Gastroenterology The medical specialty that studies the anatomy and physiology of the gastrointestinal system and uses diagnostic tests, medical and surgical procedures, and drugs to treat gastrointestinal diseases.

Anatomy and Physiology Gastrointestinal System – Begins at the mouth, continues through the thoracic cavity, and fills most of the abdominal cavity – Upper gastrointestinal system includes the structures from the mouth through the stomach

Anatomy and Physiology (con’t) Gastrointestinal System (con’t) – Lower gastrointestinal system includes the small and large intestines – Purpose is to digest food, absorb nutrients, and remove undigested material (waste) from the body

Figure 3-1 Gastrointestinal system

Anatomy of the Gastrointestinal System Oral Cavity and Pharynx – Begins in the mouth, or oral cavity – Oral cavity contains the teeth; tongue; hard palate; and soft palate with its fleshy, hanging uvula. – Saliva also contains an enzyme that begins the process of digestion.

Anatomy of the Gastrointestinal System (con't) Oral Cavity and Pharynx (con’t) – There are three pairs of salivary glands: the parotid glands, the sublingual glands, and the submandibular glands. – The teeth tear, chew, and grind the food during the process of mastication. – The tongue moves food toward the teeth and mixes food with saliva.

Anatomy of the Gastrointestinal System (con't) Oral Cavity and Pharynx (con’t) – Swallowing or deglutition moves food into the throat or pharynx. – When food is swallowed, the epiglottis closes the entrance to the larynx, so that food in the back of the throat, pressing on the uvula, does not initiate the gag reflex.

Figure 3-2 Oral cavity and pharynx

Figure 3-3 Salivary glands

Anatomy of the Gastrointestinal System (con't) Esophagus – A flexible, muscular tube that connects the pharynx to the stomach.

Anatomy of the Gastrointestinal System (con't) Stomach – Divided into four areas: the cardia, fundus, body, and pylorus. – The gastric mucosa is arranged in thick, deep folds known as rugae which expand as the stomach fills with food.

Anatomy of the Gastrointestinal System (con't) Stomach (con’t) – Two sphincters (muscular rings) keep food in the stomach. – The lower esophageal sphincter is located in the distal esophagus.

Figure 3-4 Stomach

Anatomy of the Gastrointestinal System (con't) Small Intestine – The small intestine is a long, hollow tube that receives chyme from the stomach. – It is divided into three parts: the duodenum, jejunum, and ileum.

Figure 3-5 Small and large intestines

Anatomy of the Gastrointestinal System (con't) Large Intestine – A larger, hollow tube that receives undigested material and water from the small intestine. – Consists of the cecum, colon, rectum, and anus.

Anatomy of the Gastrointestinal System (con't) Large Intestine (con’t) – Waves of peristalsis slowly move undigested material through the large intestine as water is absorbed through the intestinal wall and into the blood. – The colon is the longest part. – It travels through all four quadrants of the abdomen as the ascending colon, transverse colon, descending colon, and sigmoid colon.

Anatomy of the Gastrointestinal System (con't) Abdomen and Abdominopelvic Cavity – Contains the largest organs of the gastrointestinal system. – The walls of the abdominopelvic cavity are lined by peritoneum, a membrane that secretes peritoneal fluid. – This watery fluid fills the spaces between the organs and allows them to slide past each other during the movements of digestion.

Anatomy of the Gastrointestinal System (con't) The blood supply to the stomach, small intestine, liver, gallbladder, and pancreas comes from the celiac trunk of the aorta, the largest artery in the body.

Anatomy of the Gastrointestinal System (con't) Liver – The liver is the largest solid organ in the body, located in the upper right abdominal cavity. – An accessory organ of digestion that contributes to, but is not physically involved in, the process of digestion.

Figure 3-6 Biliary tree

Anatomy of the Gastrointestinal System (con't) Gallbladder – An accessory organ of digestion posterior to the liver. – Concentrates and stores bile from the liver.

Anatomy of the Gastrointestinal System (con't) Pancreas – An accessory organ of digestion posterior to the stomach. – Presence of food in the duodenum causes the pancreas to secrete digestive enzymes into the pancreatic duct to the duodenum. – Also functions as an organ of the endocrine system.

Physiology of Digestion There are two parts to digestion: – Mechanical – Chemical Mechanical digestion uses mastication, deglutition, and peristalsis to break down foods. Mechanical digestion also involves breaking apart fats in the duodenum.

Physiology of Digestion (con't) The enzyme amylase in saliva begins to break down carbohydrate foods in the mouth. The stomach secretes the following substances that continue the process of chemical digestion: – Hydrochloric acid – Pepsinogen – Gastrin

Chemical digestion is completed in the small intestine. Cholecystokinin stimulates the pancreas to secrete four digestive enzymes into the duodenum: – Amylase – Lipase – Protease – Other enzymes that break down proteins Physiology of Digestion (con't)

The liver plays an important role in regulating nutrients such as glucose and amino acids. Excess glucose in the blood is stored in the liver as glycogen and released when the blood glucose level is low. The liver uses amino acids to build plasma proteins and clotting factors for the blood. Physiology of Digestion (con't)

Figure 3-7 Gastrointestinal system. (Robert W. Ginn/PhotoEdit Inc.) Alimentary Canal Accessory Structures

Diseases and Conditions Eating – Anorexia – Dysphagia – Polyphagia

Diseases and Conditions (con't) Mouth and Lips – Cheilitis – Sialolithiasis – Stomatitis – Glossitis

Figure 3-8 Glossitis (Centers for Disease Control and Prevention [CDC])

Diseases and Conditions (con't) Esophagus and Stomach – Dyspepsia – Esophageal varices – Gastritis – Gastroenteritis – Gastroesophageal reflux disease (GERD)

Figure 3-9 Esophageal varix (David M. Martin, M.D./Photo Researchers, Inc.)

Diseases and Conditions (con't) Esophagus and Stomach (con't) – Heartburn – Hematemesis – Nausea and vomiting (N&V) – Peptic ulcer disease (PUD) – Stomach cancer

Figure 3-10 Gastric ulcer (David M. Martin, M.D./Photo Researchers, Inc.)

Diseases and Conditions (con't) Duodenum, Jejunum, Ileum – Ileus – Intussusception – Volvulus

Figure 3-11 Intussusception of the intestine

Diseases and Conditions (con't) Cecum and Colon – Appendicitis – Colic – Colon cancer – Diverticulum – Dysentery

Figure 3-12 Diverticula (David M. Martin, M.D./Photo Researchers, Inc.)

Figure 3-13 Diverticulitis and polyposis

Diseases and Conditions (con't) Cecum and Colon (con’t) – Gluten enteropathy – Inflammatory bowel disease (IBD) – Irritable bowel syndrome (IBS) – Polyp

Figure 3-14 Crohn’s disease

Figure 3-15 Colonic polyps (Staats/Custom Medical Stock Photo, Inc.)

Diseases and Conditions (con't) Rectum and Anus – Hemorrhoids – Proctitis – Rectocele

Diseases and Conditions (con't) Defecation and Feces – Constipation – Diarrhea – Flatulence – Hematochezia – Incontinence – Steatorrhea

Diseases and Conditions (con't) Abdominal Wall and Abdominal Cavity – Adhesions – Hernia – Peritonitis

Figure 3-16 Hernia (From Rudolph, A.M., Hoffman, J.I.E., & Rudolph, C.D. (Eds.) Rudolph’s Pediatrics. (19 th ed., p. 1040))

Figure 3-17 Peritonitis (Custom Medical Stock Photo, Inc.)

Diseases and Conditions (con't) Liver – Ascites – Cirrhosis – Hepatitis

Figure 3-18 Fatty liver disease and cirrhosis of the liver (Arthur Glauberman/Photo Researchers, Inc.)

Diseases and Conditions (con't) Hepatitis is the most common chronic liver disease. – Hepatitis A – Hepatitis B – Hepatitis C – Hepatitis D – Hepatitis E

Diseases and Conditions (con't) Hepatitis A is an acute but short-lived infection caused by exposure to water or food that is contaminated with feces from a person who is infected with the hepatitis A virus (HAV).

Hepatitis B is an acute infection caused by exposure to the blood of a person who is already infected with the hepatitis B virus (HBV); it is also known as serum hepatitis. It is also spread during sexual activity by contact with saliva and vaginal secretions. An infected mother can pass hepatitis B to her fetus before birth or when breastfeeding. Diseases and Conditions (con't)

Figure 3-19 Blood transfusion (PhotoDisc/Getty Images)

Hepatitis C is an acute infection caused by exposure to the blood of a person who is already infected with the hepatitis C virus (HCV). Hepatitis C is not readily transmitted by sexual activity or from a mother to her fetus. Diseases and Conditions (con't)

Chronic hepatitis C is the main cause of chronic liver disease, cirrhosis, and liver cancer. Hepatitis D is a secondary infection caused by a mutated (changed) hepatitis virus. Diseases and Conditions (con't)

Hepatitis D only develops in patients who already have hepatitis B; it is also known as delta hepatitis. Hepatitis E is similar to hepatitis A but rarely occurs in the United States. Diseases and Conditions (con't)

Hepatomegaly Jaundice Liver Cancer Diseases and Conditions (con't)

Figure 3-20 Jaundice (Dr. M.A. Ansary/Photo Researchers, Inc.)

Figure 3-21 Liver cancer (Gca/Photo Researchers, Inc.)

Diseases and Conditions (con't) Gallbladder and Bile Ducts – Cholangitis – Cholecystitis – Cholelithiasis

Figure 3-22 Cholelithiasis (Custom Medical Stock Photo, Inc.)

Figure 3-23 Gallstones in the biliary and pancreatic ducts

Diseases and Conditions (con't) Pancreas – Pancreatic cancer – Pancreatitis

Laboratory and Diagnostic Procedures Blood Tests – Albumin – Alkaline phosphatase (ALP) – ALT and AST – Bilirubin

Laboratory and Diagnostic Procedures (con't) Blood Tests (con’t) – GGT – Liver function tests (LFTs)

Laboratory and Diagnostic Procedures (con't) Gastric and Feces Specimen Tests – CLO test – Culture and sensitivity (C&S) – Fecal occult blood test – Gastric analysis – Ova and parasites (O&P)

Radiologic Procedures – Barium enema – Cholangiography Laboratory and Diagnostic Procedures (con't)

Figure 3-24 Barium enema (Custom Medical Stock Photo, Inc.)

Figure 3-25 Endoscopic retrograde cholangiopancreatography

Radiologic Procedures (con’t) – Computerized axial tomography (CAT, CT scan) – Flat plate of the abdomen – Gallbladder ultrasound Laboratory and Diagnostic Procedures (con't)

Radiologic Procedures (con’t) – Magnetic resonance imaging (MRI) scan – Oral cholecystography (OCG) Laboratory and Diagnostic Procedures (con't)

Radiologic Procedures (con’t) – Upper gastrointestinal series (UGI) Laboratory and Diagnostic Procedures (con't)

Medical and Surgical Procedures Medical Procedures – Insertion of nasogastric tube

Figure 3-26 Nasogastric tube (Pearson Education/PH College)

Medical and Surgical Procedures (con't) Surgical Procedures – Abdominocentesis – Appendectomy – Biopsy – Bowel resection and anastomosis – Cholecystectomy – Choledocholithotomy

Figure 3-27 Laparoscopic cholecystectomy (Geoff Tompkinson/Photo Researchers, Inc.)

Medical and Surgical Procedures (con't) Surgical Procedures (con’t) – Colostomy – Endoscopy – Exploratory laparotomy

Figure 3-28 Colostomy and stoma (Pearson Education/PH College)

Medical and Surgical Procedures (con't) Endoscopic Procedures – Esophagoscopy – Gastroscopy – Esophagogastroduodenoscopy (EGD) – Sigmoidoscopy – Colonoscopy

Figure 3-29 Colonoscopy (BSIP/Phototake NYC)

Medical and Surgical Procedures (con't) Surgical Procedures (con’t) – Gastrectomy – Gastroplasty – Gastrostomy – Hemorrhoidectomy

Figure 3-30 PEG tube

Medical and Surgical Procedures (con't) Surgical Procedures (con’t) – Herniorrhaphy – Jejunostomy – Liver transplantation – Polypectomy

Drug Categories These categories of drugs are used to treat gastrointestinal diseases and conditions: – Antacid drugs – Antibiotic drugs – Antidiarrheal drugs – Antiemetic drugs

Drug Categories (con’t) These categories of drugs are used to treat gastrointestinal diseases and conditions: – H2 blocker drugs – Laxative drugs – Proton pump inhibitor drugs

Abbreviations