How long is the gastrointestinal tract? 9 m (29 ft) long Foods are digested in and absorbed from the gastrointestinal tract. Metabolism: products of digestion are metabolized in the cells of the body.
Location of digestive organs.
What is the function of the uvula? It prevents food from entering the nasal cavities. What is the lingual frenulum? A thin membrane that attaches the tongue to the floor of the mouth What happens when the frenulum is too short? Free movements of the tongue is severely restricted; individuals with this condition cannot enunciate words normally and are said to be “tongue-tied.” See Figure 17-2. Discuss therapies for this condition. Surgery, speech therapy
Mouth cavity and tongue. A, Mouth cavity showing hard and soft palates, tongue surface, and uvula. B, Undersurface of tongue showing frenulum, sublingual gland, and opening of sublingual duct. C, Photograph shows an abnormally short lingual frenulum, which may result in faulty speech. D, Papillae with taste buds located on the lateral surfaces. (C, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 5, Philadelphia, 2007, Mosby., D, Dennis Strete.)
What is the major function of the bicuspids and tricuspids? They begin the mechanical breakdown of food by chewing. How are they structurally suited to performing this function? They have large surfaces with several grinding or crushing sharp points on the surface. Crown: visible part of tooth. What covers the outside of the tooth? Enamel What is the neck of the tooth? The portion in direct contact with the gums Root: holds the tooth in the socket, which is lined with a fibrous periodontal membrane and is connected to the pulp, which is the central-most part of the tooth. What important structures are found in the pulp? Nerves, blood and lymphatic vessels Why does a dentist anesthetize the patient when drilling a tooth? In the process of drilling out the decayed part of a tooth, the drill tip may enter the pulp cavity of the tooth, which contains sensory nerves. Discuss the importance of the baby teeth in maintaining the health of the permanent teeth. Healthy teeth are important for good nutrition. When are baby teeth formed, as opposed to when they erupt? Tooth buds are formed prenatally. What is gum disease, and why is it significant? Gum disease, or gingivitis, is inflammation or infection of the guns. Most cases result from poor oral hygiene – inadequate brushing and/or flossing. Gingivitis is the leading cause of adult tooth loss. Why do heart patients and diabetics take prophylactic antibiotics before a dental visit? Gingivitis may be a complication of diabetes mellitus, vitamin deficiency, or pregnancy. Patients with cardiac disease or diabetes mellitus should try to avoid infections. Any dental procedure may dislodge bacteria around the gum tissue and thereby facilitate its transport to other parts of the body.
The deciduous (primary) teeth and adult teeth. In the deciduous (primary) set, also called “baby” teeth, there are no premolars and only two pairs of molars in each jaw. Generally the lower teeth erupt before the corresponding upper teeth. (Barbara Cousins.)
Longitudinal section of a tooth. A molar is sectioned here to show its bony socket and details of its three main parts: crown, neck, and root. Enamel (over the crown) and cementum (over the neck and root) surround the dentin layer. The pulp contains nerves and blood vessels.
What is snuff dipper’s pouch? An area between the cheek and the gum where leukoplakia often develops
Disorders of the mouth and teeth. A, Snuff dipper’s pouch. This individual has developed leukoplakia in the area between cheek and gum used for placement of chewing tobacco. B, Squamous cell carcinoma of lip. Excessive long-term exposure to ultraviolet light (UV) such as in sunlight increases the risk of skin cancer. C, Dental caries. These permanent defects, or cavities, are filled with decayed dental tissues. (A, From Regezi JA, Sciubba JJ, Pogrel MA: Atlas of oral and maxillofacial pathology , Philadelphia, 2000, Saunders., B, From Swartz MH: Textbook of physical diagnosis , ed 4, Philadelphia, 2002, Saunders., C, From Grundy JR, Jones JG: A color atlas of clinical operative dentistry: crowns and bridges , ed 2, London, 1993, Mosby-Wolfe.)
Dental implant. A permanent dental prosthesis will be affixed to the anchor after bone grows and healing has occurred. (From Christensen GJ: A consumer’s guide to dentistry , ed 2, St Louis, 2002, Mosby.)
Oral thrush (Candida albicans). Inflamed mucous membrane is covered with patches of creamy-white exudates. (From Emond R, Welsby P, Rowland H: Colour atlas of infectious diseases , ed 4, Edinburgh, 2003, Mosby.)
What is cleft lip? An abnormality that results in f ailure of the upper lip to close properly What is a cleft palate? An abnormality that results in failure of the palate to close or fuse properly How and when are cleft lip and palate treated? Both deformities are treated surgically. Cleft lip is repaired soon after birth, and cleft palate is repaired within the first year of life.
Congenital defects of the mouth. A, Bilateral cleft lip in an infant. B, Cleft palate. (A, From Wilson SF, Giddens JF: Health assessment for nursing practice , ed 2, St Louis, 2001, Mosby., B, From Greig JD, Garden OJ: Color atlas of surgical diagnosis , London, 1996, Times Mirror International Publishers.)
Location of the salivary glands. A, The salivary glands and their associated ducts. B, Photo shows the inflamed opening of the parotid duct into the mouth of a patient with mumps. C, Mumps (paramyxovirus) inflammation and swelling of the parotid gland in a child. (A, Rolin Graphics., B, From Emond R, Welsby P, Rowland H: Colour atlas of infectious diseases , ed 4, Edinburgh, 2003, Mosby., C, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 5, Philadelphia, 2007, Mosby. Courtesy GDW McKendrick, MD.)
What do the salivary glands secrete? Saliva What important digestive enzyme is in saliva? Salivary amylase, which begins the chemical digestion of carbohydrates Where does the process of digestion begin? In the mouth
The pharynx is a tubelike structure made of muscle and lined with mucous membrane. What two systems are served by the pharynx? It serves both the respiratory system and the digestive system. Air must pass through the pharynx on its way to the lungs. Food must pass through the pharynx on its way to the stomach.
Pharynx. This midsagittal section shows the three divisions of the pharynx (nasopharynx, oropharynx, and laryngopharynx) and nearby structures.
Layers of the small intestine. The four layers include the mucosa, submucosa, muscularis, and serosa.
Peristalsis conducts food to the stomach. Mucous membrane secretion facilitates passage of food.
Gastroesophageal reflux disease (GERD). Reflux of gastric acid up into the esophagus, causing irritation of the lining of the esophagus.
Hiatal hernia. Note herniated portion of stomach pushed through diaphragm. LES, Lower esophageal sphincter.
Discuss the location of the stomach relative to other structures of the gastrointestinal tract and other structures of the body. Discuss gastric juice composition and function. Explain how the three muscle layers running lengthwise, crosswise, and obliquely contribute to the process of digestion.
What are rugae? The lining of the stomach lies in folds called rugae when the stomach is empty.
Stomach. A portion of the anterior wall has been cut away to reveal the three muscle layers of the stomach wall. Notice that the mucosa lining the stomach forms folds called rugae.
Gastroenterology is the study of the stomach and intestines and their diseases. Disorders and diseases of the stomach usually present one or more of the following symptoms: gastritis, anorexia, nausea, or emesis. What is triple therapy? Three medications are taken concurrently for 2 to 4 weeks to treat ulcers and Crohn disease. The medications are Pepto-Bismol and two antibiotics.
Discuss the function of the villi and microvilli and how they are a prime example of the intimate relationship between structure and function. Villi project into the lumen of the intestine. Each villus contains a rich network of blood capillaries to absorb the products of carbohydrate and protein digestion and lymph capillaries (lacteals) to absorb fats. Microvilli are tiny villi on the villi that phenomenally increase the surface area for absorption.
The small intestine. A, Note the four tissue coats or layers and the presence of villi and microvilli, whichincrease the area available for absorption. B, X-ray study. C, Laparoscopic view. (B, From Weir J, Abrahams PH: Imaging atlas of human anatomy , ed 3, St Louis, 2004, Mosby., C, From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby.)
What are some of the common symptoms of malabsorption syndrome? Anorexia, abdominal bloating, cramps, anemia, and fatigue These same symptoms often occur in many other diseases of the digestive tract. How then is a definitive diagnosis often made? With information gained from endoscopy and x-ray studies
What are the two main components of bile? Cholesterol and bile pigments that emulsify fat What effect might dieting have on the production of bile? Severely obese individuals produce higher levels of cholesterol and have an increased risk of developing gallstones. Significant and rapid weight loss greatly increases the risk of symptomatic gallstone formation. What is jaundice? A yellowish skin color that develops from bile pigments being absorbed into the blood. Explain under what circumstances it might occur. Blockage of the common bile duct prevents bile from draining into the duodenum.
The gallbladder and bile ducts . Obstruction of the hepatic or common bile duct by stone or spasm blocks the exit of bile from the liver, where it is formed, and prevents bile from being ejected into the duodenum. The drawing shows gallstone locations: in the gallbladder (a), blocking the cystic duct (b), in the common bile duct (c), and blocking both the pancreatic duct and the common bile duct (d). Inset shows an x-ray of the gallbladder and the ducts that carry bile taken during a specialized procedure called an endoscopic cholangiography . See text for explanation. Inset: 1, Common bile duct; 2, common hepatic duct; 3, cystic duct; 4, gallbladder; 5, left hepatic duct; 6, liver shadow with tributaries of hepatic ducts; 7, right hepatic duct. (From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby., X-Ray: From Abrahams PH, Marks S, Hutchings R: McMinn’s color atlas of human anatomy , ed 5, Philadelphia, 2003, Mosby.)
What would happen if the common bile duct were obstructed by a gallstone? The condition of cholelithiasis occurs. What signs and symptoms would appear? Gray-white feces would be passed because of the absence of bile pigments; jaundice would occur because of bile pigments being absorbed into the blood; pain, called biliary colic, would be felt. What would happen if the cystic duct was blocked? No jaundice would occur. What extreme diets are more commonly associated with the formation of gallstones? Rapid weight loss diets What is the relationship between significant weight loss and gallstones? Significant and rapid weight loss greatly increases the risk of gallstone formation.
Gallstones. A, Inflamed gallbladder filled with yellow cholesterol gallstones. B, Laparoscopic view of the gallbladder before removal. (Courtesy Thompson JM, Wilson SF: Health assessment for nursing practice , St Louis, 1996, Mosby.)
Discuss the differences among hepatitis A, B, and C. Hepatitis is a general term referring to inflammation of the liver characterized by jaundice, liver enlargement, anorexia, abdominal discomfort, gray-white feces, and dark urine. A number of different conditions can cause hepatitis. The letters associated with the disease distinguish the cause: Hepatitis A is caused by a virus and contracted through contaminated food; Hepatitis B is also caused by a virus and is contracted through contact with contaminated blood or improperly sterilized equipment; Hepatitis C is caused by a virus and associated with transfusion of contaminated blood or intravenous drug use.
Portal hypertension is high blood pressure in the hepatic portal veins caused by obstruction of blood flow in a diseased liver. What is the danger of this condition? Varicosities of surrounding veins occur. These can rupture and cause death.
Liver damage. A, Alcoholic cirrhosis where liver surface is hard and covered with nodules that look like pebbles. B, Varicose veins (varicies) of the esophagus caused by reduction of blood flow through liver with cirrhosis. (A, Copyright Kevin Patton, Lion Den Inc, Weldon Spring, MO.)
The pancreatic duct joins the common bile duct and empties into the duodenum. Why is pancreatic juice the most important digestive juice? It contains enzymes that digest all three major kinds of food (carbohydrates, fats, proteins).
How long does it normally take for food to pass through the entire alimentary canal? 3 to 5 days Of what consistency is the chyme by the time it reaches the large intestine? The consistency of chyme changes to a more solid fecal matter as water and salts are reabsorbed from it back into the body. Is it still referred to as chyme at this point? No, it is then called feces. From what food materials can the large intestine extract some nutrient value? From cellulose and other fibrous materials What is in the large intestine that enables this digestion? Bacteria What other functions do the intestinal bacteria perform? Synthesis of vitamin K and some B-complex vitamins
Divisions of the large intestine. A, Artist’s drawing of the large intestine. B, X-ray of large intestine and terminal ileum filled with barium contrast material (barium enema). C, X-ray of a barium enema showing diverticulosis (arrowheads). D, Acute appendicitis. Appendix is gangrenous and showing signs of ischemia and putrefaction. (B, Courtesy Thompson JM, Wilson SF: Health assessment for nursing practice , St Louis, 1996, Mosby., C, From Chabner DE: The language of medicine , ed 8, St Louis, 2008, Mosby., D, From Zitelli BJ, Davis HW: Atlas of pediatric physical diagnosis , ed 3, Philadelphia, 1997, Mosby.)
Colorectal cancer is the second leading cause of death from cancer in the United States. What are some of the early warning signs? Change in bowel habits, decreased stool diameter, bleeding in stool, abdominal pain, anemia, weight loss, and fatigue Colon cancer is often treated by surgically creating a colostomy. What is this procedure? It involves diversion of a part of the colon to an opening on the abdomen.
The parietal layer lines the abdominal cavity. The visceral layer forms the outer covering of each abdominal organ. The peritoneal space is the space between the two layers. What is contained in the peritoneal space and what function does it serve? It contains peritoneal fluid, which serves to keep both layers of the peritoneum moist and able to slide freely against each other to reduce friction during breathing and peristalsis.
The peritoneum. A, The parietal layer of the peritoneum lines the abdominopelvic cavity and then extends as a series of mesenteries to form the visceral layer that covers abdominal organs. B, The transversecolon and greater omentum are raised and the small intestine is pulled to the side to show the mesentery.
Ascites. Ascites results from an accumulation of fluid in the peritoneal space. The arrows indicate water filtering out of the peritoneal blood vessels, resulting from hypertension, or diff using out of the vessels because of an osmotic imbalance in the blood. ( Photo: From Swartz MH: Textbook of physical diagnosis , ed 4, Philadelphia, 2002, Saunders.)
How do mechanical and chemical digestion differ? Mechanical digestion breaks food into tiny particles, mixes them with digestive juices, and moves them along the alimentary canal until the digestive wastes are eliminated through the anus. Chewing (mastication), swallowing (deglutition), peristalsis, and defecation are the main processes of mechanical digestion. Chemical digestion breaks down large, nonabsorbable food molecules into smaller, absorbable molecules that can pass through the intestinal mucosa into blood and lymph.
What is the difference between simple sugars and complex sugars? Complex sugars are broken down into simple sugars for use as energy. Why do complex sugars have to be broken down to be absorbed? They are too large to be absorbed. Why is active transport used to move monosaccharides into the cell, but diffusion is used to get them into the blood capillaries? Monosaccharides can diffuse through the villi into the capillaries because the process of diffusion can transport substances from a greater concentration to a lesser concentration; active transport is necessary to move monosaccharides into the cell. What are the major end products of carbohydrate digestion? Simple sugars, especially glucose Discuss the cause and treatment of lactose intolerance. The cause is absence of lactase, which is needed to digest lactose; enzymes can be given orally when lactose is ingested to assist in digestion.
Why is active transport used to move amino acids into the cell, but diffusion is used to get them into the blood capillaries?
Is bile a component of chemical digestion or mechanical digestion? Mechanical digestion because of emulsification. Why? Why aren’t fatty acids secreted into the blood capillaries instead of the lacteals? They won’t mix with water. Why is diffusion used to move amino acids into the cell, but secretion is used to get them into the lymph capillaries (lacteals)?
What is the difference between digestion and absorption of foods? Digestion simply breaks food down; absorption transports the nutrients of food into the blood stream so they be used by body cells. What is the significance of salt being actively transported through the intestinal mucosa? It responds to the sodium needs of the body. What is the principle on which fluid replacement drinks such as Gatorade and other sport drinks are based? An electrolyte solution is absorbed to avoid water intoxication.
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