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Chapter 24, part 1 The Digestive System
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Learning Objectives Identify the organs of the digestive system and their major functions Outline the mechanisms that regulate digestion Describe the anatomy of the organs and accessory organs of the digestive system Discuss the functions of the major structures and regions of the digestive system and discuss the regulation of their activities
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Learning Objectives Explain the significance of the large intestine in the absorption of nutrients Describe the events involved in the digestion of organic and inorganic nutrients Summarize the effects of the aging process on the digestive system
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SECTION 24-1 The Digestive System
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The Digestive system includes:
The muscular digestive tract Various accessory organs
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Figure 24.1 The Components of the Digestive System
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Functions of the digestive system
Ingestion Mechanical processing Digestion Secretion Absorption Excretion
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The digestive system organs and the peritoneum
Mesenteries Sheets of serous membranes that support portions of the digestive tract Greater omentum lies anterior to abdominal viscera Provides padding, protection, insulation, and energy reserves Lesser omentum
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Figure Mesenteries Figure 24.2a
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Figure Mesenteries Figure 24.2b
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Figure Mesenteries Figure 24.2c
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Figure Mesenteries Figure 24.2d
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Histological organization of the digestive tract
Mucosa lines digestive tract (mucous epithelium) Moistened by glandular secretions Lamina propria and epithelium form mucosa Submucosa Layer of dense irregular connective tissue
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Histological organization of the digestive tract
Muscularis externa Smooth muscle arranged in circular and longitudinal layers adventitia Serosa Serous membrane covering most of the muscularis externa
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Figure 24.3 The Structure of the Digestive Tract
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Movement of digestive materials
Visceral smooth muscle shows rhythmic cycles of activity Pacemaker cells Peristalsis Waves that move a bolus Segmentation Churn and fragment a bolus
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Figure Peristalsis Figure 24.4
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Control of the digestive system
Movement of materials along the digestive tract is controlled by: Neural mechanisms Parasympathetic and local reflexes Hormonal mechanisms Enhance or inhibit smooth muscle contraction Local mechanisms Coordinate response to changes in pH or chemical stimuli
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Figure 24.5 The Regulation of Digestive Activities
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