Chapter 24



Chapter 24

THE DIGESTIVE SYSTEM

Outline and Objectives

INTRODUCTION

1. Define digestion and absorption and identify the system that provides these functions.

OVERVIEW OF THE DIGESTIVE SYSTEM

2. Identify the organs of the gastrointestinal tract and the accessory organs of digestion and their general functions in digestion and absorption of food molecules for use by body cells.

2. List and define the six primary processes of digestion performed by the gastrointestinal tract.

LAYERS OF THE GI TRACT

4. Name the four basic tissue layers of the GI tract that are commonly found from the stomach to the anus.

Mucosa

4. Discuss the characteristic structure and duties of the epithelial, lamina propria, and muscularis layers of the mucosa.

Submucosa

4. Describe the structural, neural, and secretory features of the submucosal layer.

Muscularis

5. Describe the muscle changes, layers, and control through the extent of the GI tract.

Serosa

6. Describe the serosa as a part of the peritoneum.

PERITONEUM

9. Discuss how the components of the peritoneal serosal membrane surround the abdominal organs and form the peritoneal cavity.

9. Describe the mesentery tissue and functions, and then the conspicuous folds that support the abdominal digestive organs.

10. Discuss the causes, symptoms, and seriousness of peritonitis.

MOUTH

12. Discuss the structure and function of the parts of the mouth.

Salivary Glands

12. Describe the location, cellular composition, and secretory output of the major and minor salivary glands.

Composition of Saliva

13. Discuss the chemical and enzymatic constituents of saliva and their actions on ingested food.

Salivation

14. Discuss the factors that control salivation and the reasons particular responses are required.

15. Discuss the appearance and consequences of myxovirus infection of salivary and similar glands.

Tongue

16. Examine the general construction of the tongue and purpose of the different types of muscle.

17. Point out the function of various papillae and glands of the tongue.

Teeth

18. Specify the properties of each strata of the tooth structure, along with the means of connection to the mandible and maxilla.

19. Describe tooth shapes and functions that accompany the two dentitions.

Mechanical and Chemical Digestion in the Mouth

20. Discuss mastication as a means of reducing food to minute particles that are collected in a bolus for deglutination.

21. Discuss the nature of degradation products from the action of salivary enzymes on specific food substrates.

PHARYNX

23. Describe the location and function of the pharynx.

23. Discuss the events of the three stages of swallowing.

ESOPHAGUS

25. Describe the location of the esophagus.

Histology of the Esophagus

26. Describe the tissue composition for changes in the epithelium, submucosa, muscularis, and serosa from the top of the esophagus to the merger with the stomach.

Physiology of the Esophagus

27. Describe the interactions between the medulla and esophageal muscularis that facilitate the peristalsis of a food bolus from the upper to the lower sphincter.

27. Discuss the causes and consequences of gastroesophageal reflux disease.

STOMACH

29. Describe the location and functions of the stomach.

Anatomy of the Stomach

30. Discuss the four areas of the stomach anatomy with their associated specializations in the muscularis, surface topography, and terminology.

30. Define pylorospasm and pyloric stenosis and discuss their consequences.

Histology of the Stomach

32. Explain the cellular nature of the stomach lining, in addition to the morphology of gastric pits and digestive purpose of the several types of secretory cells.

Mechanical and Chemical Digestion in the Stomach

33. Describe the progressive mixing movements, which are produced by the stomach muscularis, that prepare and eject chyme through the pyloric sphincter.

33. Explain the function of the acid and enzymes of the stomach in protection against pathogens and in the initial breakdown of proteins and lipids during digestion.

34. Name some substances that are absorbed into the blood from the stomach.

Regulation of Gastric Secretion and Motility

36. Discuss the neural and hormonal direction of gastric secretion and contraction that occur in the three phases of digestion.

Cephalic Phase

37. Discuss the progression of CNS areas that are stimulated by the perception of food and result in production of particular gastric secretions and motility.

Gastric Phase

38. Illustrate the operation of each neural and hormonal component in the negative feedback regulation of gastric secretion and contraction initiated by stretch and chemoreceptors.

Intestinal Phase

39. Discuss the reasons for the responses and actions of each enteric hormone and the enterogastric reflex in control of acid and enzyme secretion and mixing movements of the stomach.

Regulation of Gastric Emptying

40. Discuss the rationale and steps in the control of chyme pH and chemical composition before release of chyme from the stomach into the duodenum.

40. Discuss the process of vomiting and the stimuli that cause this process.

PANCREAS

Anatomy of the Pancreas

42. Identify the accessory organs with which the pancreas works to assist the small intestines in digestion of food.

Histology of the Pancreas

43. Describe the form and secretions of the exocrine and endocrine cell clusters within the pancreas.

Pancreatic Juice

43. Discuss the chemical character and range of enzyme functions possessed by pancreatic juice involved in the processing of food molecules.

44. Discuss pancreatitis and some of its causes.

Regulation of Pancreatic Secretion

45. Describe the neural and hormonal controls over pancreatic secretion.

LIVER AND GALLBLADDER

47. Anatomically locate the liver and disclose its massive proportions relative to other organs.

47. Discuss the position, appearance, and job of the gallbladder with respect to the liver and duodenum.

Anatomy of the Liver and Gallbladder

48. Describe the morphology of the liver’s lobes, ligaments, vessels, and ducts.

Histology of the Liver and Gallbladder

49. Describe the cellular, vascular, and duct arrangements and duties of the liver lobule.

50. Describe how the epithelial and smooth muscle structure of the gallbladder allows it to store and secrete bile.

Blood Supply of the Liver

51. Describe the network of arteries and portal veins that contribute to the blood flow into the sinusoids and then merge into the central and hepatic veins.

52. Discuss the purpose of the odd convergence of arteries and veins in the hepatic lobule.

Bile

53. Describe the source and characteristics of bile fluid and general function of bile constituents in absorption of fat and excretion of certain materials from the body.

Regulation of Bile Secretion

54. Discuss the neural and hormonal factors that regulate bile secretion.

Functions of the Liver

55. Discuss the nine essential functions of the liver in metabolism and homeostasis.

56. Discuss the formation of gallstones and their clinical significance.

SUMMARY: DIGESTIVE HORMONES

58. Discuss the sources and functions of hormones that coordinate the action of the digestive organs in the processing of food.

SMALL INTESTINE

59. Review the extent and features of the small intestines that enable them to serve as the primary site of digestion and absorption of food materials.

Anatomy of the Small Intestine

60. Distinguish the connections, locations, length, and specialized gross structures of the three segments of the small intestine.

Histology of the Small Intestine

61. Illustrate the duties, arrangement, and distinct membrane forms of the epithelial cells, and then discuss their relation to the underlying tissue in the process of degradation and absorption of food substances.

61. Discuss the specialization of the MALT that exist in the tissues of the small intestines.

Intestinal Juice and Brush Border Enzymes

63. Discuss the chemical secretions and membrane-bound enzymes of the small intestinal epithelium.

Mechanical Digestion in the Small Intestine

64. Discuss the mechanical actions of smooth muscle in production of segmentation and peristaltic movements that mix and propel the digestate within the small intestine.

Chemical Digestion in the Small Intestine

Digestion of Carbohydrates

65. Discuss the chemical digestion of carbohydrates in the small intestine.

65. Describe what happen when the intestinal cells no long produce lactase.

Digestion of Proteins

67. Discuss the chemical digestion of proteins in the small intestine.

Digestion of Lipids

68. Discuss the chemical digestion of lipids in the small intestine.

Digestion of Nucleic Acids

69. Discuss the chemical digestion of nucleic acids in the small intestine.

Regulation of Intestinal Secretion and Motility

70. Discuss the conditions that stimulate vasoactive intestinal polypeptide output, local and autonomic reflexes to control intestinal secretion and different types of motility that facilitate breakdown and absorption of food molecules.

Physiology of Absorption in the Small Intestine

71. Describe the end products of chemical digestion of carbohydrates, proteins, and lipids.

Absorption of Monosaccharides

72. Discuss the transport mechanisms that are responsible for movement of different monosaccharides from the intestinal lumen into the epithelial cell and then into capillaries.

Absorption of Amino Acids, Dipeptides, and Tripeptides

73. Explain the ways the transport of different amino acids is related to active processes.

Absorption of Lipids

75. Discuss the sequence of processes that perform absorption of fatty materials, from the interacations with lipase enzymes and bile to form micelles to the construction of chylomicrons and transport in the lacteal capillaries.

Absorption of Electrolytes

76. Discuss the regulated active and passive means by which ions are transported and cotransported into the blood from the intestines.

Absorption of Vitamins

77. Explain how vitamins move into the blood via methods that are related to their water or lipid soluble nature.

Absorption of Water

78. Describe the locations and volumes of water entry into the GI tract, and then the reabsorption by osmosis established by nutrient and electrolyte movements.

LARGE INTESTINE

79. List the prominent functions of the large intestine.

Anatomy of the Large Intestine

80. Describe the changes in the gross anatomy of the large intestine from the ileocecal valve to the anal canal.

80. Discuss the symptoms and possible consequences of appendicitis.

Histology of the Large Intestine

82. Associate particular cell types with the absorptive and mucous secreting functions of the epithelial lining, and then tell how the smooth muscles of the colon form peculiar structures to support its duties.

Mechanical Digestion in the Large Intestine

83. Describe the mechanical movements that occur in the large intestine.

Chemical Digestion in the Large Intestine

84. Explain the role of bacteria in the final degradation of food substances, and the absorption of the last substrates and particular vitamins.

Absorption and Feces Formation in the Large Intestine

85. Discuss the processes involved in the absorption of the remaining water and electrolytes and the formation of feces.

Defecation Reflex

86. Establish the interactions between the stretch receptors of the rectum and reflexive responses of the internal and external anal sphincters that promote expulsion of feces at a consciously selected time.

86. Discuss the effect of dietary fiber on the working of the large intestine.

DEVELOPMENTAL ANATOMY OF THE DIGESTIVE SYSTEM

88. Describe the development of the digestive system.

AGING AND THE DIGESTIVE SYSTEM

89. Describe the effects of aging on the digestive system.

DISORDERS: HOMEOSTATIC IMBALANCES

90. Describe the clinical symptoms of the following disorders: dental caries, periodontal disease, peptic ulcer disease, diverticulitis, colorectal cancer, hepatitis, and anorexia nervosa.

MEDICAL TERMINOLOGY

91. Define medical terminology associated with the digestive system.

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