Chapter 25 Anatomy of the Digestive System

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Chapter 25Anatomy of the Digestive System
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Overview of the Digestive System

• Role of the digestive system
• Prepares food for absorption and use by all the
  cells of the body
• Food material not absorbed becomes feces that is
  eliminated
• Digestion depends on both endocrine and exocrine
  secretions and the controlled movement of
  ingested food materials through the
  gastrointestinal (GI) tract

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Overview of the Digestive System

• Organization of the digestive system
• Organs of digestion (Figure 25-1, Table 25-1)
• Form the alimentary canal or gastrointestian (GI)
  tract
• Extends through the abdominopelvic cavity
• Ingested food material passing through the lumen
  of the GI tract is outside the internal
  environment of the body

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Overview of the Digestive System

• Organization of the digestive system
• Wall of the GI tract (Figure 25-2, Table 25-2)
• Layers
• Mucosa
• Mucous epithelium epithelial tissue
• Lamina propria connective tissue
• Muscularis mucosae muscle tissue
• Submucosa
• Connective tissue with glands, vessels, and
  nerves
• Muscularis
• Smooth muscle
• Myenteric plexus
• Serosa
• Connective tissue and peritoneum
• Visceral layer of peritoneum

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Mouth

• Structure of the oral cavity (Figure 25-3)
• Lips
• Covered externally by skin and internally by
  mucous membrane
• Junction between skin and mucous membrane is
  highly sensitive
• Philtrum and tubercle
• When lips are closed, line of contact is oral
  fissure
• Cheeks
• Lateral boundaries of oral cavity
• Continuous with lips and lined by mucous membrane
• Formed in large part by buccinator muscle covered
  by adipose tissue
• Contain mucus-secreting glands

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Mouth

• Structure of the oral cavity
• Hard and soft palates
• Hard palate consists of portions of two maxillae
  and two palatines
• Soft palate is made of muscle arranged in an arch
• Fauces and uvula
• Tongue
• Solid mass of skeletal muscle covered by a mucous
  membrane (Figure 25-4)
• Important for mastication and deglutition
• Root, tip, and body
• Papillae located on dorsal surface of tongue
• Lingual frenulum anchors tongue to floor of mouth

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Mouth

• Salivary glands
• Three pairs of compound tubuloalveolar glands
  (Figure 25-6) secrete approximately 1 liter of
  saliva each day
• Buccal glands contribute less than 5 of total
  salivary volume but provide for hygiene and
  comfort of oral tissues
• Parotid glands
• Largest of the paired salivary glands
• Produce watery saliva containing enzymes (no
  mucus)
• Submandibular glands
• Compound glands that contain enzyme and
  mucus-producing elements
• Sublingual glands
• Smallest of the salivary glands
• Produce a mucous type of saliva (no enzymes)

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Mouth

• Teeth
• Typical tooth (Figure 25-7)
• Crown
• Exposed portion of a tooth
• Covered by enamel
• Neck
• Narrow portion that joins the crown to the root
• Surrounded by the gingivae (gums)
• Root
• Fits into socket of alveolar process
• Suspended by fibrous periodontal membrane
• Dentin and Cementum
• Pulp cavity
• Located in dentin
• Contains connective tissue, blood and lymphatic
  vessels, and sensory nerves

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Mouth

• Types of teeth (Figure 25-8)
• Deciduous teeth
• 20 baby teeth, which appear early in life
• First teeth appear at about 6 months of age
• One each month after that
• Shed between the ages of 6 and 13 years
• Permanent teeth
• 32 teeth, which replace the deciduous teeth
• Central incisors
• Lateral incisors
• Canines
• Premolars (1st, 2nd)
• Molars (1st,2nd,3rd)