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The Alimentary Canal - the one way passageway for food / nutrients / waste Human Alimentary Canal • • • • • • Mouth Pharynx Esophagus Stomach Small intestine Large intestine Mouth • True digestive organ • physical & chemical digestion • Salivary Amylase breaks carbohydrates into disaccharides/maltose • contains teeth, tongue, soft & hard palate to help with physical digestion • food is ingested Salivary Glands • Accessory Organs • produce salivary amylase – sublingual – submandibular – parotids Pharynx aka. The throat • True digestive organ • no physical or chemical digestion occurs here • hooks in with the respiratory system Esophagus • True digestive organ • no physical or chemical digestion occurs here • food considered a BOLUS wet ball of chewed food • PERISTALSIS starts here wavelike contractions of the tube that moves the foodstuff along the alimentary canal Stomach • Very muscular organ that participates in both physical & chemical digestion • true digestive organ • lined with thick protective mucous • the enzyme pepsinogen activates in the acid conditions in the stomach and becomes pepsin • pepsin digests the proteins into groups of 2 amino acids • cardiac sphincter valve is at the top and the pyloric valve is between the stomach & small intestine • the bolus is now considered chyme Small Intestine • True digestive organ • chemical digestion is completed here • contains 3 main portions – duodenum first 10 cm of small intestine – jejunum next 2 ½ meters – ileum last 4 meters •the role of the small intestine is threefold 1. Finish digestion 2. Absorb nutrients 3. Storage •contains villi for absorption of nutrients Small Intestine Enzyme Action • Common bile duct hooks into duodenum • this hooks up to the pancreas and gallbladder • pancreatic juice & bile is secreted is secreted through this • BILE & bile salts- emulsifies the fat breaks into smaller droplets • Pancreatic Juice contains: – sodium bicarbonate / to neutralize the acid from the stomach – lipase / breaks fats into fatty acids & glycerol – trypsinogen in changed into trypsin in the si. Environment and digests the dipeptides into single amino acids – pancreatic amylase finishes carbohydrate digestion by breaking disaccharides into monosacharides • Increases the surface area in the small intestine for the maximum nutrient absorption • monosaccharides & amino acids are diffused into the capillaries bloodstream • fatty acids & glycerol are absorbed by the lacteal which hooks into the lymphatic system Villi Pancreas • Accessory digestive organ • produces pancreatic juice which contains pancreatic amylase, sodium bicarbonate, trypsinogen and lipase • located under the stomach • LIVER – produces bile which breaks up the larger fats • GALLBLADDER – stores the bile until needed Large Intestine • True digestive organ, but digestion is all done by now!!! • The function is to absorb water & minerals • at the junction of the small & large intestine is the appendix • there are 5 portions of the large intestine – – – – – ascending colon transverse colon descending colon sigmoid colon rectum which ends in the anal sphincter methane in is a normal bi-product and in combination with e. coli bacteria produce flatulence • At this point the waste products are referred to as feces • CONSTIPATION - waste sits in large intestine too long and the stool becomes too hard and is difficult to evacuate • DIARRHEA - waste does not sit in the large intestine long enough and not enough water is absorbed producing a watery stool Hormones of the Digestive System • GASTRIN – cells of the stomach secrete into bloodstream – triggers cells of stomach to secrete hydrochloric acid so pepsinogen converts to pepsin • SECRETIN – when food enters the small intestine – secreted by the cells of si. Into the bloodstream – triggers pancreas to make pancreatic juice