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Contents:
  1. The Digestion and Absorption Process - Medicine LibreTexts
  2. From the Mouth to the Stomach
  3. The Physical Processes of Digestion
  4. Understanding Chemical Digestion
  5. Related Study Materials

The internal tissue of the small intestine is covered in villi, which are tiny finger-like projections that are covered with even smaller projections, called microvilli Figure 2. The digested nutrients pass through the absorptive cells of the intestine via diffusion or special transport proteins.

The Digestion and Absorption Process - Medicine LibreTexts

Amino acids, minerals, alcohol, water soluble vitamins, and monosaccharides sugars like glucose are transported from the intestinal cells into capillaries, but the much larger emulsified fatty acids, fat-soluble vitamins, and other lipids are transported first through lymphatic vessels, which soon meet up with blood vessels. The process of digestion is fairly efficient. The main task of the large intestine is to reabsorb water. Remember, water is present not only in solid foods but also the stomach releases a few hundred milliliters of gastric juice and the pancreas adds approximately another milliliters during the digestion of the meal.

For the body to conserve water, it is important that the water is reabsorbed. In the large intestine, no further chemical or mechanical breakdown of food takes place, unless it is accomplished by the bacteria that inhabit this portion of the digestive tract. The number of bacteria residing in the large intestine is estimated to be greater than 10 14 , which is more than the total number of cells in the human body 10 This may seem rather unpleasant, but the great majority of bacteria in the large intestine are harmless and some are even beneficial.

The bacteria synthesize the essential nutrient, vitamin K, short chain fatty acids, which are essential for our health, from the undigested fiber. Also, minerals, such as sodium and potassium, are absorbed. There has been significant talk about pre- and probiotic foods in the mainstream media. The World Health Organization defines probiotics as live bacteria that confer beneficial health effects on their host. They are added as live cultures to certain fermented foods such as yogurt.


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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. Examples of prebiotics would be inulin, soluble fiber and resistant starch.

From the Mouth to the Stomach

A review article in the June issue of the Journal of Nutrition concludes that there is a scientific consensus that probiotics ward off viral-induced diarrhea and reduce the symptoms of lactose intolerance. Farnworth, E. Expert nutritionists agree that more health benefits of pre- and probiotics will likely reach a scientific consensus. You may be interested in trying some of these foods in your diet.

Digestion Intro Mecahnical and Chemical Digestion

A simple food to try is kefir. After a few hours in the stomach, plus three to six hours in the small intestine, and about sixteen hours in the large intestine, the digestion process enters step four, which is the elimination of indigestible food as feces. Feces contain indigestible food and gut bacteria almost 50 percent of content. It is stored in the rectum until it is expelled through the anus via defecation. Digestion involves two processes - physical and chemical.

The Physical Processes of Digestion

During the physical process, the food is mixed and moved throughout the gastrointestinal tract. This process is also referred to as motility and the partially digested food is propelled by the wave-like action called peristalsis. Ring-like muscular valves called sphincters prevent the back flow of partially digested food and digestive juices. There are sphincters between the esophagus and stomach esophageal sphincter , between the stomach and small intestine pyloric sphincter and small intestine and colon ileocecal sphincter.

The chemical process of digestion involves the release of water, acid, bicarbonate and enzymes to be mixed with the food to further break it down into smaller subunits. Chemical breakdown starts in the mouth where enzymes break down complex carbohydrate. In the stomach, water and acid are released to begin the breakdown of protein. A mucus lining protects the stomach from the corrosive acid. The mixture, also known as chyme, enters the small intestine where bicarbonate is introduced to neutralize the acid and enzymes are added to break chemical bonds.

Most small intestine digestive enzymes are produced in the pancreas and small intestine. Our nervous system and hormones control digestion. The nervous system consists of the central nervous system, and the peripheral nervous system. Our brain and spinal cord make up the central nervous system while the peripheral system lies outside the skull and vertebral column.

There are two components to the peripheral system: the somatic system that supplies the skin and muscle, and the autonomic system which supplies smooth muscle, cardiac muscle, and glands. The PSNS supplies signals to maintain normal function and conserve body processes. The SNS provides signals to accelerate the process. Our gastrointestinal tract receives signals from the central and autonomic systems as well as sends signals to these systems. Hormones are also involved in regulating digestion.

Understanding Chemical Digestion

Your digestive tract secretes hormones to control the release of digestive enzymes and juices. Here is a table of some hormones. Our appetite and hunger are controlled by a complex process that involves many signals. Here is a brief overview of that process. Decide whether you want to consume pre- and probiotic foods to benefit your health.


  1. Digestion Lab.
  2. From the Stomach to the Small Intestine;
  3. Digestive System Processes and Regulation | Anatomy & Physiology.
  4. Digestion - Wikipedia.
  5. Chemical Digestion: Definition, Purpose, Starting Point, and More.

Visit the websites below to help in your decision-making process. Defend your decision scientifically. Skills to Develop Sketch and label the major organs of the digestive system and state their functions. From the Mouth to the Stomach There are four steps in the digestion process Figure 2. From the Stomach to the Small Intestine When food enters the stomach, a highly muscular organ, powerful peristaltic contractions help mash, pulverize, and churn food into chyme.

The stomach has three basic tasks: To store food To mechanically and chemically break down food To empty partially broken-down food into the small intestine The length of time food spends in the stomach varies by the macronutrient composition of the meal. Video 2. Tools for Change: Kefir There has been significant talk about pre- and probiotic foods in the mainstream media. From the Large Intestine to the Anus After a few hours in the stomach, plus three to six hours in the small intestine, and about sixteen hours in the large intestine, the digestion process enters step four, which is the elimination of indigestible food as feces.

Processes of Digestion Digestion involves two processes - physical and chemical. Regulation of Digestion Our nervous system and hormones control digestion. Table 2. Hormone Origin Stimulus Action Gastrin Stomach Food, especially proteins, caffeine, spices, alcohol Stimulates stomach acids and enzymes Cholecystokinin CCK Small Intestine Fat and protein Stimulates pancreas and liver secretions enzymes and bile for protein and fat digestion Secretin Small Intestine Acid from stomach in small intestine Secretes bicarbonate to neutralize acid Gastric inhibitory protein GIP Small Intestine Fat and protein Inhibits gastric motility and secretion of gastric juices Our appetite and hunger are controlled by a complex process that involves many signals.

These components are processed by cells throughout the body into energy or are used as building blocks. The digestive system is composed of the mouth, pharynx, esophagus, stomach, small intestine, large intestine or colon , rectum, and anus. There are four steps in the digestion process: ingestion, the mechanical and chemical breakdown of food, nutrient absorption, and elimination of indigestible food.

Related Study Materials

The mechanical breakdown of food occurs via muscular contractions called peristalsis and segmentation. Enzymes secreted by the salivary glands, stomach, pancreas, and small intestine accomplishes the chemical breakdown of food. Additionally, bile emulsifies fats. Peristalsis is also part of mechanical digestion. This refers to involuntary contractions and relaxations of the muscles of your esophagus, stomach, and intestines to break down food and move it through your digestive system. Chemical digestion involves the secretions of enzymes throughout your digestive tract.

These enzymes break the chemical bonds that hold food particles together. This allows food to be broken down into small, digestible parts. Once food particles reach your small intestine, the intestines continue to move. This helps keep food particles moving and exposes more of them to digestive enzymes. These movements also help to move the digested food toward the large intestine for eventual excretion.

Digestion involves taking large portions of food and breaking them down into micronutrients small enough to be absorbed by cells. Chemical digestion breaks down different nutrients, such as proteins, carbohydrates, and fats, into even smaller parts:. Some people may lack certain enzymes used in chemical digestion. Chemical digestion begins in your mouth. As you chew, your salivary glands release saliva into your mouth. The saliva contains digestive enzymes that start off the process of chemical digestion.

In your stomach , unique chief cells secrete digestive enzymes. One is pepsin, which breaks down proteins. Another is gastric lipase, which breaks down triglycerides. In your stomach, your body absorbs fat-soluble substances, such as aspirin and alcohol. The small intestine is a major site for chemical digestion and absorption of key food components, such as amino acids, peptides, and glucose for energy.

There are lots of enzymes released in the small intestine and from the nearby pancreas for digestion. These include lactase to digest lactose and sucrase to digest sucrose, or sugar. It also absorbs vitamins, minerals, and water. Chemical digestion is a vital part of the digestive process. While mechanical digestion involves physical movements, such as chewing and muscle contractions, chemical digestion uses enzymes to break down food. You probably already know that protein's important. But how does your body process it? We explain the process and how to up your protein absorption.

Carbohydrates give your body energy to do everyday tasks. We explain the process of carbohydrate digestion and how many carbs you should aim to eat…. It takes about 40 hours for fats to be digested in your body, though digestion time varies between men and women.