1. The Digestive System Objectives
31-1 Spell, define, and correctly use the Key Terms in this chapter.
31-2 List the functions of the digestive system.
31-3 Trace the pathway of food through the alimentary canal.
31-4 Describe the structure and functions of the mouth, teeth, tongue, and salivary glands.
31-5 Describe the structure and function of the pharynx.

2. The Digestive System Objectives (cont.)
31-6 Describe the swallowing process.
31-7 Describe the structure of the esophagus and tell how it propels food into the stomach.
31-8 Describe the structure and functions of the stomach.
31-9 List the substances secreted by the stomach and give their functions.
31-10 Describe the structure and functions of the small intestine.

3. The Digestive System Objectives (cont.)
31-11 List the substances secreted by the small intestine and describe the importance of each.
31-12 Explain the structures and functions of the liver, gallbladder, and pancreas.
31-13 List the substances released by the liver, gallbladder, and pancreas into the small intestine and give the function of each secretion.

4. The Digestive System Objectives (cont.)
31-14 Describe the structure and functions of the large intestine.
31-15 Tell what types of nutrients are absorbed by the digestive system and where they are absorbed.
31-16 Describe the signs, symptoms, causes, and treatments of various disorders and diseases of the digestive system.

5. Introduction Digestion Two categories
The mechanical and chemical breakdown of foods into forms that your body cells can absorb
The organs of the digestive system carry out digestion.
Two categories
Those of the alimentary canal
The accessory organs

6. Alimentary Canal
Length of the entire canal is about 9 meters (29 feet)
Mucosa - absorbs nutrients
Submucosa - carry away absorbed nutrients
Muscular layer - move materials through the canal
Serosa - secretes serous fluid to keep the outside of the canal moist and prevent it from sticking to other organs.

7. Mouth, Teeth, Tongue, and Salivary Glands
Mouth takes in food and reduces its size through chewing
Salivary glands - saliva (spit) contains an enzyme that will break down carbohydrates 
Teeth act to decrease the size of food particles and different types of teeth are adapted to handle food in different ways

8. Apply Your Knowledge
What is the purpose of the serosa?

9. Apply Your Knowledge -Answer
What is the purpose of the serosa?
Serosa - secretes serous fluid to keep the outside of the alimentary canal moist and prevent it from sticking to other organs.

10. Pharynx
The throat - long, muscular structure that extends from the area behind the nose to the esophagus
Nasopharynx
Oropharynx
Laryngopharynx
Acts to connect the nasal cavity with the oral cavity for breathing through the nose
Acts to push food into the esophagus

11. Swallowing Process An involuntary automatic response (reflex)
Soft palate raises causing the uvula to cover the opening between the nasal cavity and oral cavity
Epiglottis covers the opening of the larynx

12. Swallowing Process (cont.)
Muscles in the pharynx contract, forcing food toward the esophagus
Esophagus opens
Food is pushed into the esophagus by the muscles of the pharynx

13. Esophagus
Esophagus is a muscular tube about 25 cm long that connects the pharynx to the stomach
Esophageal sphincter controls the movement of food into the stomach
Opens and closes to allow or prevent movement of substances out of a tube

14. Stomach
Below the diaphragm in the upper left region of the abdominal cavity
It functions to receive food from the esophagus
Mix food with gastric juice (secretions of the stomach lining)
Start protein digestion
Move food into the small intestine
Click for Larger View

15. Stomach (cont.)

16. Stomach Secretions
When a person smells, tastes, or sees appetizing food, the parasympathetic nervous system stimulates the gastric glands to secrete their products.
Gastrin, made by the stomach, also stimulates gastric glands to become active.
Chief cells - secrete pepsinogen, which becomes pepsin in the presence of acid. Pepsin digests proteins.

17. Stomach Secretions (cont.)
Parietal cells –
secrete hydrochloric acid, that convert pepsinogen to pepsin.
secrete intrinsic factor, which is necessary for vitamin B12 absorption.

18. Small Intestine
Small intestine is a tubular organ that extends from the stomach to the large intestine
Carries out most digestion in the body and is responsible for absorbing most of the nutrients into the bloodstream

19. Small Intestine - Secretions
Peptidases - enzymes that digest proteins.
Intestinal lipase - an enzyme that digests fats
Sucrase, maltase, and lactase - Digest sugars.
If a person cannot produce lactase, he will not be able to digest lactose, which is the sugar in dairy products - lactose intolerance

20. Apply Your Knowledge Your patients states that she is lactose
intolerant. What does that mean?

21. Apply Your Knowledge -Answer
Your patient states that she is lactose
intolerant. What does that mean?
She cannot produce lactase and cannot digest lactose, which is the sugar in dairy products; thus, she is lactose intolerant.

22. Pancreas Pancreas is located behind the stomach.
Pancreatic acinar cells produce pancreatic juice.
Pancreatic juice contains the following enzymes:
Pancreatic amylase - digests carbohydrates
Pancreatic lipase - digests lipids
Nucleases - digests nucleic acids
Trypsin, chymotrypsin, and carboxypeptidase - digest proteins

23. Liver Reddish-brown in color
Large organ that fills most of the upper right abdominal quadrant
Has a large right lobe and a small left lobe - separated into smaller divisions called hepatic lobules. Hepatic lobules contain macrophages that destroy bacteria and viruses in the blood
Stores vitamins and iron

24. Liver (cont.)
Each hepatic lobule contains many cells called hepatocytes
Process the nutrients in blood and make bile, which is used in the digestion of fats
Bile leaves the liver through the hepatic duct

25. Gallbladder Gallbladder
Small sac-like structure located beneath the liver
Only function is to store bile
Cholecystokinin causes the gallbladder to release bile
Gallbladder

26. Large Intestine
Large intestine extends from the ileum of the small intestine to where it opens to the outside world as the anus

27. Large Intestine (cont.)
Lining of the large intestine - secretes mucus to aid in the movement of substances
Large intestine absorbs water and a few electrolytes from chyme; the left over forms feces

28. The Absorption of Nutrients
Nutrients are defined as necessary food substances and are absorbed in the small intestine
Carbohydrate
Proteins
Lipids
Vitamins
Minerals
Water

29. Apply Your Knowledge
Why can a person live without their gallbladder?

30. Apply Your Knowledge -Answer
Why can a person live without their gallbladder?
It’s only purpose is to store bile. As long as a person is still making bile in the liver, they can still digest fats.

31. Diseases and Disorders of the Digestive System
Appendicitis - an inflammation of the appendix
Causes
Blockage of appendix with feces
Blockage of appendix with tumor
Treatments
Surgery to remove appendix
Antibiotics to prevent infection
Signs and symptoms – lack of appetite, pain in and around the navel area or in the abdomen, nausea, slight fever, pain in the right leg, and increased white blood cell content

32. Diseases and Disorders of the Digestive System
Cirrhosis - a long lasting liver disease in which normal liver tissue is replaced with nonfunctional scar tissue
Causes - Excessive alcohol consumption
Hepatitis C infection
Hepatitis B infection
Treatment - Liver transplant
Lifestyle changes to stop medications or use of alcohol

33. Cirrhosis

34. Diseases and Disorders of the Digestive System (cont.)
Colitis - defined as inflammation of the large intestine
Causes - caused by viral or bacterial infection or the use of antibiotics. Ulcers in the large intestine, Crohn’s disease, various other diseases, and stress may contribute.
Treatments
Treating underlying causes
Changing antibiotics
Fluids
Repair of ulcers

35. Colitis

36. Diseases and Disorders of the Digestive System (cont.)
Colorectal cancer usually comes from the lining of the rectum or colon.
Causes - mostly unknown. Polyps in colon or rectum can become cancerous.
Signs
Changes in bowel movement
Blood in feces
Anemia
Abdominal pain
Weight loss
Narrow feces

37. Colorectal Cancer

38. Diseases and Disorders of the Digestive System (cont.)
Crohn’s disease - a common type of inflammatory bowel disease and is an autoimmune disorder that typically affects the end of the small intestine
Causes - this is an autoimmune disorder.
Treatment
Medications to reduce inflammation
Antibiotics
Surgery to remove affected part of intestine
Changes in diet

39. Chrohn’s Disease

40. Diseases and Disorders of the Digestive System (cont.)
Diverticulitis - inflammation of diverticuli in the intestine. Diverticuli are abnormal dilations in the intestinal wall
Causes – mostly unknown. Lack of fiber in diet and bacterial infection of the diverticuli.
Signs
Abdominal pain
Constipation
Diarrhea & nausea
Fever
Blood in feces
High white blood cell count

41. Diverticulitis

42. Diseases and Disorders of the Digestive System (cont.)
Gastritis - an inflammation of the stomach lining
Causes - bacteria or viruses, some medications, alcohol, spicy foods, excessive eating poisons, and stress.
Treatment
Cook food properly to kill bacteria/viruses
Avoid foods/medications that irritate stomach linings
Begin acid reducing medications

43. Gastritis

44. Diseases and Disorders of the Digestive System (cont.)
Heartburn - called gastroesophageal reflux disease (GERD) - occurs when stomach acids are pushed into the esophagus
Causes – alcohol, some foods, defective esophageal sphincter, pregnancy, obesity, hiatal hernia, and repeated vomiting.
Treatment
Reducing weight
Diet changes
Reduce alcohol consumption
Medications
Not lying down after meal

45. Heartburn

46. Diseases and Disorders of the Digestive System (cont.)
Hemorrhoids - varicose veins of the rectum or anus
Causes – constipation, excessive straining during bowel movements, liver disease, pregnancy, and obesity.
Treatment
Eating high fiber
Stool softeners
Medications
Surgery

47. Hemorrhoids

48. Diseases and Disorders of the Digestive System (cont.)
Hepatitis - inflammation of the liver.
Causes - bacteria, viruses, parasites, immune disorders, the use of alcohol and drugs, and overdose of acetaminophen.
Treatment
Avoid drugs and alcohol
Prescribed medications

49. Hepatitis

50. Diseases and Disorders of the Digestive System (cont.)
Hiatal hernia - occurs when a portion of the stomach protrudes into the chest through an opening in the diaphragm.
Inguinal hernias - occurs when a portion of the large intestine protrudes into the inguinal canal.
Oral cancer - usually involves the lips or tongue, but can occur anywhere in the mouth.
Pancreatic cancer – 4th leading cause of death in the U.S.
Stomach cancer - most common in the upper part of the stomach.
Stomach ulcers - occur in the lining of the stomach

51. Apply Your Knowledge
Your patient has been diagnosed with Crohn’s disease. What is the usual treatment for this disease?

52. Apply Your Knowledge -Answer
Your patient has been diagnosed with Crohn’s disease. What is the usual treatment for this disease?
Treatment for Crohn’s disease includes medications to reduce inflammation, antibiotics, surgery to remove affected part of intestine and/or changes in diet

53. Medical Assistant Summary
Knowledge of the digestive system will assist you in providing care for the patient with diseases and disorders of the digestive system.

54. End of Chapter
End of Chapter