food bolus into the stomach where it is mixed with acidic gastric juices and further broken down into chyme through a chemical digestion process. As chyme is moved out of the stomach and into the duodenum of the small intestine, it is mixed with bile from the gallbladder and pancreatic enzymes from the pancreas for further digestion.[1]
Absorption is a second gastrointestinal function. After chyme enters the small intestine, it comes into contact with tiny fingerlike projections along the inside of the intestine called villi. Villi increase the surface area of the small intestine and allow nutrients, such as protein, carbohydrates, fat, vitamins, and minerals, to absorb through the intestinal wall and into the bloodstream. Absorption of nutrients is essential for metabolism to occur because nutrients fuel bodily functions and create energy. Peristalsis moves leftover liquid from the small intestine into the large intestine, where additional water and minerals are absorbed. Waste products are condensed into feces and excreted from the body through the anus.[2] for labeled parts of the gastrointestinal system.
In addition to digestion and absorption, the gastrointestinal system is also involved in immune function. Good bacteria in the stomach create a person’s gut biome. Gut biome contributes to a person’s immune response through antibody production in response to foreign materials, chemicals, bacteria, and other substances.[3] For example, clients may develop Clostridium difficile (C-diff) after taking antibiotics that kill these beneficial bacteria in the gut. Read additional details about our microbiome and immune response in the “Infection” chapter of this book.
Essential Nutrients
Nutrients from food and fluids are used by the body