1. The Digestive System Lesson 1:30
The Digestive System
Lesson 1:

2. Lesson Objectives
Upon completion of this lesson, students should be able to …
Define and spell the terms to learn for this chapter.
Describe the purpose and function of the digestive system.
Identify the primary organs of the digestive system and briefly explain the function of each.

3. Lesson Objectives Explain the three main portions of a tooth.
Identify the accessory organs of the digestive system and briefly explain the function of each.

4. Digestive System Purpose: Three main functions: Anatomy: Digest food
Process food
Eliminate waste products
Three main functions:
Digestion
Absorption
Elimination
Anatomy:
Digestive Tract
Tube from mouth to anus
Accessory Organs
Glands 4

5. Digestive System 5

6. Critical Thinking Questions
What organs comprise the “tube” of the digestive system?
What are the accessory organs? 6

7. Organs of the Digestive System
The Tube:
Mouth and teeth
Pharynx
Esophagus
Small intestine
Large intestine
The Saclike Organ:
Stomach
Accessory Organs:
Salivary glands
Gallbladder
Liver
Pancreas 7

8. Organs of the Digestive System
The “Tube”:
Mouth and Teeth
Pharynx
Esophagus 8

9. Organs of the Digestive System
The Tube (continued):
Small intestine
Large intestine 9

10. Organs of the Digestive System
The Saclike Organ:
Stomach 10

11. Organs of the Digestive System
Accessory Organs:
Salivary Glands
Parotid
Submandibular
Sublingual
Gallbladder
Liver
Pancreas 11

12. Critical Thinking Questions
Which of the three digestive functions occurs in the mouth?
Which of the three digestive functions occurs in the small and large intestines?
Which of the three digestive functions occurs in the stomach?
How do the accessory organs contribute to digestion? 12

13. Functions of the Digestive System
Digestion
Process of breaking down food into substances useful to the body
Occurs in the mouth and the stomach
Facilitated by chemicals released by accessory organs
Absorption
Process of absorbing nutrients into the body
Occurs in intestines 13

14. Functions of the Digestive System
Elimination
Process of removing waste from the body
Occurs in large intestine 14

15. Structures of the Mouth (Oral Cavity)
Hard palate
Lips and cheeks
Tongue
Teeth
Gingivae (gums)
Salivary glands
Soft palate and Pharyngeal arches
Digestion starts in the mouth. Saliva and the grinding of food by the teeth begin the digestive process. 15

16. The Tongue Skeletal muscle covered with a mucous membrane
Can be divided into three areas:
The rear portion, called the root
The central body
The pointed tip 16

17. The Tongue
Papillae (elevations) and taste buds are located on the surface of the tongue
Sweet
Sour
Salt
Bitter 17

18. Critical Thinking Question
How do these four types of taste buds produce the many flavors of our food? 18

19. The Teeth Humans have two sets of teeth over the lifetime
Deciduous (baby) teeth
Permanent teeth 19

20. The Teeth Types of teeth Incisors Canines or cuspids
Premolars or bicuspids
Molars
Shapes of different types of teeth allow various functions in the digestive process 20

21. Critical Thinking Question
How does the shape of each tooth allow it to do a different job in the chewing process? 21

22. Types of Teeth 22

23. Deciduous and Permanent Teeth
28 deciduous (baby) teeth
8 incisors, 4 cuspids, 8 molars
Erupt between about 6 months and 2 ½ years of age
Begin to fall out at about 6 years of age
Replaced by permanent teeth
32 permanent teeth
8 incisors, 4 canines, 8 premolars, 12 molars
Erupt between about 6 and 21 years of age 23

24. Critical Thinking Question
If the deciduous teeth fall out, why is it important for young children to practice good dental hygiene? 24

25. Structures of a Tooth Crown Root Neck Portion above the gum
Portion embedded in the gums
Neck
Portion embedded in the top of the gum between the crown and the root 25

26. Anatomy of a Tooth – From Crown to Root
Enamel
Hardest part of tooth
Covers exposed part of crown
Cavities occur in the enamel of the tooth 26

27. Critical Thinking Questions
What structures are affected if a cavity in the enamel is left untreated and penetrates to the pulp of the tooth?
What is the result to the patient? 27

28. Anatomy of a Tooth – From Crown to Root
Dentin
Calcified, largely mineral tissue that forms the bulk of the tooth
Softer than enamel 28

29. Anatomy of a Tooth – From Crown to Root
Gingivae (gums)
Periodontal ligament
Fibers that anchor teeth to bony sockets in the maxillary bone and mandible 29

30. Anatomy of a Tooth – From Crown to Root
Cementum
Protective layer on dentin
Anchors the periodontal ligament 30

31. Critical Thinking Question
What is the result when gingivitis (gum disease) destroys these structures? 31

32. The Pharynx Lies posterior to the mouth
Beginning of the esophagus (tube to the stomach)
Also opens to the trachea (windpipe)
Reflexive action closes the trachea during swallowing 32

33. Critical Thinking Question
What happens when food accidentally goes into the trachea? 33

34. The Esophagus Tube leading from the pharynx to the stomach
Carries food to stomach
About 10 inches long
Wavelike muscular contractions called peristalsis move food to the stomach 34

35. The Stomach Hollow, saclike organ Can hold 1 – 1.5 liters
Secretes chemicals that aid in digestion
Processes food into a semiliquid state (chyme)
Prepares food for further digestion and absorption in the small intestine 35

36. Critical Thinking Question
What nutrient is digested in the stomach? 36

37. Anatomy of the Stomach 37

38. The Stomach Muscular Organ: 3 parts: Layers of smooth muscle
Muscle arrangement allows churning, mixing action
3 parts:
Fundus (upper)
Body (main)
Antrum (lower) 38

39. The Stomach Stomach lining: Chyme: Mucosa lining
Rugae – folds in mucosa
Glands secrete gastric juices and hydrochloric acid
Chyme:
Mixture of gastric juices and semi-digested food 39

40. Sphincters of the Stomach
Sphincters are:
Muscular valves
Allow flow of food in single direction
Stomach has 2 sphincters 40

41. Critical Thinking Question
What would happen without sphincters?
Which structure is faulty when acid reflux occurs? 41

42. Sphincters of the Stomach
Lower esophageal (also called cardiac) sphincter:
Between the esophagus and the top of the stomach
Keeps food from backing into the esophagus 42

43. Sphincters of the Stomach
Pyloric sphincter:
Between stomach and small intestine
Allows small amount of chyme into intestines at a time 43

44. The Stomach’s Role in Digestion
Controls secretion of gastric juices
Initiates protein digestion
Regulates churning and mixing action
Regulates passage of chyme into the small intestine
The churning and mixing action of the stomach grinds and mixes the food and is called stomach motility. 44

45. Try It For Yourself! Provide the term suggested by each definition.
Semiliquid substance consisting of partially digested food
Muscular valves; allow flow in one direction
Ridges on the stomach lining
Secreted by the stomach lining
Chyme
Sphincter
Rugae
Gastric juices
and hydrochloric acid 45

46. Try It For Yourself! Complete the sentences.
Partially digested food passes into the intestine through the ______.
The upper part of the stomach is the _____.
Food enters the stomach through the ______ ______ _____.
Pyloric sphincter
Lower esophageal
sphincter
Fundus 46

47. The Small Intestine Tube about 21 feet long and 1inch in diameter
Attaches to the stomach at the pyloric sphincter
Ends at the ileocecal orifice at the beginning of the large intestine 47

48. Critical Thinking Question
What nutrients are digested in the small intestine? 48

49. Sections of the Small Intestine
Duodenum
First 12 inches of small intestine
Mixes food with bile and pancreatic juices
Most breakdown of food in the small intestine happens here
Jejunum
About 8 feet long
Middle section of the small intestine 49

50. Sections of the Small Intestine
Ileum
About 12 feet long
Joins the small intestine to the large intestine at the ileocecal orifice 50

51. Gross Anatomy of the Small Intestine51

52. Try It For Yourself! Provide the term suggested by each definition.
The portion of the small intestine where most food breakdown takes place
Junction of small and large intestine
Duodenum
Ileocecal orifice 52

53. The Large Intestine Begins at the ileocecal orifice
About 5 feet long and 2.5 inches in diameter
Minimal digestion occurs
Function:
Complete digestion
Complete absorption
Propel and eliminate waste 53

54. Sections of the Large Intestine
Cecum
Pouch, about 3 inches long
Appendix is a small appendage attached to the cecum
Colon
Largest section
Several parts
Ascending colon
Transverse colon
Descending colon
Sigmoid Colon
Rectum and Anus
Eliminate waste 54

55. and move and eliminate waste
Try It For Yourself!
Complete the sentences.
The main functions of the large intestine are to ______, _____, and _____.
The first section of the large intestine that connects to the small intestine is the _____.
The other sections of the large intestine are the ______,______, and _____.
Complete digestion,
complete absorption,
and move and eliminate waste
Transverse colon
Descending colon
Sigmoid Colon
Cecum 55

56. The Accessory Organs
Salivary Glands
Gallbladder
Liver
Pancreas 56

57. Critical Thinking Question
What is the general function of the accessory organs? 57

58. Salivary Glands Three pairs Parotid glands Submandibular glands
Sublingual glands 58

59. Salivary Glands Produce saliva Secreted into mouth via ducts
Contains amylase, an enzyme that helps break down carbohydrates
Maintains optimal pH in mouth
Mixes with food
Produces a soft mass called a bolus
Begins the digestion process 59

60. Critical Thinking Question
How does maintaining an optimal pH in the mouth affect the teeth? 60

61. The Salivary Glands 61

62. parotid, submandibular, and sublingual
Try It For Yourself!
Complete each sentence.
Saliva mixes with food to form a _____.
The three salivary glands are the _____, _____, and _____.
Saliva enters the mouth via _____.
bolus
parotid, submandibular, and sublingual
ducts 62

63. The Liver Largest glandular organ Has role in metabolism of:
Carbohydrates
Converts glucose to glycogen
Stores glycogen
Fats
Proteins
Stores iron and several vitamins
Detoxifies the body from substances 63

64. Critical Thinking Question
What substances does the liver detoxify? 64

65. Products of the Liver Bile Fibrinogen and Prothrombin Heparin
Emulsifies fat before releasing the products into the bloodstream
Fibrinogen and Prothrombin
Essential for blood clotting
Heparin
Prevents the clotting of blood
Blood proteins
Albumin, gamma globulin
Although the liver has many functions, its primary role in digestion is to produce the bile that emulsifies fats. 65

66. The Liver 66

67. Try It For Yourself! Complete each sentence.
The liver’s primary digestive role is to _____ _____.
The liver has a role in the metabolism of _____, _____, and _____.
produce bile
carbohydrates,
proteins, and fats 67

68. The Gallbladder Membranous sac below the liver Stores bile
Concentrates bile
Bile stored in the gallbladder is six to ten times more concentrated than bile from the liver
Gallstones can form (cholelithiasis) and the gallbladder can become inflamed 68

69. Critical Thinking Question
How does the concentration of bile in the gallbladder contribute to the formation of gallstones? 69

70. The Gallbladder 70

71. The Pancreas Posterior to (behind) the stomach
About 6 to 9 inches long
Produces digestive enzymes
Serves endocrine function
Secretes insulin and glucagon
Regulates blood sugar levels 71

72. The Pancreas Part of two body systems: Function: Digestive Endocrine
To secrete the hormone insulin, which regulates blood sugar 72

73. The Pancreas 73

74. Try It For Yourself! Complete each sentence.
The pancreas is also part of the _____ _____.
The pancreas produces digestive _____.
endocrine system
enzymes 74

75. Questions? 75