Nursing Functions of the Large Intes-tine

CHAPTER 7 ♦ List at least three functions of the large intes- ♦ Describe at least five diseases of the digestive tine system ♦ List at least four functions of the liver ♦ Explain how the pancreas helps digest foods ♦ Define, pronounce, and spell all key terms KEY TERMS alimentary canal (ahl-ihmen⬘-tar⬙-ee) anus colon (coh⬘-lun) digestive system duodenum (dew-oh-deh⬘num) esophagus (ee⬙-sof⬘-eh-gus) gallbladder hard palate ileum (ill⬘-ee⬙-um) jejunum (jeh-jew⬘-num) large intestine liver mouth pancreas (pan⬘-cree⬙-as) peristalsis (pair⬙-ih-stall⬙-sis) pharynx (far⬘-inks) rectum salivary glands small intestine soft palate stomach teeth tongue vermiform appendix villi (vil⬘-lie) RELATED HEALTH CAREERS ◆ Dental Assistant ◆ Dietitian ◆ Hepatologist ◆ Dental Hygienist ◆ Enterostomal RN or ◆ Internist ◆ Dentist ◆ Dietetic Assistant Technician ◆ Proctologist ◆ Gastroenterologist 7:11 INFORMATION The digestive system, also known as the gastrointestinal system, is responsible for the physical and chemical breakdown of food so that it can be taken into the bloodstream and used by body cells and tissues. The system consists of the alimentary canal and accessory organs (figure 7-56). The alimentary canal is a long, muscular tube that begins at the mouth and includes the mouth (oral cavity), pharynx, esophagus, stomach, small intestine, large intestine, and anus. The accessory organs are the salivary glands, tongue, teeth, liver, gallbladder, and pancreas. PARTS OF THE ALIMENTARY CANAL The mouth, also called the buccal cavity (figure 7-57) receives food as it enters the body. While food is in the mouth, it is tasted, broken down physically by the teeth, lubricated and partially digested by saliva, and swallowed. The teeth are special structures in the mouth that physically break down food by chewing and grinding. This process is called mastication. The tongue is a muscular organ that contains special receptors called taste buds. The taste buds allow a person to taste sweet, salty, sour, and bitter sensations. The Anatomy and Physiology Oral cavity Parotid gland Lips Teeth Pharynx Tongue Submandibular gland Sublingual gland Esophagus Diaphragm Liver Stomach Hepatic duct Cystic duct Pylorus of the stomach Gallbladder Pancreas Transverse colon of large intestine Duodenum Ascending colon of large intestine Jejunum of small intestine Ileum of small intestine Descending colon of large intestine Sigmoid colon of large intestine Cecum Vermiform appendix Rectum Anus FIGURE 7-56 The digestive system. tongue also aids in chewing and swallowing food. The hard palate is the bony structure that forms the roof of the mouth and separates the mouth from the nasal cavities. Behind the hard palate is the soft palate, which separates the mouth from the nasopharynx. The uvula, a cone-shaped muscular structure, hangs from the middle of the soft palate. It prevents food from entering the nasopharynx during swallowing. Three pairs of salivary glands, the parotid, sublingual, and submandibular, produce a liquid called saliva. Saliva lubricates the mouth during speech and chewing and moistens food so that it can be swallowed easily. Saliva also contains an enzyme (a substance that speeds up a chemical reaction) called salivary amylase, formerly known as ptyalin. Salivary amylase begins the chemical break- down of carbohydrates, or starches, into sugars that can be taken into the body. After the food is chewed and mixed with saliva, it is called a bolus. When the bolus is swallowed, it enters the pharynx (throat). The pharynx is a tube that carries both air and food. It carries the air to the trachea, or windpipe, and food to the esophagus. When a bolus is being swallowed, muscle action causes the epiglottis to close over the larynx, preventing the bolus from entering the respiratory tract and causing it to enter the esophagus. The esophagus is the muscular tube dorsal to (behind) the trachea. This tube receives the bolus from the pharynx and carries the bolus to the stomach. The esophagus, like the remaining part of the alimentary canal, relies on a rhythmic, CHAPTER 7 Gum (gingiva) Upper lip Labial frenulum Hard palate Palatine tonsil Soft palate Uvula Lingual frenulum Tongue Teeth Gum (gingiva) Lower lip Labial frenulum FIGURE 7-57 Parts of the oral cavity, or mouth. wavelike, involuntary movement of its muscles called peristalsis to move the food in a forward direction. The stomach is an enlarged part of the alimentary canal. It receives the food from the esophagus. The mucous membrane lining of the stomach contains folds, called rugae. These disappear as the stomach fills with food and expands. The cardiac sphincter, a circular muscle between the esophagus and stomach, closes after food enters the stomach and prevents food from going back up into the esophagus. The pyloric sphincter, a circular muscle between the stomach and small intestine, keeps food in the stomach until the food is ready to enter the small intestine. Food usually remains in the stomach for approximately 2–4 hours. During this time, food is converted into a semifluid material, called chyme, by gastric juices produced by glands in the stomach. The gastric juices contain hydrochloric acid and enzymes. Hydrochloric acid kills bacteria, facilitates iron absorption, and activates the enzyme pepsin. The enzymes in gastric juices include lipase, which starts the chemical breakdown of fats, and pepsin, which starts protein digestion. In infants, the enzyme rennin is also secreted to aid in the digestion of milk. Rennin is not present in adults. When the food, in the form of chyme, leaves the stomach, it enters the small intestine. The small intestine is a coiled section of the ali- mentary canal. It is approximately 20 feet in length and 1 inch in diameter, and is divided into three sections: the duodenum, the jejunum, and the ileum. The duodenum is the first 9–10 inches of the small intestine. Bile (from the gallbladder and liver) and pancreatic juice (from the pancreas) enter this section through ducts, or tubes. The jejunum is approximately 8 feet in length and forms the middle section of the small intestine. The ileum is the final 12 feet of the small intestine, and it connects with the large intestine at the cecum. The circular muscle called the ileocecal valve separates the ileum and cecum and prevents food from returning to the ileum. While food is in the small intestine, the process of digestion is completed, and the products of digestion are absorbed into the bloodstream for use by the body cells. Intestinal juices, produced by the small intestine, contain the enzymes maltase, sucrase, and lactase, which break down sugars into simpler forms. The intestinal juices also contain enzymes known as peptidases, which complete the digestion of proteins, and steapsin (lipase), which aids in the digestion of fat. Bile from the liver and gallbladder emulsifies (physically breaks down) fats. Enzymes from the pancreatic juice complete the process of digestion. These enzymes include pancreatic amylase or amylopsin (which acts on sugars), trypsin and chymotrypsin (which act on proteins), and lipase or steapsin (which acts on fats). After food has been digested, it is absorbed into the bloodstream. The walls of the small intestine are lined with fingerlike projections called villi (figure 7-58). The villi contain blood capillaries and lacteals. The blood capillaries absorb the digested nutrients and carry them to the liver, where they are either stored or released into general circulation for use by the body cells. The lacteals absorb most of the digested fats and carry them to the thoracic duct in the lymphatic system, which releases them into the circulatory system. When food has completed its passage through the small intestine, only wastes, indigestible materials, and excess water remain. The large intestine is the final section of the alimentary canal. It is approximately 5 feet in length and 2 inches in diameter. Functions include absorption of water and any remaining nutrients; storage of indigestible materials before they are eliminated from the body; synthesis (formation) and absorption of some B-complex vitamins and vitamin K by bacteria present in the Anatomy and Physiology Capillary network in villus Lacteal Epithelial cells Intestinal gland Artery Vein Lymph vessel Circular muscles Longitudinal muscles Peritoneum FIGURE 7-58 Lymphatic and blood capillaries in the villi of the small intestine provide for the absorption of the products of digestion. intestine; and transportation of waste products out of the alimentary canal. The large intestine is divided into a series of connected sections. The cecum is the first section and is connected to the ileum of the small intestine. It contains a small projection, called the vermiform appendix. The next section, the colon, has several divisions. The ascending colon continues up on the right side of the body from the cecum to the lower part of the liver. The transverse colon extends across the abdomen, below the liver and stomach and above the small intestine. The descending colon extends down the left side of the body. It connects with the sigmoid colon, an S-shaped section that joins with the rectum. The rectum is the final 6–8 inches of the large intestine and is a storage area for indigestibles and wastes. It has a narrow canal, called the anal canal, which opens at a hole, called the anus. Fecal material, or stool, the final waste product of the digestive process, is expelled through this opening. Left lobe of liver Right hepatic duct Cystic duct Left hepatic duct Common hepatic duct Gallbladder Tail of pancreas Common bile duct Head of pancreas Sphincter of Oddi Main pancreatic duct Duodenum FIGURE 7-59 The liver, gallbladder, and pancreas. ACCESSORY ORGANS The liver (figure 7-59), is the largest gland in the body and is an accessory organ to the digestive system. It is located under the diaphragm and in the upper right quadrant of the abdomen. The liver secretes bile, which is used to emulsify fats in the digestive tract. Bile also makes fats water soluble, which is necessary for absorption. The liver stores sugar in the form of glycogen. The glycogen is converted to glucose and released into the bloodstream when additional blood sugar is needed. The liver also stores iron and certain vitamins. It produces heparin, which prevents clotting of the blood; blood proteins such as fibrinogen and prothrombin, which aid in clot- CHAPTER 7 ting of the blood; and cholesterol. Finally, the liver detoxifies (renders less harmful) substances such as alcohol and pesticides, and destroys bacteria that have been taken into the blood from the intestine. The gallbladder is a small, muscular sac located under the liver and attached to it by connective tissue. It stores and concentrates bile, which it receives from the liver. When the bile is needed to emulsify fats in the digestive tract, the gallbladder contracts and pushes the bile through the cystic duct into the common bile duct, which drains into the duodenum. The pancreas is a glandular organ located behind the stomach. It produces pancreatic juices, which contain enzymes to digest food. These juices enter the duodenum through the pancreatic duct. The enzymes in the juices include pancreatic amylase or amylopsin (to break down sugars), trypsin and chymotrypsin (to break down proteins), and lipase or steapsin (to act on fats). The pancreas also produces insulin, which is secreted into the bloodstream. Insulin regulates the metabolism, or burning, of carbohydrates to convert glucose (blood sugar) to energy. DISEASES AND ABNORMAL CONDITIONS pain that starts under the rib cage and radiates to the right shoulder. If a gallstone blocks the bile ducts, the gallbladder can rupture and cause peritonitis. Treatment methods include a low-fat diet, lithotripsy (shock waves that are used to shatter the gallstones), and/or a cholecystectomy (surgical removal of the gallbladder). Cirrhosis Cirrhosis is a chronic destruction of liver cells accompanied by the formation of fibrous connective and scar tissue. Causes include hepatitis, bile duct disease, chemical toxins, and malnutrition associated with alcoholism. Symptoms vary and become more severe as the disease progresses. Some common symptoms are liver enlargement, anemia, indigestion, nausea, edema in the legs and feet, hematemesis (vomiting blood), nosebleeds, jaundice (yellow discoloration), and ascites (an accumulation of fluid in the abdominal peritoneal cavity). When the liver fails, disorientation, hallucinations, hepatic coma, and death occur. Treatment is directed toward preventing further damage to the liver. Alcohol avoidance, proper nutrition, vitamin supplements, diuretics (to reduce ascites and edema), rest, infection prevention, and appropriate exercise are encouraged. A liver transplant may be performed if too much of the liver is destroyed. Appendicitis Constipation Appendicitis is an acute inflammation of the appendix, usually resulting from an obstruction and infection. Symptoms include generalized abdominal pain that later localizes at the lower right quadrant, nausea and vomiting, mild fever, and elevated white blood cell count. If the appendix ruptures, the infectious material will spill into the peritoneal cavity and cause peritonitis, a serious condition. Appendicitis is treated by an appendectomy (surgical removal of the appendix). Constipation is when fecal material remains in the colon too long, causing excessive reabsorption of water. The feces or stool becomes hard, dry, and difficult to eliminate. Causes include poor bowel habits, chronic laxative use leading to a “lazy” bowel, a diet low in fiber, and certain digestive diseases. The condition is usually corrected by a highfiber diet, adequate fluids, and exercise. Although laxatives are sometimes used to stimulate defecation, frequent laxative use may be habit forming and lead to chronic constipation. Cholecystitis Cholecystitis is an inflammation of the gallbladder. When gallstones form from crystallized cholesterol, bile salts, and bile pigments, the condition is known as cholelithiasis. Symptoms frequently occur after eating fatty foods and include indigestion, nausea and vomiting, and Diarrhea Diarrhea is a condition characterized by frequent watery stools. Causes include infection, stress, diet, an irritated colon, and toxic substances. Diarrhea can be extremely dangerous in infants and small children because of the excessive fluid Anatomy and Physiology loss. Treatment is directed toward eliminating the cause, providing adequate fl uid intake, and modifying the diet. Diverticulitis Diverticulitis is an inflammation of the diverticula, pouches (or sacs) that form in the intestine as the mucosal lining pushes through the surrounding muscle. When fecal material and bacteria become trapped in the diverticula, inflammation occurs. This can result in an abscess or rupture, leading to peritonitis. Symptoms vary depending on the amount of inflammation but may include abdominal pain, irregular bowel movements, flatus (gas), constipation or diarrhea, abdominal distention (swelling), low-grade fever, and nausea and vomiting. Treatment methods include antibiotics, stoolsoftening medications, pain medications, highfiber diet, and in severe cases, surgery to remove the affected section of colon. Gastroenteritis Gastroenteritis is an inflammation of the mucous membrane that lines the stomach and intestinal tract. Causes include food poisoning, infection, and toxins. Symptoms include abdominal cramping, nausea, vomiting, fever, and diarrhea. Usual treatment methods are rest and increased fluid intake. In severe cases, antibiotics, intravenous fluids, and medications to slow peristalsis may be used. Hemorrhoids Hemorrhoids are painful dilated or varicose veins of the rectum and/or anus. They may be caused by straining to defecate, constipation, pressure during pregnancy, insufficient fluid intake, laxative abuse, and prolonged sitting or standing. Symptoms include pain, itching, and bleeding. Treatment methods include a high-fiber diet; increased fluid intake; stool softeners; sitz baths or warm, moist compresses; and in some cases, a hemorrhoidectomy (surgical removal of the hemorrhoids). Hepatitis Hepatitis is a viral inflammation of the liver. Type A, HAV or infectious hepatitis, is highly contagious and is transmitted in food or water con- taminated by the feces of an infected person. It is the most benign form of hepatitis and is usually self-limiting. A vaccine is available to prevent hepatitis A. Type B, HBV, or serum hepatitis, is transmitted by body fl uids including blood, serum, saliva, urine, semen, vaginal secretions, and breast milk. It is more serious than type A and can lead to chronic hepatitis or to cirrhosis of the liver. A vaccine developed to prevent hepatitis B is recommended for all health care workers. Type C, or HCV, is also spread through contact with blood or body fluids. The main methods of transmission include sharing needles while injecting drugs, getting stuck with a contaminated needle or sharps while on the job, or passing the virus from an infected mother to the infant during birth. Hepatitis C is much more likely to progress to chronic hepatitis, cirrhosis, or both. There is no vaccine for type C. Other strains of the hepatitis virus that have been identified include types D and E. Symptoms include fever, anorexia (lack of appetite), nausea, vomiting, fatigue, darkcolored urine, clay-colored stool, myalgia (muscle pain), enlarged liver, and jaundice. Treatment methods include rest and a diet high in protein and calories and low in fat. A liver transplant may be necessary if the liver is severely damaged. Hernia A hernia, or rupture, occurs when an internal organ pushes through a weakened area or natural opening in a body wall. A hiatal hernia is when the stomach protrudes through the diaphragm and into the chest cavity through the opening for the esophagus (figure 7-60). Symptoms include heartburn, stomach distention, chest pain, and difficult swallowing. Treatment methods include a bland diet, small frequent meals, staying upright after eating, and surgical repair. An inguinal hernia is when a section of the small intestine protrudes through the inguinal rings of the lower abdominal wall. If the hernia cannot be reduced (pushed back in place), a herniorrhaphy (surgical repair) is performed. Pancreatitis Pancreatitis is an inflammation of the pancreas. The pancreatic enzymes begin to digest the pancreas itself, and the pancreas becomes necrotic, inflamed, and edematous. If the damage extends CHAPTER 7 Esophagus This part of the stomach is normally located below the diaphragm. Cardiac sphincter Diaphragm Stomach Pyloric sphincter FIGURE 7-60 A hiatal hernia occurs when the stomach protrudes through the diaphragm. to blood vessels in the pancreas, hemorrhage and shock occur. Pancreatitis may be caused by excessive alcohol consumption or blockage of pancreatic ducts by gallstones. Many cases are idiopathic, or of unknown cause. Symptoms include severe abdominal pain that radiates to the back, nausea, vomiting, diaphoresis (excessive perspiration), and jaundice if swelling blocks the common bile duct. Treatment depends on the cause. A cholecystectomy, removal of the gall bladder, is performed if gallstones are the cause. Analgesics for pain and nutritional support are used if the cause of pancreatitis is alcoholism or idiopathic. This type of pancreatitis has a poor prognosis and often results in death. Peritonitis Peritonitis, an inflammation of the abdominal peritoneal cavity, usually occurs when a rupture in the intestine allows the intestine contents to enter the peritoneal cavity. A ruptured appendix or gallbladder can cause this condition. Symptoms include abdominal pain and distention, fever, nausea, and vomiting. Treatment methods include antibiotics and, if necessary, surgical repair of the damaged intestine. Ulcer An ulcer is an open sore on the lining of the digestive tract. Peptic ulcers include gastric (stomach) ulcers and duodenal ulcers. The major cause is a bacterium, Helicobacter pylori (H. pylori), that burrows into the stomach membranes, allowing stomach acids and digestive juices to create an ulcer. Symptoms include burning pain, indigestion, hematemesis (bloody vomitus), and melena (dark, tarry stool). Usual treatment methods are antacids, a bland diet, decreased stress, and avoidance of irritants such as alcohol, fried foods, tobacco, and caffeine. If the H. pylori bacteria are present, treatment with antibiotics and a bismuth preparation, such as Pepto-Bismol, usually cures the condition. In severe cases, surgery is performed to remove the affected area. Ulcerative Colitis Ulcerative colitis is a severe inflammation of the colon accompanied by the formation of ulcers and abscesses. It is thought to be caused by stress, food allergy, or an autoimmune reaction. The main symptom is diarrhea containing blood, pus, and mucus. Other symptoms include weight loss, weakness, abdominal pain, anemia, and anorexia. Periods of remission and exacerbation are common. Treatment is directed toward controlling inflammation, reducing stress with mild sedation, maintaining proper nutrition, and avoiding substances that aggravate the condition. In some cases, surgical removal of the affected colon and creation of a colostomy (an artificial opening in the colon that allows fecal material to be excreted through the abdominal wall) is necessary. STUDENT: Go to the workbook and complete the assignment sheet for 7:11, Digestive System. 7:12 Urinary System Objectives After completing this section, you should be able to: ♦ Label a diagram of the urinary system ♦ Explain the action of the following parts of a nephron: glomerulus, Bowman’s capsule, convoluted tubule, and collecting tubule