International Foundation for Gastrointestinal Disorders. GI Disorders. Upper GI Disorders. Lower GI Disorders. Bowel incontinence Chronic constipation Chronic diarrhea Dyssynergic defecation. Other GI Disorders. Abdominal adhesions Acute Hepatic Porphyria Anal fistulas Celiac disease Clostridium difficile Congenital sucrase-isomaltase deficiency.
Malabsorption Opioid Induced Constipation Radiation therapy injury Scleroderma Short bowel syndrome Superior mesenteric artery syndrome. Vovulus Rare diseases.
Motility Disorders. Functional GI Disorders. The Digestive System. Reality Report from Miranda A. Why is digestion important When we eat such things as bread, meat, and vegetables, they are not in a form that the body can use as nourishment. How is food digested Digestion involves the mixing of food, its movement through the digestive tract, and the chemical breakdown of the large molecules of food into smaller molecules. The third task of the stomach is to empty its contents slowly into the small intestine.
The small intestine has 3 segments: the duodenum, the jejunum, and the ileum. Each part or section performs an important role in nutrient absorption. Production of Digestive Juices The glands that act first are in the mouth — the salivary glands. Absorption and Transport of Nutrients Digested molecules of food, as well as water and minerals from the diet, are absorbed from the cavity of the upper small intestine.
Carbohydrates It is recommended that about 55 to 60 percent of total daily calories be from carbohydrates. Protein Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. Fats Fat molecules are a rich source of energy for the body. Vitamins Another vital part of our food that is absorbed from the small intestine is the class of chemicals we call vitamins. How is the digestive process controlled?
Hormone Regulators A fascinating feature of the digestive system is that it contains its own regulators. The hormones that control digestion are gastrin, secretin, and cholecystokinin CCK : Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. It is also necessary for the normal growth of the lining of the stomach, small intestine, and colon.
Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. It stimulates the stomach to produce pepsin, an enzyme that digests protein, and it also stimulates the liver to produce bile. CCK causes the pancreas to grow and to produce the enzymes of pancreatic juice, and it causes the gallbladder to empty. Additional hormones in the digestive system regulate appetite: Ghrelin is produced in the stomach and upper intestine in the absence of food in the digestive system and stimulates appetite.
Peptide YY is produced in the GI tract in response to a meal in the system and inhibits appetite. Both of these hormones work on the brain to help regulate the intake of food for energy.
Nerve Regulators Two types of nerves help to control the action of the digestive system — extrinsic and intrinsic nerves. Share this page. Share on facebook. Share on twitter. Share on linkedin. Share on email. Share on print. Topics of this article. The slideshow shows how this happens:.
Food molecules in the small intestine are too large to pass across its wall and into the bloodstream. Carbohydrase enzymes in the small intestine begin to digest the food into smaller molecules. The food molecules are now small enough to move by diffusion through the wall of the small intestine into the bloodstream.
Absorption across a surface happens quickly and efficiently if:. The inner wall of the small intestine has adaptation so that substances pass across it quickly and efficiently:.
The stomach lining is unaffected by pepsin and the acidity because pepsin is released in an inactive form and the stomach has a thick mucus lining that protects the underlying tissue. Chyme moves from the stomach to the small intestine. The small intestine is the organ where the digestion of protein, fats, and carbohydrates is completed.
The small intestine is a long tube-like organ with a highly folded surface containing finger-like projections called the villi. The top surface of each villus has many microscopic projections called microvilli. The epithelial cells of these structures absorb nutrients from the digested food and release them to the bloodstream on the other side. The villi and microvilli, with their many folds, increase the surface area of the small intestine and increase absorption efficiency of the nutrients.
The human small intestine is over 6 m The duodenum is separated from the stomach by the pyloric sphincter. The chyme is mixed with pancreatic juices, an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme from the stomach. Pancreatic juices contain several digestive enzymes that break down starches, disaccharides, proteins, and fats. Bile is produced in the liver and stored and concentrated in the gallbladder; it enters the duodenum through the bile duct.
Bile contains bile salts, which make lipids accessible to the water-soluble enzymes. The monosaccharides, amino acids, bile salts, vitamins, and other nutrients are absorbed by the cells of the intestinal lining. The undigested food is sent to the colon from the ileum via peristaltic movements.
The ileum ends and the large intestine begins at the ileocecal valve. The appendix of humans has a minor role in immunity. The large intestine reabsorbs the water from indigestible food material and processes the waste material Figure The human large intestine is much smaller in length compared to the small intestine but larger in diameter.
It has three parts: the cecum, the colon, and the rectum. The cecum joins the ileum to the colon and is the receiving pouch for the waste matter. The colon has four regions, the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The main functions of the colon are to extract the water and mineral salts from undigested food, and to store waste material. The rectum Figure The feces are propelled using peristaltic movements during elimination.
The anus is an opening at the far-end of the digestive tract and is the exit point for the waste material. Two sphincters regulate the exit of feces, the inner sphincter is involuntary and the outer sphincter is voluntary. The organs discussed above are the organs of the digestive tract through which food passes. Accessory organs add secretions and enzymes that break down food into nutrients. Accessory organs include the salivary glands, the liver, the pancreas, and the gall bladder.
The secretions of the liver, pancreas, and gallbladder are regulated by hormones in response to food consumption. The liver is the largest internal organ in humans and it plays an important role in digestion of fats and detoxifying blood. The liver produces bile, a digestive juice that is required for the breakdown of fats in the duodenum. The liver also processes the absorbed vitamins and fatty acids and synthesizes many plasma proteins.
The gallbladder is a small organ that aids the liver by storing bile and concentrating bile salts. The pancreas secretes bicarbonate that neutralizes the acidic chyme and a variety of enzymes for the digestion of protein and carbohydrates. Nutrition The following video is primarily about water soluble vitamins such as vitamin B and C their roles, especially in energy metabolism. The liver makes bile , which helps the body absorb fat. Bile is stored in the gallbladder until it is needed.
The pancreas makes enzymes that help digest proteins, fats, and carbs. It also makes a substance that neutralizes stomach acid. These enzymes and bile travel through special pathways called ducts into the small intestine, where they help to break down food. The liver also helps process nutrients in the bloodstream. From the small intestine, undigested food and some water travels to the large intestine through a muscular ring or valve that prevents food from returning to the small intestine.
By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine's main job is to remove water from the undigested matter and form solid waste poop to be excreted. Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Is the Digestive System? Almost all animals have a tube-type digestive system in which food: enters the mouth passes through a long tube exits the body as feces poop through the anus Along the way, food is broken down into tiny molecules so that the body can absorb nutrients it needs: Protein must be broken down into amino acids.
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