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Mouth to Stomach

Mouth to Stomach. p. 455-461 & 470-474. Parts of the Digestive System. Alimentary canal / GI tract Accessory organs. The Alimentary Canal. Vestibule Tongue Papillae Lingual frenulum Mastication. Functions: ingestion, mechanical & chemical digestion (salivary glands). The Oral Cavity.

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Mouth to Stomach

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  1. Mouth to Stomach p. 455-461 & 470-474

  2. Parts of the Digestive System • Alimentary canal / GI tract • Accessory organs

  3. The Alimentary Canal

  4. Vestibule Tongue Papillae Lingual frenulum Mastication Functions: ingestion, mechanical & chemical digestion (salivary glands) The Oral Cavity

  5. Teeth

  6. Pharynx & Esophagus • 3 regions of pharynx • Srat. squam. epi. • Functions: • No digestion or absorption • Swallowing • Peristalsis

  7. Stomach – Main Functions • Temporary food storage • Mechanical & chemical digestion • Limited absorption – alcohol, aspirin

  8. Cardiac sphincter Pyloric sphincter Greater & lesser curvatures Greater & lesser omenta Fat deposits Lymph nodes Stomach Anatomy

  9. Modifications of theStomach Wall • Mucosa = simple columnar w/ goblet cells • Gastric pits – lead into tubular gastric glands, which secrete gastric juice • Muscular layer has THREE layers of muscle • Rugae – folds of stomach wall allow its size to increase after a meal • Stretch stimulates muscle contractions

  10. Gastric Glands

  11. Gastric Juice • Gastric glands are lined with: • Chief cells – secrete pepsinogen (inactive form of the enzyme pepsin) • Parietal cells – secrete hydrochloric acid (HCl) • HCl converts pepsinogen into pepsin, an enzyme that begins protein digestion – animation • Enteroendocrine cells – secrete gastrin (a hormone) • Goblet cells – near opening of gastric glands

  12. Control of Gastric Juice, cont’d • Stimuli (sight, smell, taste) cause: • Gastric juice secretion, which leads to • Gastrin (hormone) secretion • Increases secretion of gastric juice • Is this a positive or negative feedback mechanism? • POSITIVE! • Chyme (partially digested food) entering duodenum inhibits gastric juice secretion

  13. Action of Gastrin

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