Digestive System Ch. 14

Digestive System The digestive system has a simple job, gather nutrients. The digestive system has a simple job, gather nutrients. There are two divisions: There are two divisions: Alimentary – Ingests, digests, absorbs, defecates (stomach, intestine, etc) aka gastrointestinal tract Alimentary – Ingests, digests, absorbs, defecates (stomach, intestine, etc) aka gastrointestinal tract Accessory – helps the alimentary organs complete their goal. (teeth, pancreas, etc) Accessory – helps the alimentary organs complete their goal. (teeth, pancreas, etc)

Gastrointestinal Tract A twisty, hollow tube that runs continuously from the mouth to the anus. A twisty, hollow tube that runs continuously from the mouth to the anus. It is divided into sections, each with a specific purpose. It is divided into sections, each with a specific purpose. Includes: Mouth, pharynx, esophagus, stomach, sm. Intestine, and lg. Intestine. Includes: Mouth, pharynx, esophagus, stomach, sm. Intestine, and lg. Intestine. The terminal opening is the anus. The terminal opening is the anus.

Mouth Lips protect anterior Lips protect anterior Cheeks form lateral walls Cheeks form lateral walls Hard and soft palate form roof Hard and soft palate form roof Muscular tongue occupies the floor of the oral cavity. Muscular tongue occupies the floor of the oral cavity. Tongue attached to the bottom of the mouth by the lingual frenulum. Tongue attached to the bottom of the mouth by the lingual frenulum.

Mouth The area between your cheeks/lips and your teeth is called the vestibule. The area behind your teeth is the oral cavity proper. The area between your cheeks/lips and your teeth is called the vestibule. The area behind your teeth is the oral cavity proper. Two sets of tonsils – palatine in the back, lingual cover the back of the tongue just further along. When inflamed, it hurts to swallow. Two sets of tonsils – palatine in the back, lingual cover the back of the tongue just further along. When inflamed, it hurts to swallow.

Mouth Mastication – food in the mouth is chewed using teeth to break it down (give it more surface area) Mastication – food in the mouth is chewed using teeth to break it down (give it more surface area) Salivary glands produce saliva with amylase in it. The tongue mixes the food around like a washing machine. Salivary glands produce saliva with amylase in it. The tongue mixes the food around like a washing machine.

Teeth Teeth are used to rip and grind food into small bits. Teeth are used to rip and grind food into small bits. From birth – 2yr our milk teeth grow in, 20 total. From birth – 2yr our milk teeth grow in, 20 total. From 7yr – 25yr our second set (permanent) of teeth grow in. From 7yr – 25yr our second set (permanent) of teeth grow in. Full set is 32. This number changes based on impaction and wisdom teeth. Full set is 32. This number changes based on impaction and wisdom teeth.

Teeth Teeth are named based on their shape. Teeth are named based on their shape. Incisors for cutting Incisors for cutting canines for piercing and ripping canines for piercing and ripping premolars and molars for grinding. premolars and molars for grinding.

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Tooth Teeth have two major areas, the crown and the root. Teeth have two major areas, the crown and the root. The crown is covered in enamel – hardest substance in the body and heavily mineralized with calcium. The crown is covered in enamel – hardest substance in the body and heavily mineralized with calcium. Gums or gingiva bridge the gap between teeth. Gums or gingiva bridge the gap between teeth.

Tooth Below the gum line is the root. Held in place by the periodontal membrane and the cementum. Below the gum line is the root. Held in place by the periodontal membrane and the cementum. Internally, the tooth is made up of dentin, a bone like material and the pulp. Internally, the tooth is made up of dentin, a bone like material and the pulp.

Tooth The pulp is a central cavity filled with connective tissue, blood vessels and nerve fibers. The pulp is a central cavity filled with connective tissue, blood vessels and nerve fibers. Cavities eat away enamel, making the tooth weaker. If the decomposition gets too deep near the pulp, a root canal is performed. Cavities eat away enamel, making the tooth weaker. If the decomposition gets too deep near the pulp, a root canal is performed.

Pharynx After the mouth, food enters the “throat” or pharynx. After the mouth, food enters the “throat” or pharynx. The walls of the pharynx contain two skeletal muscle layers which begin peristalsis (more later). The walls of the pharynx contain two skeletal muscle layers which begin peristalsis (more later).

Esophagus 10” tube that connects the throat to the stomach 10” tube that connects the throat to the stomach Made of four layers (tunica) Made of four layers (tunica) Mucosa – innermost, lines the lumen, surface epithelium and smooth muscle. Friction-resisting. Mucosa – innermost, lines the lumen, surface epithelium and smooth muscle. Friction-resisting. Submucosa – soft connective tissue with blood vessesls, nerves, lymph vessels and nodes. Submucosa – soft connective tissue with blood vessesls, nerves, lymph vessels and nodes. Muscularis Externa – Muscles for Peristalsis Muscularis Externa – Muscles for Peristalsis Serosa – serous fluid producing. Part of the continuous visceral peritoneum that lines the abdominopelvic cavity, including mesentary. Serosa – serous fluid producing. Part of the continuous visceral peritoneum that lines the abdominopelvic cavity, including mesentary.

Stomach On the left side of the abdominal cavity. On the left side of the abdominal cavity. Approximately 10” long, diameter changes as food fills it. Approximately 10” long, diameter changes as food fills it. Can hold approximately 1 gallon of food Can hold approximately 1 gallon of food Separated from the esophagus by the cardioesophageal sphincter and separated from the Sm. Intestine by the Pyloric Sphincter. Separated from the esophagus by the cardioesophageal sphincter and separated from the Sm. Intestine by the Pyloric Sphincter.

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Stomach Stomach has three layers of muscles, running longitudinally, transversely, and obliquely. These three layers contract in rhythm to constantly churn and pummel the food. Stomach has three layers of muscles, running longitudinally, transversely, and obliquely. These three layers contract in rhythm to constantly churn and pummel the food. Proteins begin to be broken down here by gastric juice. Proteins begin to be broken down here by gastric juice. Food stays here until it is the consistency of a heavy cream. Called chyme. Food stays here until it is the consistency of a heavy cream. Called chyme.

Activity of the Stomach Produces Pepsin – enzyme that breaks down protein. Produces Pepsin – enzyme that breaks down protein. Pepsin requires an acidic environment, stomach also produces hydrochloric acid. Pepsin requires an acidic environment, stomach also produces hydrochloric acid. Stomach tissue is protected from this acid by mucus. If no mucus, the stomach could eat itself called an ulcer. Stomach tissue is protected from this acid by mucus. If no mucus, the stomach could eat itself called an ulcer. Stomach muscles constantly mix food with acid. Stomach muscles constantly mix food with acid. Once liquefied, Chyme, food enters the sm. Intestine via the pyloric sphincter. Once liquefied, Chyme, food enters the sm. Intestine via the pyloric sphincter.

Small Intestine The major digestive organ. The major digestive organ. 7 meters long 7 meters long Can only process a small amount at a time, kept in stomach. Can only process a small amount at a time, kept in stomach. Three subdivisions Three subdivisions Duodenum Duodenum Jejunum Jejunum Ileum Ileum

Duodenum The first and smallest section. Starts at the end of the stomach, turns down and then transverse. Makes a C Shape. The first and smallest section. Starts at the end of the stomach, turns down and then transverse. Makes a C Shape. Pancreatic duct empties here, releasing pancreatic digestive enzymes. Pancreatic duct empties here, releasing pancreatic digestive enzymes. Bile duct from liver also empties into the duodenum. Bile duct from liver also empties into the duodenum.

Activities of the Small Intestine The pancreas and gall bladder empty their contents into the small intestine. This releases enzymes and neutralizes the chyme back to about pH 8 The pancreas and gall bladder empty their contents into the small intestine. This releases enzymes and neutralizes the chyme back to about pH 8 Enzymes Enzymes Pancreatic amylase, lactase, maltase and sucrase finish the breakdown of carbs that was started in the mouth Pancreatic amylase, lactase, maltase and sucrase finish the breakdown of carbs that was started in the mouth Trypsin continues the breakdown of proteins Trypsin continues the breakdown of proteins Bile and pancreatic lipase begin to breakdown fats Bile and pancreatic lipase begin to breakdown fats

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Sm. Intestine Nearly all food absorption occurs in the sm. Intestine. Nearly all food absorption occurs in the sm. Intestine. A large amount of surface area is produced because the inside layer of the sm. Intestine is highly folded (circular folds). These folds have villi on them which are made up of cells with microvilli. All of which make more surface area for absorption. A large amount of surface area is produced because the inside layer of the sm. Intestine is highly folded (circular folds). These folds have villi on them which are made up of cells with microvilli. All of which make more surface area for absorption.

Activities of the Small Intestine As chyme is constantly digested by these various enzymes, nutrients are absorbed by microvilli of the intestinal walls. As chyme is constantly digested by these various enzymes, nutrients are absorbed by microvilli of the intestinal walls. These nutrients are routed into the hepatatic portal vein. These nutrients are routed into the hepatatic portal vein. They are taken to the liver for detoxification before being emptied into the blood stream. They are taken to the liver for detoxification before being emptied into the blood stream. Chyme left in the small intestine is pushed through by peristalsis. Chyme left in the small intestine is pushed through by peristalsis.

Large Intestine Its name refers to its diameter, not its length (5ft) Its name refers to its diameter, not its length (5ft) It extends from the ileocecal valve of the sm. Intestine to the anus. It extends from the ileocecal valve of the sm. Intestine to the anus. Major function is to dry out the indigestible food residue by absorbing water and to eliminate the residue from the body as feces. Major function is to dry out the indigestible food residue by absorbing water and to eliminate the residue from the body as feces. Sections: cecum, appendix, colon, rectum, and anal canal. Sections: cecum, appendix, colon, rectum, and anal canal.

Activities of the Large Intestine Chyme in the Lg. Intestine has very few nutrients. Chyme in the Lg. Intestine has very few nutrients. Bacteria living in the lumen can breakdown the chyme releasing a few vitamins, but not much. Bacteria living in the lumen can breakdown the chyme releasing a few vitamins, but not much. The liquid is absorbed by the lg. intestine, this makes the feces more solid. The liquid is absorbed by the lg. intestine, this makes the feces more solid.

Accessory Digestive Organs Salivary Glands – make saliva – mucus and serous fluids. Mucus moistens and binds the food into a mass called the bolus. Salivary Glands – make saliva – mucus and serous fluids. Mucus moistens and binds the food into a mass called the bolus. Serous fluid contains enzymes amylase to break down carbs. Also contains lysozyme and antibodies to inhibit bacteria. Serous fluid contains enzymes amylase to break down carbs. Also contains lysozyme and antibodies to inhibit bacteria.

Accessory Digestive Organs Teeth Teeth Pancreas – produces enzymes and alkaline fluid to break down food and neutralize acidic chyme. Pancreas – produces enzymes and alkaline fluid to break down food and neutralize acidic chyme. Liver – produces many enzymes, digestively, bile. Emulsifies fats Liver – produces many enzymes, digestively, bile. Emulsifies fats Gallbladder – stores bile when digestion is not occuring. Gallbladder – stores bile when digestion is not occuring.

Six Steps of Digestion Ingestion Ingestion Propulsion Propulsion Mechanical Breakdown Mechanical Breakdown Chemical Breakdown Chemical Breakdown Absorption Absorption Defecation Defecation