You are watching: What are the four stages of digestion
Digestion begins even prior to you placed food right into your mouth. As soon as you feel hungry, your body sends out a blog post to your brain that that is time to eat. Sights and smells influence your body’s preparedness because that food. Odor food sends a article to your brain. Your brain then tells the mouth to obtain ready, and also you begin to salivate in ready for a delicious meal.
Figure 2.3.1: The digestion Process. Cradle converts the food us eat right into smaller particles, which will be processed into power or used as structure blocks.
Once you have eaten, your digestive mechanism (Figure 2.3.1) breaks under the food into smaller components. An additional word because that the breakdown of facility molecules right into smaller, less complicated molecules is "catabolism". To do this, catabolism features on two levels, mechanical and chemical. When the smaller sized particles have been broken down, they will certainly be soaked up into the blood and also delivered to cell throughout the human body for energy or for building blocks required for cell to function. The digestive system is just one of the eleven body organ systems of the human body and also it is composed of several hollow tube-shaped organs consisting of the mouth, pharynx, esophagus, stomach, tiny intestine, big intestine (or colon), rectum, and also anus. That is lined v mucosal tissue that secretes digestive juices (which aid in the failure of food) and mucus (which facilitates the propulsion the food with the tract). Smooth muscle organization surrounds the cradle tract and its convulsion produces waves, known as peristalsis, that propel food under the tract. Nutrients and some non-nutrients space absorbed. Building material such together fiber get left behind and are accordingly excreted.
From the Mouth come the Stomach
There are four steps in the digestion process (Figure 2.3.2). The first step is ingestion, which is the repertoire of food right into the digestive tract. It may seem a simple process, yet ingestion requires smelling food, thinking around food, and the involuntary release of saliva, in the mouth come prepare because that food entry. In the mouth, wherein the 2nd step of digestion occurs, the mechanical and chemical break down of food begins. The chemical malfunction of food involves enzymes, which break apart the materials in food. In the mouth, the enzyme amylase is secreted to start breaking down complex carbohydrate. Mechanical break down starts through mastication (chewing) in the mouth. Teeth crush and also grind large food particles, when saliva initiates the chemical malfunction of food and permits its activity downward. The slippery mass of partly broken-down food is called bolus, i beg your pardon moves under the digestive tract together you swallow. Swallowing may seem voluntarily at an initial because the requires mindful effort to push the food with the tongue earlier toward the throat, however after this, swallowing proceeds involuntarily, definition it can not be stopped when it begins.
Figure 2.3.2: The human being Digestive device : © Networkgraphics
As friend swallow, the bolus is driven from the mouth with the pharynx and into a muscular tube dubbed the esophagus. As it travels with the pharynx, a little flap called the epiglottis closes, to prevent choking by maintaining food native going into the trachea. Peristaltic contractions in the stomach propel the food down to the stomach. At the junction in between the esophagus and also stomach, there is a sphincter muscle that continues to be closed till the food bolus approaches. The press of the food bolus stimulates the reduced esophageal sphincter to relax and open and also food climate moves from the esophagus right into the stomach. The mechanical breakdown of food is accentuated through the muscular contractions the the stomach and tiny intestine the mash, mix, slosh, and propel food down the alimentary canal. Heavy food takes between four and eight secs to travel down the esophagus, and liquids take around one second.
The small intestine is split into 3 structural parts: the duodenum, the jejunum, and the ileum. As soon as the chyme start the duodenum (the an initial segment of the little intestine), 3 accessory (or helper) organs: liver, pancreas, and gallbladder are stimulated to release juices that aid in digestion. The pancreas secretes approximately 1.5 liters that pancreatic juice v a duct into the duodenum every day. This fluid consists mostly that water, however it additionally contains bicarbonate ion that neutralize the acidity of the stomach-derived chyme and also enzymes the further malfunction proteins, carbohydrates, and lipids. The gallbladder secretes a lot smaller lot of bile to help digest fats, additionally through a duct the leads to the duodenum. Bile is do in the liver and stored in the gallbladder. Bile’s contents act choose detergents by surrounding fats similar to the means dish soap removes grease indigenous a frying pan. This permits for the activity of fat in the watery environment of the little intestine. 2 different types of muscular contractions, dubbed peristalsis and also segmentation, move and mix the food in miscellaneous stages the digestion with the small intestine. Similar to what occurs in the esophagus and also stomach, peristalsis is circular tide of smooth muscle contraction that propel food forward. Segmentation sloshes food back and soon in both directions fostering further mix of the chyme. Practically all the materials of food are fully broken under to their most basic unit within the first 25 centimeters that the little intestine. Instead of proteins, carbohydrates, and also lipids, the chyme now consists of amino acids, monosaccharides, and also emulsified fat acids.
The next step of digestion (nutrient absorption) takes location in the remaining size of the tiny intestine, or ileum (> 5 meters).
Figure 2.3.3: The way the little intestine is structured provides it a huge surface area to maximize nutrient absorption. The surface area is enhanced by folds, villi, and also microvilli. Digested nutrient are soaked up into either capillaries or lymphatic vessels included within each microvilli. © Shutterstock
The tiny intestine is perfectly structured because that maximizing nutrient absorption. Its surface ar area is better than 200 square meters, i m sorry is about the size of a tennis court. The surface area that the tiny intestine rises by multiple levels of folding. The interior tissue that the tiny intestine is covered in villi, which room tiny finger-like projections that room covered with also smaller projections, called microvilli (Figure 2.3.3). The digested nutrient pass through the absorptive cells of the intestine via diffusion or special transport proteins. Amino acids, minerals, alcohol, water dissolve vitamins, and also monosaccharides (sugars prefer glucose) space transported from the minister cells right into capillaries, but the much larger emulsified fat acids, fat-soluble vitamins, and other lipids are transported very first through lymphatic vessels, i beg your pardon soon fulfill up v blood vessels.
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Figure 2.3.4: Kefir, a dairy product fermented v probiotic bacteria, can make a satisfied tasting milkshake. (CC BY-SA 3.0; Quijote )
You may be interested in trying several of these foods in your diet. A straightforward food to try is kefir. Several websites provide an excellent recipes, consisting of www.kefir.net/recipes.htm.