Chapter 24, part 1 The Digestive System

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

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

SECTION 24-1 The Digestive System

The Digestive system includes: The muscular digestive tract Various accessory organs

Figure 24.1 The Components of the Digestive System

Functions of the digestive system Ingestion Mechanical processing Digestion Secretion Absorption Excretion

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

Figure 24.2 Mesenteries Figure 24.2a

Figure 24.2 Mesenteries Figure 24.2b

Figure 24.2 Mesenteries Figure 24.2c

Figure 24.2 Mesenteries Figure 24.2d

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

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

Figure 24.3 The Structure of the Digestive Tract

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

Figure 24.4 Peristalsis Figure 24.4

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

Figure 24.5 The Regulation of Digestive Activities