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Chapter 33 The Digestive System Medical Assisting
PowerPoint® presentation to accompany: Medical Assisting Third Edition Booth, Whicker, Wyman, Pugh, Thompson
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Learning Outcomes 33.1 List the functions of the digestive system.
33.2 Trace the pathway of food through the alimentary canal. 33.3 Describe the structure and functions of the mouth, teeth, tongue, and salivary glands. 33.4 Describe the structure and function of the pharynx.
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Learning Outcomes (cont.)
33.5 Describe the swallowing process. 33.6 Describe the structure of the esophagus and tell how it propels food into the stomach. 33.7 Describe the structure and functions of the stomach. 33.8 List the substances secreted by the stomach and give their functions.
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Learning Outcomes (cont.)
33.9 Describe the structure and functions of the small intestine. 33.10 List the substances secreted by the small intestine and describe the importance of each. 33.11 Describe the structure and functions of the large intestine, including the anal canal and rectum. 33.12 Explain the structures and functions of the liver, gallbladder, and pancreas.
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Learning Outcomes (cont.)
33.13 List the substances released by the liver, gallbladder, and pancreas into the small intestine and give the function of each secretion. 33.14 Tell what types of nutrients are absorbed by the digestive system and where they are absorbed. 33.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the digestive system.
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Introduction Digestion Two categories
Mechanical and chemical breakdown of foods into forms that body cells can absorb The organs of the digestive system carry out digestion Two categories Alimentary canal organs Accessory organs
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Characteristics of the Alimentary Canal
Wall of alimentary canal Mucosa Inner most layer; epithelial tissue Secretes enzymes and mucus into lumen Absorbs nutrients Submucosa Inferior to mucosa; loose connective tissue, blood vessels, glands, and nerves Blood vessels carries away absorbed nutrients Muscular layer Just outside submucosa; layers of smooth muscle Contracts to move materials through the canal
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Characteristics of the Alimentary Canal (cont.)
Serosa Double-walled outermost layer: peritoneum Visceral peritoneum Innermost wall of serosa Secretes serous fluid to keep outside of canal moist Parietal peritoneum Abdominal lining Movements Churning – mixes substances in the canal Peristalsis – propels substances through the tract
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Bravo! Apply Your Knowledge
What are the layers of the wall of the alimentary canal and what do they do? ANSWER: The layers are: Mucosa: innermost layer; secretes enzymes and mucus into the canal and absorbs nutrients Submucosa: inferior to the mucosa; carries away absorbed nutrients Muscular layer: just outside the submucosa; contracts to move materials through the canal Serosa: double-walled outer layer; secretes serous fluid to keep outside of canal moist Bravo!
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The Mouth Buccal cavity Mechanical digestion Starts chemical digestion
Takes in food and reduces its size by chewing Starts chemical digestion Saliva contains enzyme amylase, which breaks down carbohydrates
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The Mouth (cont.) Cheeks hold food in mouth
Lips – sensory nerve fibers that judge temperature of food Tongue Skeletal muscles covered by mucous membrane Lingual frenulum – holds tongue to floor of mouth Mixes food, holds food between teeth, contains taste buds Lingual tonsils – lymphatic tissue destroys bacteria and viruses on back of tongue
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The Mouth (cont.) Palate Lymph tissue Roof of mouth
Separates oral cavity from nasal cavity Uvula – portion of soft palate that hangs down in throat Lymph tissue Palatine tonsils (oropharynx) Pharyngeal tonsils – adenoids (nasopharynx)
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The Mouth (cont.) Teeth – decrease size of food particles
Incisors – bite off food pieces Cuspids – tear tough food Bicuspids and molars – grind food Salivary glands Cells Serous Mucous Glands Parotid Submandibular Sublingual
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Apply Your Knowledge Very Good! Matching: ___ Buccal cavity A. Saliva
___ Roof of mouth B. Mouth ___ Grind food C. Bolus ___ Adenoids D. Palate ___ Water, enzymes, and mucus E. Bicuspids ___ Mass of food mixed with saliva and mucus F. Pharyngeal gland B ANSWER: D Very Good! E F A B
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Pharynx Throat Functions Divisions Nasopharynx
Connects nasal cavity with oral cavity for breathing Pushes food into esophagus Divisions Nasopharynx Behind nasal cavity Oropharynx Behind oral cavity Laryngopharynx Behind larynx Continues as esophagus
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Pharynx (cont.) Swallowing – automatic process
Soft palate raises, uvula covers opening between nasal and oral cavity Epiglottis covers larynx, keeping food out of it Tongue presses against roof of mouth, forcing food into oropharynx
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Pharynx (cont.) Muscles in pharynx contract, moving food toward esophagus Esophagus opens Food is pushed into esophagus by muscles of pharynx
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The Esophagus Muscular tube connecting pharynx to stomach
Esophageal hiatus – hole in diaphragm through which esophagus passes Cardiac sphincter Circular band of muscle at the opening of the stomach controls movement of food into stomach
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Apply Your Knowledge CORRECT! ANSWER: E D B A C Matching:
___ Connects nasal cavity with oral cavity A. Cardiac sphincter ___ Covers the opening of larynx B. Esophageal hiatus ___ Hole in diaphragm C. Sphincter ___ Controls movement of food into stomach D. Epiglottis ___ Circular bands of muscle E. Pharynx ANSWER: E D B A C CORRECT!
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The Stomach Sections Pyloric sphincter
Below the diaphragm in the upper left quadrant of the abdominal cavity Functions Receive food from esophagus Mix bolus with gastric juice Start protein digestion Move food into small intestine Sections Cardiac region Fundus Body Pylorus Pyloric sphincter Controls movement of substances into small intestine Stomach
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The Stomach (cont.) Lining of stomach
Rugae – folds of the inner lining Gastric glands Mucous cells – secrete mucus to protect the lining Chief cells – secrete pepsinogen pepsin, which digests protein Parietal cells Hydrochloric acid needed to convert pepsinogen to pepsin Intrinsic factor needed for vitamin B12 absorption Stomach
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Back
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The Stomach (cont.) Gastric glands stimulated by
Parasympathetic nervous system Gastrin (hormone) Cholesystokinin (hormone) secreted by the small intestine inhibits gastric glands Stomach absorbs alcohol, water, and some fat-soluble drugs Chyme – mixture of food and gastric juices
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Right Answer! Apply Your Knowledge
What are the functions of the stomach? ANSWER: The stomach’s functions are to receive the bolus of food, mix it with gastric juice, start protein digestion, and move food into the small intestine. It also absorbs alcohol, water, and some drugs. Right Answer!
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The Small Intestine Duodenum Jejunum
Tubular organ extending from the stomach to the large intestine Functions Digestion Absorption of nutrients Duodenum C-shaped Short Jejunum Coiled Majority of small intestine Small Intestine
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The Small Intestine Ileum Mesentery Ileocecal sphincter
Attached to large intestine Mesentery Fan-like tissue that holds jejunum and ileum in the abdominal cavity Attaches to the posterior wall of the abdomen Ileocecal sphincter Controls movement of chyme from the ileum to the cecum of the large intestine Small Intestine
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The Small Intestine (cont.)
Lining of small intestine Microvilli – increase surface area Intestinal glands Mucus and water Enzymes Peptidases – digest proteins Sucrase, maltase, and lactase – digest sugars Intestinal lipase – digests fats Primary controls Parasympathetic nervous system Stretching of intestinal wall
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Back
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Apply Your Knowledge Nice Job!
Your patient states that she is lactose intolerant. What does that mean? ANSWER: She cannot produce lactase and cannot digest lactose, which is the sugar in dairy products. Nice Job!
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The Large Intestine Extends from the ileum to the anus Cecum
Beginning of large intestine Veriform appendix Ascending colon Portion that goes up the right side of the abdominal cavity Large Intestine
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The Large Intestine (cont.)
Transverse colon Crosses abdominal cavity from right to left Descending colon Down left side of abdominal cavity Sigmoid colon S-shaped portion in pelvic cavity Absorbs water and electrolytes Large Intestine
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The Rectum and Anal Canal
Rectum – off sigmoid colon Anal canal Last few centimeters of rectum Opening to outside of body is the anus Large Intestine
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The Rectum and Anal Canal
Feces Leftover chyme Consists of undigested solid materials, little water, ions, mucus, cells of intestinal lining, and bacteria Defecation reflex Triggered by periodic contractions of large intestine Allows anal sphincters to relax
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Back
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Super! Apply Your Knowledge ANSWER: Matching:
___ Vermiform appendix A. Feces ___ Crosses the abdomen B. Ascending colon ___ Up right side of abdomen C. Anal canal ___ S-shaped tube D. Defecation reflex ___ Down left side of abdomen E. Sigmoid ___ Leftover chyme F. Transverse colon ___ Last section of rectum G. Cecum ___ Allows anal sphincters to relax H. Descending colon ANSWER: G F B E H A C D
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The Liver Lobular organ in right upper quadrant
Large right lobe and smaller left lobe Hepatic lobules – contain macrophages Hepatocytes – process nutrients in blood and make bile Part of liver’s function Store vitamins and iron
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The Liver (cont.) Hepatic portal vein – carries blood from digestive organs to hepatic lobules Hepatic duct – bile from liver Hepatic duct merges with cystic duct from gallbladder and forms common bile duct Common bile duct – delivers bile to duodenum
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The Gallbladder Small sac-like structure located beneath the liver
Only function is to store bile Cholecystokinin causes the gallbladder to release bile Gallbladder
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Apply Your Knowledge Excellent!
What is the route of bile through the liver and gall bladder? ANSWER: Bile is made in the hepatocytes and leaves the liver through the hepatic duct. The hepatic duct merges with the cystic duct from the gall bladder to form the common bile duct, which delivers bile to the duodenum. Excellent!
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The Pancreas Located behind the stomach
Acinar cells produce pancreatic juice, which contains these enzymes: Pancreatic amylase – digests carbohydrates Pancreatic lipase – digests lipids Nucleases – digests nucleic acids Trypsin, chymotrypsin, and carboxypeptidase – digest proteins
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The Pancreas (cont.) Also secretes bicarbonate ions into duodenum
Neutralize acidic chyme Enzyme release stimulated by Parasympathetic nervous system Hormones secretin and cholecystokinin (from small intestine)
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Good Job! Apply Your Knowledge
What are the pancreatic enzymes and what do they do? ANSWER: They are: Pancreatic amylase – digests carbohydrates Pancreatic lipase – digests lipids Nucleases – digest nucleic acids Trypsin, chymotrypsin, and carboxypeptidase – digest proteins Good Job!
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The Absorption of Nutrients
Nutrients are necessary food substances Carbohydrates Proteins Lipids Vitamins Minerals Water
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The Absorption of Nutrients (cont.)
Carbohydrates – provide energy Polysaccharides – starches Monosaccharides and disaccharides – simple sugars Cellulose – provides fiber or bulk Lipids – used for energy when glucose levels are low Triglycerides Cholesterol – essential for cell growth and function
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The Absorption of Nutrients (cont.)
Protein – used for growth and repair of tissue Essential amino acids body can not make Vitamins Fat-soluble Water-soluble Minerals – used to make enzymes, cell membranes, and proteins
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Apply Your Knowledge Impressive! True or False:
___ Carbohydrates are starches, simple sugars, and cellulose. ___ Excess glucose is stored in the gallbladder as glycogen. ___ Triglycerides are the least abundant lipids ___ Linoleic acid is an essential fatty acid. ___ A, D, E and K are water-soluble vitamins. ___ Minerals are used by cells to make enzymes. ANSWER: T liver F most F T Impressive! F fat-soluble T
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Aging and the Digestive System
Decreased motility – GERD Decreased absorption More likely to develop ulcers and cancers Decreased ability to detoxify blood Sense of taste altered Dietary changes due to Isolation Depression
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Common Diseases and Disorders
Disease / Disorder Description Appendicitis Inflammation of the appendix; can be life-threatening if not treated promptly Cirrhosis Chronic liver disease; normal tissue is replaced with nonfunctional scar tissue Colitis Inflammation of the large intestine; can be acute or chronic Colorectal cancer Arises from lining of rectum or colon; curable if treated early
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Common Diseases and Disorders (cont.)
Disease / Disorder Description Constipation Difficult defecation Crohn’s disease Inflammatory bowel disease; typically effects small intestine Diarrhea Watery and frequent feces; usually self-limiting Diverticulosis Abnormal pouches in the intestinal wall; no inflammation present
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Common Diseases and Disorders (cont.)
Disease / Disorder Description Diverticulitis Inflammation of diverticuli (abnormal pouches in intestinal wall) of the intestine Gastritis Inflammation of the stomach lining; “upset stomach” Heartburn Gastroesophageal reflux disease (GERD); stomach acids push into esophagus Hemorrhoids Varicose veins of rectum or anus Hepatitis Inflammation of the liver; various types
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Common Diseases and Disorders (cont.)
Disease / Disorder Description Hiatal hernia Portion of stomach protrudes into the chest through an opening (usually the esophageal hiatus) in the diaphragm Inguinal hernia Portion of large intestine protrudes in the inguinal canal (where thigh and trunk meet) or, in males, into the scrotum Oral cancer Usually involves the lips or tongue but can occur anywhere in the mouth; tends to spread rapidly
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Common Diseases and Disorders (cont.)
Disease / Disorder Description Pancreatic cancer Fourth leading cause of cancer deaths in the U.S. Stomach cancer Commonly in cardiac portion of the stomach; occurs more frequently in Japan, Chili, and Iceland Stomach ulcers Breakdown in lining of the stomach; can be caused by bacteria (H. pylori) or smoking, alcohol, excessive aspirin use, and hypersecretion of stomach acid
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Apply Your Knowledge Nice Job! ANSWER: E Matching:
___ Inflammation of the large intestine A. Heartburn ___ Inflammatory bowel disease B. Hemorrhoids ___ Watery and frequent feces C. Constipation ___ Difficult defecation D. Chron’s disease ___ Inflammation of the stomach lining E. Colitis ___ Inflammation of pouches in the intestinal wall F. Diarrhea ___ GERD G. Gastritis ___ Varicose veins of rectum H. Diverticulitis D F C G H A B Nice Job!
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In Summary Purpose of the digestive system is to provide nutrients to the body Organs of alimentary canal are responsible for mechanical and chemical breakdown of food Accessory organs Assist in breakdown of food Eliminate waste Medical assistant must have knowledge of this system Assist with procedures Patient education
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End of Chapter End of Chapter 33 Take all that is given whether wealth, love or language; nothing comes by mistake and with good digestion all can be turned to health. ~ George Herbert
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