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Digestive System HCT II Objectives Label the pharynx, esophagus, stomach and small intestines Explain the function of these digestive organs Explain how food is absorbed into the body by the villi in the small intestine Describe how gastric juices act on food in the stomach Pharynx (throat) After food becomes bolus it enters the throat This carries both air and food. Carries air to the trachea Carries food to the esophagus Esophagus Muscular tube dorsal (behind) the trachea Receives bolus from the pharynx and carries it to the stomach Relies on Peristalsis (rhythmic involuntary wavelike movements) of its muscles to move food in a forward direction Stomach Enlarged part of the alimentary canal Receives food from the esophagus Lined with a mucus membrane containing folds called rugae that disappear as the stomach expands Cardiac Sphincter Circular muscle between the esophagus and stomach Closes after food enters the stomach’ Prevents food from going back up into the esophagus What is it called when food goes back up into the esophagus? Reflux Pyloric Sphincter Circular muscle between the stomach and the small intestine Keeps food in the stomach until it is ready to enter the small intestine How many hours does food usually stay in the stomach? 1-4 hours Gastric Juices Produced by glands in the stomach Converts food into a semifluid material called chyme Juices contain HCL Kill bacteria Facilitates the absorption of iron Activates the enzyme pepsin Juices also contain Lipase- begins the chemical breakdown of fats Pepsin- starts protein digestion Enzyme rennin- in infants only (aids in the digestion of milk) Small Intestine Coiled section of the alimentary canal about 20 feet long and 1 inch in diameter NOT SO SMALL!!! Receives food in the form of chyme from the stomach. Small intestine Three sections Duodenum Jejunum First 9- 10 inches Bile from the liver, gallbladder and pancreatic juices enter this section through ducts or tubes About 8 feet long (the middle section) Ileum Final 12 feet Connects with the large intestine at the cecum Circular muscle called the ileocecal valve prevents food from returning to the ilium Functions of the small intestine Completes digestion Absorbs the products of digestion into the blood stream for use by our cells Intestinal Juices Produced by the small intestine Contain enzymes which break down sugars Maltase Sucrase lactase Also contains the enzyme peptidases, which completes digestion of proteins. Bile liquid from the liver and gallbladder Emulsifies or breaks down fats Why can fatty diets lead to gallbladder disease? Pancreatic Juices Liquid that enters the small intestine from the pancreas Contains enzymes that complete the process of digestion Amylase- acts on sugar Trypsin and chymotrypsin- act on proteins Lipase- acts on fats Villi Fingerlike projections lining the walls of the small intestine Allow food to be absorbed and taken into the bloodstream Blood capillaries Absorb digested nutrients Carry to the liver for storage Release nutrients into the general circulation for use. Lacteals-pick up digested fats and carry them to the thoracic duct Where does the thoracic duct take them to? *** when food has completely passed through the small intestine only wastes, water and indigestible materials remain.
