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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.
3. 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
5. Discuss the characteristic structure and duties of the epithelial, lamina
propria, and muscularis layers of the mucosa.
Submucosa
6. Describe the structural, neural, and secretory features of the submucosal
layer.
Muscularis
7. Describe the muscle changes, layers, and control through the extent of the GI
tract.
Serosa
8. 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.
10. Describe the mesentery tissue and functions, and then the conspicuous folds
that support the abdominal digestive organs.
11. Discuss the causes, symptoms, and seriousness of peritonitis.
MOUTH
12. Discuss the structure and function of the parts of the mouth.
Salivary Glands
13. Describe the location, cellular composition, and secretory output of the major
and minor salivary glands.
Composition of Saliva
14. Discuss the chemical and enzymatic constituents of saliva and their actions on
ingested food.
Salivation
15. Discuss the factors that control salivation and the reasons particular responses
are required.
16. Discuss the appearance and consequences of myxovirus infection of salivary
and similar glands.
Tongue
17. Examine the general construction of the tongue and purpose of the different
types of muscle.
18. Point out the function of various papillae and glands of the tongue.
Teeth
19. Specify the properties of each strata of the tooth structure, along with the
means of connection to the mandible and maxilla.
20. Describe tooth shapes and functions that accompany the two dentitions.
Mechanical and Chemical Digestion in the Mouth
21. Discuss mastication as a means of reducing food to minute particles that are
collected in a bolus for deglutination.
22. 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.
24. 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.
28. 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.
31. 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.
34. 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.
35. 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.
41. 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
44. Discuss the chemical character and range of enzyme functions possessed by
pancreatic juice involved in the processing of food molecules.
45. Discuss pancreatitis and some of its causes.
Regulation of Pancreatic Secretion
46. 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.
48. Discuss the position, appearance, and job of the gallbladder with respect to the
liver and duodenum.
Anatomy of the Liver and Gallbladder
49. Describe the morphology of the liver’s lobes, ligaments, vessels, and ducts.
Histology of the Liver and Gallbladder
50. Describe the cellular, vascular, and duct arrangements and duties of the liver
lobule.
51. Describe how the epithelial and smooth muscle structure of the gallbladder
allows it to store and secrete bile.
Blood Supply of the Liver
52. 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.
53. Discuss the purpose of the odd convergence of arteries and veins in the
hepatic lobule.
Bile
54. 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
55. Discuss the neural and hormonal factors that regulate bile secretion.
Functions of the Liver
56. Discuss the nine essential functions of the liver in metabolism and
homeostasis.
57. 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.
62. 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.
66. 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.
81. 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.
87. 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.