The Digestive System

1. Chapter 18 The Digestive System

2. The Digestive System • The group of organs that changes food that has been eaten into a form that can be used by the body’s cells • Also known as the gastrointestinal (GI) tract or system • The connecting chain of organs is sometimes referred to as the alimentary canal.

3. The Digestive System

4. Four Phases of the Digestive System • Ingestion: taking in food or water • Digestion: breaks food down into nutrients • Absorption: enzymes used in the intestines • Elimination: urination or defecation of waste

5. Defining Digestion • Digestion is the activity performed by the organs of the digestive system. • Digestion is defined as the process by which food is broken down, mechanically and chemically, in the GI tract into converted into an absorbable form that can be used by the cells of the body.

6. Raw Materials Required for a Healthy Body • Carbohydrates provide energy. • Proteins build and repair cells and tissue. • Fats are a secondary energy source. • Vitamins are regulating chemicals needed for growth and control of body activities. • Minerals are needed by the body for the muscles, nerves, blood, teeth, and bones.

7. Raw Materials Required for a Healthy Body • Water regulates temperature, adds moisture to waste, and lubricates. • Roughage speeds up the digestive process.

8. The Process of Swallowing • The bolus can go in three directions: • Up the nose • Down and forward into the trachea • Down into the esophagus • The bolus raises the soft palate as it is swallowed and closes off the nasal cavity.

9. The Process of Swallowing • The epiglottis moves across the opening to the larynx as the tongue pushes the bolus against the palate. • At the moment of swallowing, the larynx moves upward against the epiglottis to close the opening off to the larynx. • The bolus enters the esophagus.

10. How the Esophagus Works • Involuntary muscle action, called peristalsis, moves the bolus down the esophagus by alternately contracting and relaxing against the bolus. • The bolus then moves down into the stomach.

11. The Stomach

12. The Structure and Function of the Stomach • The upper opening to the stomach is called the cardiac sphincter. • This sphincter opens to allow the bolus to enter, and closes to prevent the bolus from going back up into the esophagus.

13. The Structure and Function of the Stomach • The stomach is an organ made up of three layers of strong muscle tissue. • The stomach has folds, called rugae, that allow it to expand as the bolus enters. • The stomach begins to contract when the bolus enters and the bolus is mixed with gastric enzymes and hydrochloric acid as the chemical process of breaking down food continues.

14. The Structure and Function of the Stomach • The bolus of partially digested food is changed into a semiliquid solution called chyme. • When the consistency of the chyme is right, the pyloric sphincter muscle at the end of the stomach opens and allows the chyme to enter the small intestine.

15. The Structure and Function of the Small Intestine • The small intestine absorbs the nutrients from the chyme. • About 1 inch in diameter and about 20 feet in length • Three sections: • Duodenum • Jejunum • Ileum

16. The Functions of the Liver • The largest gland in the body • Secretes bile, which is required to digest fats • Stores glycogen to be used when the body needs additional blood sugar

17. The Functions of the Liver • Processes proteins that burn fats as fuel or store fats • Manufactures substances required for the process of clotting blood • Produces antibodies to counteract certain disease organisms

18. The Role of the Gallbladder • The gallbladder is a small sac attached to the underside of the liver. • The sole purpose of the gallbladder is to concentrate and store bile to aid in the digestion of fats.

19. The Location and Function of the Pancreas • The pancreas lies beneath the stomach with its head in the curve of the duodenum. • The pancreas has two functions as a gland: • Exocrine gland: secretes pancreatic juices directly into the duodenum • Endocrine gland: secretes insulin directly into the bloodstream

20. How and Where Nutrients Are Absorbed • Absorption occurs in the millions of villi that line the major part of the small intestine. • The swinging motion of the villi keeps the chyme mixed with digestive juices. • The external cells of the villi absorb nutrients, minerals, and water from the chyme.

21. How and Where Nutrients Are Absorbed • With useful nutrients and other substances absorbed from the chyme, waste enters the large intestine.

22. The Large Intestine

23. The Sections of the Colon • The large intestine is also called the colon. • The ascending colon continues upward along the right side of the abdomen. • The transverse colon extends in a loop across the abdominal cavity. • The descending colon extends down the left side of the abdomen until it reaches the edge of the pelvic cavity.

24. The Function of the Colon • The large intestine absorbs excess liquid from the chyme. • This water, plus some salts and proteins, are filtered out of the blood to be eliminated in urine. • This waste forms feces to be eliminated through the rectum.

25. The Structure and Function of the Rectum • Rectum is 6 to 8 inches long • The rectum serves as a collecting area for feces, the remains of digestion. • When enough material is accumulated, sensors are activated, and the urge to defecate is felt.

26. The Structure and Function of the Anal Canal and Anus • Anal canal • The anal canal is a narrow passageway that extends from rectum to anus. • This passageway is a voluntarily controlled muscle that is used to empty the rectum. • Anus • The anus is the opening of the anal canal to the outside of the body.

27. Colonoscopy • An exam that uses a fiber optic scope to view the entire large intestine • This exam requires patient preparation to clear the intestine of feces. • This is indicated in patients with complaints of diarrhea, constipation, bleeding, or pain.

28. Gastrointestinal Series (X-Rays) • Barium swallow • Uses a fluoroscope to view the action of the esophagus as the patient swallows a radiopaque liquid called barium • Upper GI series • After the barium swallow, additional barium is swallowed and the passage of the barium throughout the small intestine is observed.

29. Gastrointestinal Series (X-Rays) • Lower GI series • The barium mixture is administered as an enema and outlines the structure of the large intestine.

30. Gastroscopy • A fiber optic scope is used to view the esophagus, stomach, and upper duodenum. • This procedure can also be used to remove small foreign objects that may be blocking the air passage.

31. Nuclear Medicine Study • Scanning of structures, such as the liver or spleen, is made possible by radioactive materials. • A special camera or scanning device may be used to screen the liver for disease processes, infarcts, cysts, tumors, and organ size.

32. Occult Blood Test • When bleeding from the intestinal tract is not visible because of the small quantity, it can be detected through analysis of the feces. • Frequently used to identify bleeding associated with colorectal malignancy

33. Proctoscopy • An examination of the lower rectum and anal canal through a 3-inch-long proctoscope • Exam is preceded by a digital examination to determine sphincter condition • Proctoscope permits detection of hemorrhoids, polyps, fissures, fistulas, and abscesses

34. Sigmoidoscopy • Uses a sigmoidoscope to view the lower portion of the sigmoid colon and the rectum • This exam aids in the diagnosis of inflammation, infection, or ulcerative conditions.

35. Ultrasound • Uses high-frequency sound waves directed toward the liver, gallbladder, or pancreas • Especially useful when liver and gallbladder functions are impaired and the use of contrast media is ineffective

36. Anorectal Abscess and Fistula • This localized infection is a collection of exudate in the soft tissue adjacent to the anus or rectum. • Characterized by a throbbing, painful lump, which makes sitting and coughing very uncomfortable

37. Appendicitis and Cirrhosis • Appendicitis • An acute inflammation of the appendix • Cirrhosis • Chronic liver disease that causes destruction of liver cells • Destruction leads to impaired blood and lymph circulation; interferes with the life-preserving functions of the liver

38. Colitis and Colostomy • Colitis • Inflammation of the colon; causes tenderness and discomfort • Colostomy • Surgical creation of an artificial opening of the colon, allowing fecal material to be excreted from the body through the abdominal wall

39. Colorectal Cancer and Constipation • Colorectal cancer • Malignancy of the colon or rectum • Constipation • Sluggish bowel action that results in dry, hard, infrequent bowel movements

40. Crohn’s Disease and Diarrhea • Crohn’s disease • Inflammation of any portion of the GI tract • Diarrhea • Repeated passage of unformed waste characterized by frequent, liquid stools

41. Diverticulosis and Esophageal Varices • Diverticulosis • Presence of bulging pouches in the walls of the GI tract where the lining has pushed into the surrounding muscle • Esophageal varices • Dilated, tortuous veins in the lower section of the esophagus that result in fluids entering the abdominal cavity

42. Fissure of the Anus and Gastroenteritis • Anal fissure • Crack or tear in the lining of the anus • Gastroenteritis • Inflammation of the stomach and intestines that causes fever, nausea, abdominal cramping, diarrhea, and vomiting

43. Gastroesophageal Reflux Disease and Hemorrhoids • Gastroesophageal reflux disease (GERD) • Results from a backflow of gastric and sometimes duodenal contents into the esophagus through the sphincter just above the stomach • Hemorrhoids • Veins in the mucosa of the folds of the anal canal frequently become dilated, causing them to bulge or protrude outside the body

44. Hepatitis • Liver infection that can result in cell destruction and death • Type A • Transmitted through the fecal-oral route when waste organisms get into food • Type B • Transmitted through blood and sexual contact with an infected person

45. Hepatitis • Type C • Acquired through blood and body fluids

46. Hernia • Protrusion of an internal organ through a natural opening in the body wall • Hiatal hernia • A portion of the stomach slips through the diaphragmatic opening at the end of the esophagus • Inguinal hernia • Spermatic cords pass through the lower abdominal walls

47. Common Sites of Hernia

48. Ileostomy • Surgical opening of the ileum to allow the chyme of the small intestine to empty through the abdominal wall

49. Irritable Bowel Syndrome • Chronic or periodic diarrhea and alternating constipation • This condition is also called spastic colon.

50. Oral Cancer • About 90% of oral cancers are squamous cell cancers that develop in the tissue linings of the mouth, lip, tongue, and throat. • The use of snuff or tobacco, alcohol abuse, and overexposure to the sun are the primary risk factors for oral cancers.