![]() ![]() As the bolus travels through the pharynx, a small flap called the epiglottis closes to prevent choking by keeping food from going into the trachea. As you swallow, the bolus is pushed from the mouth through the pharynx and into a muscular tube called the esophagus. Swallowing may seem voluntary at first because it requires conscious effort to push the food with the tongue back toward the throat, but after this, swallowing proceeds involuntarily, meaning it cannot be stopped once it begins. The slippery mass of partially broken-down food is called a bolus, which moves down the digestive tract as you swallow. Teeth crush and grind large food particles, while saliva provides lubrication and enables food movement downward. Mechanical breakdown starts with mastication (chewing) in the mouth. The chemical breakdown of food involves enzymes, such as salivary amylase that starts the breakdown of large starch molecules into smaller components. In the mouth, where the second step of digestion starts, the mechanical and chemical breakdown of food begins. It may seem a simple process, but ingestion involves smelling food, thinking about food, and the involuntary release of saliva in the mouth to prepare for food entry. The first step is ingestion, which is the intake of food into the digestive tract. ![]() There are four steps in the digestion process (Figure 2.5 “The Human Digestive System”). Kefir, a dairy product fermented with probiotic bacteria, can make a pleasant tasting milkshake.įigure 2.5 The Human Digestive System Image by Allison Calabrese / CC BY 4.0 From the Mouth to the Stomach Several websites provide good recipes, including. You may be interested in trying some of these foods in your diet. As the fields of pre- and probiotic manufacturing and their clinical study progress, more information on proper dosing and what exact strains of bacteria are potentially “friendly” will become available. Įxpert nutritionists agree that more health benefits of pre- and probiotics will likely reach scientific consensus. A review article in the June 2008 issue of the Journal of Nutrition concludes that there is scientific consensus that probiotics ward off viral-induced diarrhea and reduce the symptoms of lactose intolerance. Prebiotics are indigestible foods, primarily soluble fibers, that stimulate the growth of certain strains of bacteria in the large intestine and provide health benefits to the host. ![]() They are added as live cultures to certain fermented foods such as yogurt. They are sometimes called “friendly bacteria.” The most common bacteria labeled as probiotic is lactic acid bacteria (lactobacilli). The World Health Organization defines probiotics as live bacteria that confer beneficial health effects on their host. There has been significant talk about pre- and probiotic foods in the mainstream media. Substances such as fiber get left behind and are appropriately excreted.įigure 2.4 Digestion Breakdown of Macronutrientsĭigestion converts components of the food we eat into smaller molecules that can be absorbed into the body and utilized for energy needs or as building blocks for making larger molecules in cells.Įveryday Connection Image by Gabriel Lee / CC BY-NC-SA Nutrients, as well as some non-nutrients, are absorbed. Smooth muscle tissue surrounds the digestive tract and its contraction produces waves, known as peristalsis, that propel food down the tract. It is lined with mucosal tissue that secretes digestive juices (which aid in the breakdown of food) and mucus (which facilitates the propulsion of food through the tract). The digestive system is one of the eleven organ systems of the human body, and it is composed of several hollow tube-shaped organs including the mouth, pharynx, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus. The smaller nutrient molecules can then be absorbed and processed by cells throughout the body for energy or used as building blocks for new cells. To do this, the digestive system functions on two levels, mechanically to move and mix ingested food and chemically to break down large molecules. Once you have eaten, your digestive system (Figure 2.4 “The Human Digestive System”) starts the process that breaks down the components of food into smaller components that can be absorbed and taken into the body. Your brain then tells the mouth to get ready, and you start to salivate in preparation for a meal. Smelling food sends a message to your brain. Sights and smells influence your body’s preparedness for food. When you feel hungry, your body sends a message to your brain that it is time to eat. The process of digestion begins even before you put food into your mouth.
0 Comments
Leave a Reply. |