Digestive Tract PDF

​digestive tract also called the alimentary canal Submucosa thick layer of loose connective tissue. It contains glands, blood vessels, lymphatic vessels, and nerves mechanical digestion Physical breakdown of large pieces of food into smaller pieces, beginning with chewing this is the first phase...

​digestive tract also called the alimentary canal Submucosa thick layer of loose connective tissue. It contains glands, blood vessels, lymphatic vessels, and nerves mechanical digestion Physical breakdown of large pieces of food into smaller pieces, beginning with chewing this is the first phase of digestion Mesenteries layers of visceral peritoneum, suspend the digestive organs within the abdominal cavity while anchoring them loosely to the abdominal wall Mouth also called buccal cavity, where digestion begins soft palate consists of mostly skeletal muscle Salivary glands secrete saliva- (a clear fluid consisting of mostly water) Mastication digestion begins when food enters the mouth and is chewed. Dentin the bulk of tooth consist of a firm, yellowish tissue; dentin and cementum can be regenerated Enamel cannot be regenerated Peristalsis Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system. Stomach A muscular and elastic sac that serves mainly to store food Chyme semifluid mixture, leaves the stomach and enters the duodenum intrinsic factor necessary for absorption of vitamin B12 cephalic phase sight, smell, taste or thought of food; stomach secretes gastric juices and gastrin liver body largest gland portal vein Carries oxygen-poor but nutrient-rich blood from the digestive organs and spleen to the liver sinusoids filter blood; allowing the cells to remove nutrients, hormones, toxins, and drugs gallbladder stores and concentrates bile Bilirubin body main bile pigment; results from breakdown of hemoglobin acinar cells secrete digestive enzymes in an inactive form small intestine most of the digestion and absorption of food occurs here duodenum most digestive processes occur here Trypsin chyme enters the duodenum, pepsin is inactivated Calorie the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius. the number of calories in food is a measure of the potential energy contained in that food Micronutrients vitamins and minerals obtaining essential amino acids get from plant source by combining a food deficient in one amino acid with another food containing that amino acid Ammonia so toxic that is a diseased liver fails to remove this nitrogenous waste product, coma and death will soon result when body temp rises too high the hypothalamus signals cutaneous blood vessels to dilate. More warm blood flows close to the body's surface and heat is lost through the skin. accessory organs teeth, tongue, salivary glands, liver, gallbladder, pancreas chief cells Secrete digestive enzymes, such as pepsinogen falciform ligament serves to anchor the liver to the abdominal wall Cholecystokinin (CCK) A hormone secreted by the small intestine (duodenum).forcing bile in the bile duct- and the release of pancreatic enzymes jejunum many large, closely spaced fold and millions of microscopic projections give the jejunum an enormous surface area, making it ideal location for nutrient absorption Peyer's patches clusters of lymphatic tissue ; scattered throughout the ileum carbohydrate digestion begins in the mouth with amylase protein digestion begins in the stomach with pepsin Pepsin hydrolyzes the peptide bonds between certain amino acids Chymotrypsin assume the task of breaking apart the peptide bonds peptidases brush border enzymes break the remaining chains onto individual amino acids that are absorbed in the bloodstream emulsification Breakdown of large fat into smaller droplets pancreatic lipase main fat-digesting enzyme that begins to digest the fat large intestine once food has been processed and nutrients absorbed, the remaining residue enters , which absorbs large amounts of water before passing the resulting waste material (feces) out of the body Metabolism nutrients enter cells and undergo chemical reactions, then transformed into energy or materials the body can use or store Body size and composition people who are larger or have more muscle mass burn more calories Gender Males tend to have less body fat and more muscle,they burn more calories Age muscle mass declines with age, slowing the metabolic rate Leptin suppresses appetite. Secreted by adipose tissue; signals the brain that the body has enough energy stores, and suppresses appetite. Levels are higher in people who are overweight. Obese people build up a resistance to the appetite suppressing effects. Ghrelin produces hunger Cholecystokinin suppresses appetite and is secreted by cells in the duodenum and jejunum Macronutrients carbohydrates, proteins, lipids, water carbohydrates body main primary energy source. most of the carbohydrates consumed should be complex carbohydrates bc these foods contain other vital nutrients in addition to carbohydrates Disaccharide broken down into monosaccharides, examples: sucrose, lactose, maltose Fat soluble vitamins stored in liver and fat tissues catabolism used in metabolism of carbohydrates and lipids this process breaks down complex substances into simpler ones or into energy nonessential amino acids body can synthesize 11 of its 12 amino acids, bc its not necessary to consume them through the diet lipids (fats) enable absorption of certain vitamins; contribute to cellular structure, insulate and protect the body, each gram of fat contains 9 calories per gram compared to 4 calories for each gram of carbohydrate. essential fatty acids The body can synthesize most fatty acids it needs, but there are a few it cannot synthesize protein During the process of digestion, proteins are broken down into their individual amino acids once absorbed the body recombines the amino acids to create a new protein for a specific purpose. complete proteins foods that supply all the essential amino acids, making them available at the same time incomplete proteins Foods that lack one or more essential amino acids carbohydrate metabolism all ingested carbohydrates are converted to glucose, most of which is immediately burned as energy. If the body doesn't need the glucose for immediate energy it stores it as glycogen or converts it to lipids. The primary goal of glucose catabolism is to generate ATP anaerobic fermentation occurs when oxygen is in short supply, pyruvic acid is converted into lactic acid. lactic acid travels to the liver for storage. When oxygen becomes available lactic acid is converted back into pyruvic acid, pyruvic acid then enters aerobic respiration aerobic respiration occurs when oxygen is available- this yields the most energy lipid metabolism produces more than twice as much energy as the breakdown of carbohydrates. when needed for energy, stored fat molecules in adipose tissue, hydrolyzed into glycerol + 3 fatty acid molecules protein metabolism protein may also be catabolized: converted to glucose and fat or used directly as fuel. Before that happens, the amino acids must be altered in the liver negative nitrogen balance the amount of nitrogen in the urine exceeds the amount of nitrogen in the protein foods ingested this happens when proteins are being catabolized more than being created - such as during starvation or a wasting illness Thermoregulation most of the body's heat results as a byproduct of the chemical reactions occurring in cells Conduction transfer of heat between two materials that touch each other