1. The Digestive System and Nutrition
Chapter 14 Canale MVCC

2. Digestive System Figure 14.1 ACCESSORY ORGANS: Salivary glands
• Saliva moistens food
• Bicarbonate maintains pH
• Amylase digests starch
• Lysozyme inhibits bacteria
Liver
• Produces bile
• Performs various functions associated with processing and storing nutrients
Pancreas
• Secretes digestive enzymes into small intestine
• Secretes bicarbonate into small intestine to neutralize stomach acid
Gallbladder
• Stores and concentrates bile
Appendix • No known digestive function
Pharynx
• Passageway for food and air
• Participates in swallowing
Esophagus
• Moves food from pharynx to stomach
Mouth
• Teeth chew food
• Tongue positions and tastes food
ORGANS:
Stomach
• Stores and mixes food
• Begins chemical digestion of protein by enzymes and acid
• Regulates delivery to the small intestine
Anus
• Expels undigested material
Rectum
• Passageway for feces
Sigmoid colon • Stores feces
Large intestine
• Absorbs the last of the water and nutrients
• Stores waste material
Small intestine
• Digests proteins, fats, and carbohydrates
• Absorbs most of the water and nutrients
• Secretes digestive hormones and enzymes
Figure 14.1

3. Gastrointestinal (GI) Tract Layers
Structure
Common layers throughout the system
Mucosa - Mucous membrane layer. Lines the digestive tract.
Submucosa - Connective tissue layer. Contains blood vessels, lymph vessels, and nerves
Muscularis - Two layers of smooth muscle. Responsible for motility of the digestive tract
Serosa - Connective tissue outer covering . Protects and anchors the digestive tract
Animation—The Digestive System

4. Gastrointestinal (GI) Tract Wall
Lymph vessel
Vein
Lumen
Circular layer
Longitudinal layer
Serosa
• Connective tissue outer covering
• Protects and anchors the digestive tract
Mucosa
• Mucous membrane layer
• Lines the digestive tract
Submucosa
• Connective tissue layer
• Contains blood vessels, lymph vessels, and nerves
Muscularis
• Two layers of smooth muscle
• Responsible for motility of the digestive tract
Artery
Nerve
Gastrointestinal (GI) Tract Wall
Figure 14.2

5. Digestive System Processes
Five processes
Mechanical processing and movement
chewing and mixing
Secretion
Fluid
Digestive enzymes and hormones
Bile, acid, alkali, mucus

6. Digestive System Processes
Five processes (continued)
Digestion
Breaking down food to smallest absorbable units
Absorption
Through mucosa
Into blood or lymph vessels for transport via circulation.
Elimination
Undigested material eliminated

7. Motility: Peristalsis – smooth muscle contractions
Figure 14.3a

8. Motility: Segmentation
Figure 14.3b

9. The Mouth: Teeth
Figure 14.4a–b

10. The Mouth: mechanical and chemical digestion
The mouth begins digestion
Teeth
Types: incisors, canines, premolars, molars
Structure: crown, root
Mechanical digestion – increases surface area of food
Tongue
Skeletal muscle
Moves food in mouth
Taste – sweet, bitter, hot/spicey

11. The Mouth Saliva – chemical digestion Salivary glands located:
Parotid – side of face
Submandibular – lower jaw
Sublingual - under tongue
Composition
Mucin, salivary amylase, bicarbonate, lysozyme
Begins the break down of carbohydrates from polysaccharides to disaccharides

12. Salivary Glands
Figure 14.5

13. Swallowing: Voluntary phase: Tongue pushes bolus of food into pharynx
Figure 14.6a

14. Swallowing: Delivers Food to Stomach
Involuntary phase/swallowing reflex
Receptors in pharynx stimulated by presence of food
Soft palate rises
Larynx rises slightly
Epiglottis closes opening to trachea
Tongue pushes food further
Food enters esophagus

15. Swallowing
Figure 14.6b

16. Pharynx and Esophagus Pharynx Esophagus
Common passageway for air and food
Participates in swallowing
Esophagus
Connects pharynx to stomach
A mix of skeletal and smooth muscle
Mucus-secreting cells assist passage of food
Food motility
Gravity and peristalsis

17. Structure of the Stomach Wall
Figure 14.7a–b

18. Stomach Function Food storage Digestion Regulation of delivery
Held and digested and then slowly released into the small intestine.
Digestion
Mechanical and chemical digestion
Digestion of carbohydrates, proteins and fats
Regulation of delivery
Slowly releases food into small intestines (allows for optimal absorption).

19. Stomach Function Specific cells secrete gastric juice Intrinsic factor
Hydrochloric acid
Produces a pH of about 2; breaks down large bits of food
Intrinsic factor
Made by same cells that make acid; needed to absorb vitamin B12
Mucus
Secreted by cells that line the stomach
Protects stomach lining from acid
Pepsin - enzyme
HCL activates pepsin – to begin breakdown of proteins.

20. The Stomach
Figure 14.7

21. Stomach Contraction: blends food – mechanical digestion
Movement = propels forward into small intestine
Direction: from lower esophageal sphincter to pyloric sphincter
Chyme: result of mixing; affects hormone secretions, regulating peristalsis and emptying of stomach

22. Peristalsis
Figure 14.8

23. Small Intestine Functions Digestion Absorption!!!
Neutralizes acid from stomach
Adds digestive enzymes and bile
Breaks proteins, carbohydrates, and lipids to absorbable materials (simple molecules – so they can enter cells).
Absorption!!!
95% of food absorbed in small intestine

24. Small Intestine Structure Regions Mucosa adaptations
Duodenum – portion after stomach
Jejunum – middle small intestines
Ileum – part before the
Mucosa adaptations
Villi containing blood and lacteal capillaries
Increase surface area – maximum absorption!!

25. The Wall of the Small Intestine
Figure 14.9a–b

26. The Wall of the Small Intestine
Figure 14.9c

27. Major Digestive Enzymes
Table 14.1

28. Accessory Organs: Aid Digestion and Absorption - (food does not enter
Pancreas
Exocrine functions – released through ducts
Secretes digestive enzymes
Amylase – carbohydrates
Trypsin – proteins
Secretes sodium bicarbonate – neutralize acid

29. Accessory Organs: Aid Digestion and Absorption
Liver
Produces bile
Bile stored in gull bladder and secreted into small intestine
Digests lipids – gives feces a brown color
Hepatic portal system
Drains blood from the digestive tract to the liver
Metabolic functions
Storage, synthesis, and chemical processing

30. • Stores and concentrates bile
Liver
• Produces bile (water and electrolytes, cholesterol, bile salts, lecithin, and pigments)
Esophagus
Stomach
Common bile duct
Pancreatic duct
Gallbladder
• Stores and concentrates bile
• Delivers bile to the duodenum via the common bile duct
Pancreas
• Secretes enzymes (proteases, amylase, lipase)
• Produces sodium bicarbonate
• Delivers these products to the duodenum via ducts
Duodenum
Figure 14.10

31. Accessory Organs: Aid Digestion and Absorption
Figure 14.11

32. Large Intestine: Structure and Function
Functions
Absorbs nutrients and water
Eliminates waste
Structure
Cecum - receives chyme from small intestines
appendix – evolutionary function
Colon
Ascending, transverse, descending, sigmoid

33. Rectum - when food enters and is stretched a neural reflext causes the internal sphincter to relax and the rectum to contract. Potty training is learning conscious control of this sphincter. Anus - exit

34. Large Intestine Transverse colon Ascending colon Descending colon
Small intestine
Ileocecal valve
Cecum
Appendix
Sigmoid colon
Rectum
External anal sphincter (skeletal muscle)
Internal anal sphincter (smooth muscle)
Anus
Anal canal
Figure 14.12

35. Absorption of Nutrients
Proteins and carbohydrates
Active transport – requires ATP!
Lipids
Broken down and reassembled
Water
Osmosis - disruption can lead to constipation or diarrhea
Vitamins and minerals
Assorted means

36. Absorption of Proteins and Carbohydrates
Figure 14.13

37. Endocrine and Nervous Systems Regulation of Digestion
Regulation dependent on volume and content of food
Nervous system
Stretch receptors in stomach – send signal to hypothalamus telling our body whether we are hungry or not. (hunger is different than appetite)
Hormones
Gastrin
Secretin
Cholecystokinin (CCK)

38. Absorption of Fats
Figure 14.14

39. Endocrine and Nervous Systems Regulation of Digestion
Gastrin
Stimulates release of gastric juice –
Excreted when the NS gets a signal from stretch receptors in stomach that food is present.
Stimulates large intestine motility
Secretin
Stimulates pancreas to secrete water and bicarbonate (neutralizes acide)
Occurs when duodenum is stretched
Slows peristalsis in stomach
Cholecystokinin (CCK)
Signals pancreas to secrete digestive enzymes
Signals gall bladder to release bile

40. Nutrients: Utilized or Stored Until Needed
Figure 14.15

41. Food Guide Pyramid
Figure 14.16

42. Nutrition Carbohydrates Major energy source Simple or complex Lipids
Cell components and energy sources
Saturated, unsaturated, and trans fats
Proteins
20 amino acids (8 essential )
Vitamins
Fat soluble and water soluble
Minerals
Recommended daily allowance
Fiber
Benefits colon

43. Weight Control: Energy Consumed Versus Energy Spent
Basic Metabolic Rate (BMR)
Number of calories needed at rest
Influencing factors
Gender, body composition, age, health, stress, food intake, genetics

44. Weight Control: Energy Consumed Versus Energy Spent
Energy balance and body weight
Caloric content
Fat = 9 calories
Proteins and sugars = 4 calories
Excess intake leads to increased storage (weight)
Physical activity
Uses calories
Healthy weight improves health

45. Disorders of the Digestive System
Disorders of the GI tract
Lactose intolerance
Diverticulosis
Colon polyps
Disorders of accessory organs
Hepatitis
Gallstones
Malnutrition
Obesity
Pandemic
Eating disorders
Anorexia nervosa
Bulimia