1. The Digestive System

2. Day 1

3. The Digestive System and Body Metabolism
Digestion
Breakdown of ingested food
Absorption of nutrients into the blood
Metabolism
Production of cellular energy (ATP)
Constructive and degradative cellular activities

4. Organs of the Digestive System
Two main groups:
Alimentary canal or
Gastrointestinal tract (GI tract)
- continuous coiled hollow tube
2. Accessory digestive organs

5. Organs of the Digestive System
Figure 14.1

6. Organs of the Alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus

7. McGraw-Hill Digestive System Video (Click Link)

8. Mouth (Oral Cavity) Anatomy
Lip (labia) – protect the anterior opening
Cheeks – form the lateral walls
Hard palate – forms the anterior roof
Soft palate – forms the posterior roof
Uvula – fleshy projection of the soft palate
Frenulum is a fold of mucous membranes that secures the tongue to the floor and limits its posterior movements
Figure 14.2a

9. Mouth (Oral Cavity) Anatomy
Vestibule – space between lips externally and teeth and gums internally
Oral cavity – area contained by the teeth
Tongue – attached at hyoid and styloid processes of the skull, and by the lingual frenulum
Figure 14.2a

10. Mouth (Oral Cavity) Anatomy
Tonsils are part of the body’s defense system
When the tonsils are inflamed and enlarged, they block the entrance to the throat, making swallowing difficult
Tonsils are found in the posterior end of the oral cavity
Palatine tonsils
Lingual tonsil
Figure 14.2a

11. Mastication (chewing) of food Mixing masticated food with saliva
Functions of the Mouth
Mastication (chewing) of food
Mixing masticated food with saliva
Initiation of swallowing by the tongue
Allowing for the sense of taste

12. Digestive Activities of the Mouth
Mechanical digestion
Food is physically broken down by chewing
Chemical digestion
Food is mixed with saliva
Breaking of starch into maltose by salivary amylase

13. Pharynx (Throat) Anatomy
Nasopharynx – not part of the digestive system
Oropharynx – posterior to oral cavity
Laryngopharynx – below the oropharynx and connected to the esophagus
Figure 14.2a

14. Pharynx Function Serves as a passageway for AIR AND FOOD
Food is propelled to the esophagus by two muscle layers
Longitudinal inner layer
Circular outer layer
Food movement happens by alternating contractions of the muscle layers (peristalsis)

15. Esophagus Also called the gullet
Runs from pharynx to stomach through the diaphragm
Conducts food by peristalsis (slow rhythmic squeezing)
Passageway for FOOD ONLY (respiratory system branches off after the pharynx)

16. Activities of the Pharynx & Esophagus
These organs have
NO DIGESTIVE FUNCTION!!
Serve as passageways to the stomach
Propulsion: swallowing & peristalsis

17. Deglutition (Swallowing)
Figure 14.14

19. Day 2

20. Located on the left side of the abdominal cavity
Stomach Anatomy
C-shaped
Located on the left side of the abdominal cavity
nearly hidden by the liver and diaphragm
Cardioesophageal Sphincter
Where food enters

21. Food empties into the small intestine at the pyloric sphincter
Stomach Anatomy
Regions of the stomach
1. Cardiac region
2. Fundus
3. Body
4. Pylorus
funnel-shaped terminal end
Food empties into the small intestine at the pyloric sphincter

22. Stomach Anatomy Rugae External regions internal folds of the mucosa
Lesser curvature
Greater curvature

23. Stomach Anatomy
After food has been processed, it looks like a heavy cream, and is called chyme
Delivers chyme to the small intestine through the pyloric sphincter

24. Stomach Anatomy
Figure 14.4a

25. Acts as a storage tank for food Site of food breakdown
Stomach Functions
Because of muscle, the food can move, but also churn, mix, and pummel food, breaking it into smaller particles
Acts as a storage tank for food
Site of food breakdown
Chemical breakdown of protein begins

26. Digestion and Absorption in the Stomach
Protein digestion enzymes
Pepsin – an active protein digesting enzyme
Rennin – works on digesting milk protein
The only absorption that occurs in the stomach is of alcohol and aspirin

27. Propulsion in the Stomach
Food must first be well mixed
Rippling peristalsis occurs in the lower stomach
The stomach empties in four to six hours
Figure 14.15

28. Food Breakdown in the Stomach
Gastric juice is regulated by neural and hormonal factors
Presence of food or falling pH causes the release of gastrin
Gastrin causes stomach glands to produce protein-digesting enzymes
Hydrocholoric acid makes the stomach contents very acidic

29. Full – it can hold 4L or 1 gallon of food
Stomach Facts
Full – it can hold 4L or 1 gallon of food
Empty – it collapses in on itself, mucosa forms folds called rugae

30. The body’s major digestive organ
Small Intestine
The body’s major digestive organ
Site of nutrient absorption into the blood

31. Small Intestine
Muscular tube extending from the pyloric sphincter to the ileocecal valve
Suspended from the posterior abdominal wall by the mesentery
Longest section of the alimentary canal and average length is 7 feet-18 feet!

32. Subdivisions of the Small Intestine
Duodenum
Attached to the stomach
Curves around the head of the pancreas
Jejunum
Attaches anteriorly to the duodenum
Ileum
Extends from jejunum to large intestine

33. Chemical Digestion in the Small Intestine
Source of enzymes that are mixed with chyme
Intestinal cells
Pancreas
Bile enters from the gall bladder

34. Chemical Digestion in the Small Intestine
Figure 14.6

35. Villi & Microvilli of the Small Intestine
Fingerlike structures formed by the mucosa
Give the small intestine more surface area
MICROVILLI
Small projections of the plasma membrane
Found on absorptive cells
Figure 14.7a

36. Structures Involved (in Absorption of Nutrients):
Absorptive cells
Blood capillaries
Lacteals
Figure 14.7b

37. Digestion in the Small Intestine
Enzymes from the brush border
Break double sugars into simple sugars
Complete some protein digestion

38. Pancreatic enzymes play the major digestive function
Help complete digestion of starch
Carry out about half of all protein
Responsible for fat digestion
Digest nucleic acids

39. Not in the notes…. Will resume next slide

40. Absorption in the Small Intestine
Water is absorbed along the length of the small intestine
End products of digestion
Most substances are absorbed by active transport through cell membranes
Lipids are absorbed by diffusion
Substances are transported to the liver by the hepatic portal vein or lymph

41. Propulsion in the Small Intestine
Peristalsis is the major means of moving food
Segmental movements
Mix chyme with digestive juices
Aid in propelling food

42. Large Intestine
Larger in diameter, but shorter than the small intestine
Frames the internal abdomen
Average length is 1.5m or 5 feet long
It extends from the ileocecal valve to the anus

43. Structures of the Large Intestine
Cecum – saclike first part of the large intestine
Appendix
Hangs from the cecum
Bacteria can accumulate and multiply here causing appendicitis, inflammation of the appendix
Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)

44. Structures of the Large Intestine
Colon
1. Ascending - travels up the right side of the abdominal cavity and turns
2. Transverse - continues after the turn
3. Descending - continues down the left side
4. S-shaped sigmoidal - enters the pelvis and is s-shaped
5. Rectum

45. Anal sphincter or canal
Anus - External body opening
The anal canal has an external voluntary sphincter composed of skeletal muscle
It also has an internal involuntary sphincter formed by smooth muscle
These sphincters act to open and close
Closed most of the time, it is only open during defecation, when feces are eliminated from the body
Large intestine contains goblet cells that produce mucus to act as a lubricant to ease the passage of feces
2. Sigmoid colon, rectum, and anus lie in the pelvic region

46. Functions of the Large Intestine
Absorption of water
Eliminates indigestible food from the body as feces
Does not participate in digestion of food
Goblet cells produce mucus to act as a lubricant

47. Food Breakdown and Absorption in the Large Intestine
No digestive enzymes are produced
Resident bacteria digest remaining nutrients
Produce some vitamin K and B
Release gases
Water and vitamins K and B are absorbed
Remaining materials are eliminated via feces

48. Propulsion in the Large Intestine
Sluggish peristalsis
Mass movements
Slow, powerful movements
Occur three to four times per day
Presence of feces in the rectum causes a defecation reflex
Internal anal sphincter is relaxed
Defecation occurs with relaxation of the voluntary (external) anal sphincter

52. Day 3

53. Accessory Digestive Organs
Salivary glands
Teeth
Pancreas
Liver
Gall bladder

54. Salivary Glands Saliva-producing glands
Parotid glands – located anterior to ears, becomes inflamed with the mumps
Submandibular glands
Sublingual glands

55. Saliva Mixture of mucus and serous fluids Helps to form a food bolus
Contains salivary amylase to begin starch digestion
Dissolves chemicals so they can be tasted

56. Teeth The role is to masticate (chew) food
Humans have two sets of teeth
Deciduous (baby or milk) teeth
20 teeth are fully formed by age two

57. Teeth Permanent teeth Classification
Replace deciduous teeth beginning between the ages of 6 to 12
A full set is 32 teeth, but some people do not have wisdom teeth
Classification
Incisors, Canines, Premolars, Molars

58. Pancreas
Produces a wide spectrum of digestive enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Alkaline fluid introduced with enzymes neutralizes acidic chyme
Endocrine products of pancreas
Insulin
Glucagons

59. Liver Largest gland in the body
Located on the right side of the body under the diaphragm
Has many functions, its digestive function is to produce bile
Connected to the gall bladder via the common hepatic duct

60. Bile Produced by cells in the liver Composition Bile salts
Bile pigment (mostly bilirubin from the breakdown of hemoglobin)
Cholesterol
Phospholipids
Electrolytes

61. Liver conditions Hepatitis – inflammation of the liver
– caused by viral infection
Cirrhosis
– inflammatory condition in which liver is severely damaged and becomes hard and fibrous
Likely when someone drinks alcohol excessively for many years

62. Gall Bladder
Small, thin-walled green sac that fits in a shallow fossa in the inferior surface of the liver
It stores bile and removes water
When fatty foods enter the duodenum, a hormone prompts the gallbladder to contract and spurt out stored bile
If bile is stored for too long or too much water is removed, the cholesterol it contains may crystallize and form gallstones
Gallstones are sharp, and when the gallbladder contracts it causes extreme pain or a gallbladder attack

63. Processes of the Digestive System
1. Ingestion – getting food into the mouth 2. Propulsion – moving foods from one region of the digestive system to another

64. Processes of the Digestive System
3. Peristalsis – alternating waves of contraction 4. Segmentation - moving materials back and forth to aid in mixing
Figure 14.12

65. Processes of the Digestive System
5. Mechanical digestion
Mixing of food in the mouth by the tongue
Churning of food in the stomach
Segmentation in the small intestine

66. Processes of the Digestive System
6. Chemical Digestion
Enzymes break down food molecules into their building blocks
Each major food group uses different enzymes
Carbohydrates are broken to simple sugars
Proteins are broken to amino acids
Fats are broken to fatty acids and alcohols

67. Processes of the Digestive System
7. Absorption
End products of digestion are absorbed in the blood or lymph
Food must enter mucosal cells and then into blood or lymph capillaries
8. Defecation
Elimination of indigestible substances as feces

68. Processes of the Digestive System
Figure 14.11

69. Nutrition 1. Carbohydrates 2. Lipids 3. Proteins 4. Vitamins
Nutrient – substance used by the body for growth, maintenance, and repair
Categories of nutrients
1. Carbohydrates
2. Lipids
3. Proteins
4. Vitamins
5. Mineral
6. Water

70. Dietary Sources of Major Nutrients
1. Carbohydrates
Most are derived from plants
Exceptions: lactose from milk and small amounts of glycogens from meats
2. Lipids
Saturated fats from animal products
Unsaturated fats from nuts, seeds, and vegetable oils
Cholesterol from egg yolk, meats, and milk products

71. 3. Proteins
Complete proteins – contain all essential amino acids
Most are from animal products
Legumes and beans also have proteins, but are incomplete
4. Vitamins
Most vitamins are used as cofactors and act with enzymes
Found in all major food groups

72. 5. Minerals
Play many roles in the body
Most mineral-rich foods are vegetables, legumes, milk, and some meats

73. Metabolism Chemical reactions necessary to maintain life
Catabolism – substances are broken down to simpler substances
Anabolism – larger molecules are built from smaller ones
Energy is released during catabolism

74. Developmental Aspects of the Digestive System
Teething begins around age six months
Metabolism decreases with old age
Middle age digestive problems
Ulcers
Gall bladder problems

75. Developmental Aspects of the Digestive System
Activity of digestive tract in old age
Fewer digestive juices
Peristalsis slows
Diverticulosis and cancer are more common