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The Digestive System S Digestive System S The Digestive System is responsible for the mechanical and chemical break down of food so it can be taken in to the blood stream and used by body cells and tissues. S Digestion begins in the mouth with the mechanical break down of food and ends in the large intestine with absorption Alimentary Canal S Long muscular tube S Begins at the mouth and ends at the anus S Accessory organs: salivary glands, tongue, teeth, liver, gallbladder, pancreas Digestive System A collection of structures that work together to break down food for nutrients and energy Mouth, Buccal, or Oral Cavity S Receives food as it enters the body S Actions in the mouth S Teeth: break down food by grinding it down S Tongue: allows for taste, and aids with chewing and swallowing S Hard palate: separates mouth from nasal cavity S Soft palate: has uvula which blocks food from entering the nasopharynx Mouth or Buccal Cavity S Saliva Purpose: S Salivary Glands: S 3 pairs of glands: S Parotid, sublingual, and submadibular S Produces saliva S Lubricates the mouth during speech and chewing S Moistens food so it can be swallowed easily S Also contains enzyme that speeds up the chemical breakdown of carbohydrates or starches Pharynx or Throat S Carrier for both air and food S Carries food bolus to the esophagus S When bolus swallowed, epiglottis closes to prevent food from entering respiratory tract Esophagus S Muscular tube dorsal to the trachea S Carries bolus to stomach S Peristalsis moves food toward stomach S Peristalsis is rhythmic, wavelike involuntary movement of it’s muscles Stomach S Receives food from esophagus S Mucous membrane lining contains rugae S Cardiac sphincter: small muscle that keeps food from returning to esophogus S Pyloric sphincter: small muscle that keeps food from entering small intestine until the appropriate time S Food remains in stomach about 2– 4 hours Stomach S Gastric Juices: S Juices contain enzymes: S Produced by glands in the S Lipase: breaks down fat stomach S Converts food into semifluid material called chyme S Juices contain hydrochloric acid that kills bacteria, facilitates absorption of iron, and activates pepsin S Pepsin: breaks down protein S In infants contains renin that helps to digest milk S Not present in adults Small Intestine S About 20 feet long; 1 inch in diameter S Receives food from the stomach in the form of chyme from stomach S Small intestine S Duodenum: first 9-10 inches, receives bile from gall bladder and liver, and pancreatic juice from pancreas S Jejunum: Middle 8 feet S Ileum: final 12 feet, connects with large intestine Small Intestine S Absorbs products of digestion into blood stream for cells to use S Intestinal juices: series of enzymes that break down sugars and proteins S Bile: Comes from gall bladder and liver to emulsify and break down fats S Pancreatic juice: Contains the enzymes that complete digestion of sugars, lipids, and proteins S Villi: Contain blood capillaries that absorb the nutrients in to the blood stream S Villi also have lacteals that pick up fats and carry them to thoracic duct in the lymphatic system, which releases them in to the circulatory system S When food has finished its journey through the small intestine, only wastes, indigestible materials, and excess water remain Large Intestine S About 5 feet long; 2 inches in diameter S Functions: S Absorb water and remaining nutrients S Storage of indigestible waste to be eliminated S Transportation of waste S Absorption and production of vitamin B complex and vitamin K Large Intestine S 3 parts: S Cecum: first section S Connects with small intestine S Contains appendix S Transverse Colon S Descending Colon S Sigmoid Colon: attaches to the rectum S Colon: 3 parts S Rectum: Final 6-8 inches S Ascending colon S Stores waste S Has a narrow canal called the anus, where waste exits body Liver S Largest gland in the body S Accessory organ for digestive system S Location: upper right quadrant Liver Functions S Secretes Bile: emulsify fat and physically breaks down fats S Makes fats water soluable S Stores Iron and certain vitamins S Produces heparin which prevents clotting S Stores sugar in the form of S S Releases sugar in blood stream S Produces cholesterol glycogen: which is converted to glucose when sugar is needed Produces fibrinogen and prothrombin which aids in clotting of blood S Detoxifies substances like alcohol, pesticides, and destroys bacteria Gallbladder S Small muscular sac S Location: under the liver S Stores and concentrates bile S Bile needed to emulsify fats Pancreas S Fish-shaped organ located behind the stomach S Produces pancreatic juices to digest food S Produces insulin which is secreted into the blood stream; regulates burning of carbohydrates to convert glucose to energy Pancreas