Chapter 3: The Digestive System

Chapter 3: The Digestive System


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criticism commentary news reporting teaching scholarship or research. Chapter 3 Anatomy for Nutrition’s Sake
presented by Tiana Glanton and Jennifer Arteaga Section 3.0 Essential Nutrients
Essential nutrients are part of our basic needs for life. All of our body
processes depend on ourselves functioning properly and in order for
them to do so they must have what they need to get the job done. For example in
digestion our cells make up our tissues and organs that work together to supply
our body with energy water and essential nutrients. Our basic cell needs our
energy, water, oxygen, and essential nutrients. Our cells cannot make
essential nutrients which means we must provide them by the foods we eat. This is
the first principle of nutrition. Our bodies specifically use essential nutrients to make new cells and new cell parts. Section 3.1 The Digestive System Specific cells in the hypothalamus detect when the body’s cells are deprived of fuel. The cells then signal hunger to the conscious part of the brain. Hunger an involuntary action and appetite a voluntary action are experienced in the cortex of the brain. The digestive system is made up of the gastrointestinal (GI) tract also called the digestive tract, the liver, pancreas, and the gallbladder. Food moves through the digestive system by the GI tract. The GI tract consists of the mouth. This is where the digestive processes begins. The mouth is designed for physical breakdown of foods. Teeth cut off a bite-sized portion and then, aided by the tongue, grind it finely enough to be mixed with saliva and swallowed. Chewing is important for foods with indigestible membranes and exposing the surface area of food to digestive secretions. When food is chewed, the result is a mixture of food particles and saliva called bolus. This complete process occurs in less than two seconds. The esophagus, no digestion occurs here. Its purpose is strictly to serve as a vehicle for the food bolus as it travels from the mouth to the stomach. During the swallowing process, a sphincter at the top of the esophagus relaxes to permit the bolus to enter. At the lower end of the esophagus circular muscles from the lower esophageal sphincter, which is normally constricted or closed, plays an important role in protecting the esophagus from stomach acid that might otherwise splash back into the esophagus. The stomach carries out three jobs. It stores a sizable amount of food until it can be processed; forms a mixture of food and gastric secretions, which becomes a semi-liquid blend called chyme (KIME); and controls movement of the chyme into the small intestine at a rate suitable for proper digestion and absorption by the small intestine. The small intestine is the organ of digestion and absorption; it finishes the job that the mouth and stomach started. Chyme must touch the walls of the small intestine to make contact with the secretions and to be absorbed at the proper places. At the end of the small intestine, a circular muscle called ileocecal valve controls the flow of the contents going into the large intestine.The large intestine under normal circumstances, all chemical digestion has been completed by the time chyme reaches the large intestine. No digestive enzymes are secreted. The primary functions of the large intestine are to absorb dissolved minerals and water and eliminate waste products. Cells lining the colon are specialized for absorbing these minerals and retrieving water for recycling. Accessory organs of digestion are the liver. The liver determines the metabolic fate of every nutrient we digest and absorb. It also creates bile that helps neutralize acidic chyme in the intestinal tract. Bile is made up of water, bile salts, bile pigments, and cholesterol. Bile salts break down large globules of fat into tiny globules of fat. This improves the efficiency of fat digestion by increasing the surface area of fat. Bile salts also play a role in absorption of fat soluble vitamins. The gallbladder is a sac, attached to the liver where bile is stored and concentrated. Bile empties from the gallbladder into the uppermost part of the small intestine via the common bile duct. When the small intestine is empty, the sphincter is closed, and bile is backed up into the gallbladder for concentration and storage until it is needed. The pancreas a gland having endocrine and exocrine functions. Endocrine -regulate blood glucose levels through secretion of the hormones insulin and glucagon into the blood. Exocrine -bicarbonate and digestive enzymes that act on carbohydrates, proteins, and fats are secreted into the duodenum. Section 3.2 Metabolism So, metabolism is a very wide term. Metabolism is every biochemical reaction that happens in your body. But under metabolism when referring to what the body does with the food we eat we are talking about catabolism and anabolism. Catabolism is the metabolic process of breaking down bigger molecules to release the energy your body needs to maintain homeostasis and provide cells with fuel. Anabolism is the metabolic process that happens to what is not used in the catabolic process. When the body no long requires energy and/or has an excess of nutrients left over it builds compounds and stores them for later use. Both of these processes are examples of energy metabolism. Here is a basic visual of how these processes work in the body. First, we eat food to satisfy our bodies need to feed our cells nutrients to maintain homeostasis through our body processes. Second, our body immediately sends nutrients from food through capillaries and veins to our liver to be broken down further. Once these nutrients are in the liver, digestive enzymes break down carbohydrates into glucose, our body’s primary sugar and energy source, and fat into fatty acids and proteins into amino acids. All of this is an example of catabolism. These are all sent to different places in the body for various uses and more reactions occur. Finally, whatever is left is built back up mostly into fat and stored for immediate or later use whatever your bodies need may be this is an example of anabolism. Including the digestive system, the body has many more systems such as the bones, muscles, nerves and lungs. All of them work together so the cells can carry on its own life, assure that their needs will be met by the other cells, and do their own specialized work for the welfare of the whole. Most of the body’s work is done automatically and is finely regulated to achieve a state of well-being. To promote health, we should listen to our bodies and understand/ appreciate our body’s needs. As humans, 99 percent of our genetic physiology and metabolic heritage dates back roughly 40,000 years. Our gene pool has been programmed to perform in ancient surroundings significantly unlike those in which we now live. Take a look at the following comparison between the eating patterns of our ancient ancestors and those of today. The typical American diet can be wholly or partially linked to chronic diseases such as heart disease, some cancers, obesity, and type 2 diabetes. Chronic degenerative diseases do cause death later in life, but they begin much earlier in life, usually in our late teens and early 20s. In the following chart take a look at the protective attributes of ancient habits and eating patterns The foods we consume today are very different from the foods of the ancient past. The same thing that caused our ancestors to survive is killing us now. The following foods in the chart were generally unavailable to our ancestors. Section 3.4 Common Digestive Problems
And because of the nature of these next couple slides. Um, we just want to put out a disclaimer that we are not medical professionals and nothing here or anywhere in this presentation can be taken as medical or health advice, so check with your physician before following any advice or information you find in this presentation. Thank you. Choking is when a small piece of food or object goes down the wrong pipe (hence the saying). Instead of going down the esophagus it goes down the trachea, blocking your airway. If your brain goes without oxygen for more than 4 minutes you can suffer from brain damage and even death. You can prevent choking in yourself and others by following basic food etiquette rules. Like sitting when eating and not talking or laughing with your mouth full. You can also avoid eating or serving foods that have been deemed easy to choke on like hot dogs grapes popcorn to name a few. Babies and toddlers are at risk for choking and should always be supervised when eating. Help prevent a tragedy by making sure they don’t have access to hazardous items like coins, batteries, and toys with small parts to name a few. The best thing you can do for someone who is choking is learn the Heimlich maneuver and use it if the occasion arises and always in an emergency call for help and 9-1-1. All CPR certifications classes include learning the Heimlich maneuver. And this is the universal sign of choking pictured. So, if you see someone doing this they’re most likely choking.
And here we have what might be the despised of most common digestive problems, hiccups. Hiccups are a spasm of the diaphragm (the muscle directly below the lungs). The spasm causes a person to take a short, quick breath that is interrupted by the sudden closing of the epiglottis (this is where the recognizable hiccup sound comes from). There is no exact known cause of the hiccups, but some common causes are eating hot and spicy liquids and foods, swallowing air, excess smoking and drinking alcohol among some others. There is also no known cure but some suggested home remedies, that I’m sure you’ve heard of, that may or may not work they include, holding your breath for 10 seconds, drinking a glass of cold water quickly or eating a teaspoon of sugar or honey. Notice I didn’t include scaring someone or being suddenly scared (that doesn’t work). They usually disappear after several minutes but if they continue after a few days a healthcare provider should be consulted. Did you know that the average adult passes gas 14 to 23 times a day? Gas is basically air that has entered into our digestive tract. The air can enter because we were eating or drinking to quickly, chewing gum or smoking. Once air goes in it has to come out and it does in the form of gas. This can happen two ways. It either comes back up the esophagus and out of the mouth as a burp or belch, or it travels through the digestive tract. Ultimately ending up in the large intestine where it mixes with undigested food and friendly bacteria that live in our large intestine and finally out of the rectum as a fart or flatulence. But why does it smell so bad? The foul odor. That is associated with flatulence comes from small amounts of sulfur in our large intestine produced by those helpful bacteria living there. Some other causes of gas can be certain foods we eat there is a list on page 89 of the textbook that list these foods. Keep in mind though that our bodies are different and what might cause gas in some might not cause gas in others and the only way to find out is with trial and error.
When you hear that someone is lactose intolerant it means that their body cannot process the natural sugar in milk and some milk products. These people lack the enzyme lactase, necessary to break down lactose into absorbable components. When this nutrient reaches the large intestine without being broken down it causes all kinds of problems. The body tries to deal with this and in the process, causes bloating, diarrhea, gas and abdominal cramping.
Heartburn is a gastrointestinal condition that gets its name from the painful burning sensation that occurs in the esophagus just below or behind the sternum. Everyone most likely experiences heartburn at least once in their life. Frequent or chronic heartburn could be a sign of something more serious like GERD. GERD or Gastroesophageal reflux disease is when the sphincter muscles between the esophagus and the stomach don’t close all the way and this allows the acidic contents of the stomach to go back up into the esophagus and irritate it. Some of the symptoms include a burning sensation in throat, difficulty swallowing and a sensation of food getting caught in your throat or chest, among some others. Some irritants are spicy or acidic foods, caffeine, alcohol, lying down after a meal, large meals, some medications, and others. Some circumstances can also cause GERD like pregnancy, obesity, or tight clothing. You need to see a health care provider if you experience any other these symptoms for long term
constipation is the most common GI complaint in the U.S. It is a symptom, not a disease. It happens when the stool moving through the colon gets too dry and hard to move out of the rectum. It can also happen when the muscle contractions (that help move the stool out of the rectum) are too slow to rapidly and effectively move stool out of the colon. Some causes of constipation are inadequate diet, a diet lacking of fiber, water, or a diet with an excess of dairy. Another big cause of constipation is lack of physical activity. In most cases, constipation can be treated by changing your diet and life style; adding more fiber and water to to your diet and exercising regularly.
Hemorrhoids can be a result of straining that is associated with chronic constipation and even though they are not life threatening they can be very painful. Hemorrhoids are swollen and inflamed veins around anus or lower rectum. They can either be internal (inside the anus) or external (under skin around the anus). Symptoms of hemorrhoids can be bright red blood covering stool, on toilet paper or in toilet bowl. Another cause of hemorrhoids is pregnancy because of the pressure the fetus puts on the abdomen. Some treatments are to bathe in warm water for 10 minutes several times a day and apply a hemorrhoid cream. But you can prevent hemorrhoids by relieving constipation and pressure. And here are our references.

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