Chapter 14 The Digestive System and Body Metabolism

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Chapter 14The Digestive System and Body
Metabolism
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• Digestive System Body Metabolism

• Digestion
• Breakdown of ingested food
• Absorption of nutrients into blood
• Metabolism
• Production of cellular energy (ATP)
• Constructive and degradative activities

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• Organs of the Digestive System

• Two main groups
• Alimentary canal continuous hollow tube
• Accessory digestive organs

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• Organs of the Alimentary Canal

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Anus

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• Mouth (Oral Cavity) Anatomy

• Lips (labia) protect
• Cheeks form lateral walls
• Hard palate forms anterior roof
• Soft palate forms posterior roof
• Uvula fleshy projection of the soft palate

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• Mouth (Oral Cavity) Anatomy

• Vestibule space between lips teeth and gums
• Oral cavity area contained by teeth
• Tongue attached at hyoid and styloid processes
  of the skull, and by the lingual frenulum

• Tonsils Palatine Lingual

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• Processes of the Mouth

• Mastication (chewing) of food
• Mixing food with saliva
• Start swallowing using tongue
• Sense of taste

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• Layers of Alimentary Canal Organs

• Mucosa - Moist membrane
• Surface epithelium
• connective tissue (lamina propria)
• Small smooth muscle layer

• Submucosa - under mucosa
• connective tissue with blood vessels, nerve
  endings, and lymphatics

• Serosa - Outermost layer visceral peritoneum
• Layer of serous fluid-producing cells

• Muscularis externa smooth muscle
• Inner circular layer Outer longitudinal layer

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• Alimentary Canal Nerve Plexuses

• Autonomic nervous system
• Three networks of nerve fibers
• Submucosal nerve plexus
• Myenteric nerve plexus
• Subserous plexus

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• Pharynx Anatomy

• Nasopharynx not part of the digestive system
• Oropharynx posterior to oral cavity
• Laryngopharynx below the oropharynx and
  connected to the esophagus

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• Pharynx Function

• Passageway for air and food
• Food moved by peristalsis
• alternating contractions of muscle layers
• Longitudinal inner layer
• Circular outer layer

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• Esophagus

• From pharynx to stomach through diaphragm
• Moves food by peristalsis
• Food only

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• Stomach Anatomy

• Left side of abdomen
• Food enters at cardioesophageal sphincter

• Regions
• Cardiac region near the heart
• Fundus
• Body
• Phylorus funnel-shaped terminal end
• Food empties into the small intestine at the
  pyloric sphincter

• Rugae internal folds of the mucosa

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• Stomach Anatomy

• External regions
• Lesser curvature
• Greater curvature

• Layers of peritoneum attached to the stomach
• Lesser omentum attaches liver to lesser
  curvature
• Greater omentum attaches greater curvature to
  posterior body wall
• fat insulates, cushions, protects

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• Stomach Functions

• Storage tank for food
• Physical breakdown
• Chemical breakdown of protein begins
• Delivers chyme (processed food) to the small
  intestine

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• Specialized Mucosa of the Stomach

• Simple columnar epithelium
• Mucous neck cells produce a sticky alkaline
  mucus
• Gastric glands secrete gastric juice
• Chief cells produce protein-digesting enzymes
  (pepsinogens)
• Parietal cells produce hydrochloric acid
• Endocrine cells produce gastrin

• Gastric pits formed by folded mucosa
• Glands and specialized cells are in the gastric
  gland region

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• Small Intestine

• Major digestive organ
• Nutrient absorption
• From pyloric sphincter to ileocecal valve
• Suspended from abdominal wall by mesentery

• 3 parts
• Duodenum - curves around pancreas
• Jejunum
• Ileum

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• Chemical Digestion in the Small Intestine

• Source of enzymes that are mixed with chyme
• Intestinal cells
• Pancreas
• Bile enters from the gall bladder

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• Villi of Sm. Intestine

Microvilli of Sm. Intestine

• Fingerlike structures formed by mucosa
• Give intestine more surface area

• Small projections of plasma membrane
• Found on absorptive cells

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• Large Intestine

• Wider, but shorter,frames the abdomen

• Cecum saclike first part
• Appendix - Hangs from the cecum

• Colon
• Ascending
• Transverse
• Descending
• S-shaped sigmoidal
• Rectum
• Anus external body opening

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• Functions of the Large Intestine

• Absorbs of water
• Eliminates feces indigestible food
• No digestion
• Goblet cells produce mucus as lubricant

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• Modifications to the Muscularis Externa in the
  Large Intestine

• Smooth muscle is reduced to three bands (teniae
  coli)
• Muscle bands have some degree of tone
• Walls formed into pocketlike sacs called haustra