THE DIGESTIVE SYSTEM

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THE DIGESTIVE SYSTEM

• CHAPTER 25

http//www.youtube.com/watch?v9FEACJ-cXsY
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System Overview

• Digestive Organs
• Alimentary Canal mouth, esophagus, stomach,
  small intestine, large intestine, rectum

http//www.youtube.com/watch?v9FEACJ-cXsY
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• Accessory Organs salivary glands, teeth,
  pancreas, liver, gall bladder

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• Digestive Processes
• Ingestion taking in food
• Propulsion moving food along
• Deglutition breaking food into smaller pieces

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• Peristalsis involuntary smooth muscle wavelike
  contractions
• Mechanical digestion stomach churning
• Mastication - chewing

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• Chemical digestion begins in the mouth and
  continues through small intestine
• carbohydrates into simple sugars
• proteins into amino acids
• lipids into fatty acids and glycerol

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• Absorption through lining of small intestine
• Defecation eliminating undigestible solid
  material

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Anatomy

• Peritoneum
• visceral peritoneum membrane that covers
  outside of organs
• parietal peritoneum membrane that lines
  abdominopelvic cavity forms ligaments to suspend
  organs.

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Abdominal Serous Membranes
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• falciform ligament binds liver
• lesser omentum binds stomach

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• greater omentum binds small and some of large
  intestine
• Mesocolon binds large intestine

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• Mesentery - suspends small intestine

• peritoneal cavity abdominal cavity

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Histology

• 4 basic layers
• mucosa innermost layer, lines lumen secretes
  enzymes and hormones
• Submucosa contains nerve endings, blood
  vessels, lymphatic vessels (lacteals) absorption
  

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• muscularis smooth muscle layer motility
• serosa outermost layer secretes serous fluid
  to lubricate

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Alimentary Canal (GI Tract) Anatomy

• Mouth contains teeth, tongue and salivary
  glands. Mechanical digestion chemical digestion
  of starches begins here

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• goblet cells secrete mucus (protection)
• parietal cells secretes HCl and intrinsic
  factor (absorbs vitamin B12)

• Stomach
• Chyme consistency of toothpaste

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• chief cells secrete pepsinogen which is
  activated by HCl when stomach pH rises (from
  ingestion of proteins)

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• G cells secrete gastrin

• Rugae folds in stomach lining
• Modifications 3 muscle layers

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• Digestion mechanical chemical digestion of
  proteins begins here
• Absorption water and alcohol

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• Pathology ulcers (bacterial in origin), cancer,
  hiatal hernia, gastro-esophageal reflux disease

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• Small intestine
• Regions duodenum, jejunum, ileum
• Enzymes peptidases (proteins) dextrinases
  (sugars)

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• Modifications
• Villi increases surface area
• microvilli secretes enzymes
• plicae circularis keeps food rotating

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• Absorption sugars and amino acids fats absorbed
  through lacteals

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• Propulsion
• Absorption of water
• Pathology diarrhea, constipation, colon cancer,
  diverticulitis

• Colon (with appendix) E. coli colonies here help
  manufacture vitamin K

Progression from polyp to cancer
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• Liver Gall Bladder
• Responsible for producing bile, process
  nutrients, store glycogen, store fat soluble
  vitamins, detoxification.

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• Kupffer cells- phagocytic cells
• Hepatocytes- liver cells

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• Bile made in liver, stored in gall bladder
  emulsifies fats

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• Pathology gall stones, cirrhosis, hepatitis,
  liver cancer

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• Pancreas
• Proteases proteins
• lipases fats
• amylases - starches
• nucleases nucleic acids
• Insulin (hormone) sugar
• metabolism
• Pathology diabetes mellitis,
• pancreatitis

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Hormonal Control

• Gastrin secretion stimulated by proteins and
  caffeine stimulates secretion of HCl feedback
  mechanism
• Enterogastrone secreted by duodenum in response
  to high fat content of diet slows stomach
  activity

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• Secretin
• produced by duodenum in response to fatty and
  acidic chyme
• stimulates pancreas to secrete bicarbonate ions
  and increase bile output
• CCK
• produced by duodenum in response to fatty chyme
• stimulates pancreas to secrete digestive enzymes

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General Pathology
Periodontal disease

• dysentery
• food poisoning
• periodontal disease
• mumps
• hepatomas
• enteritis
• colitis
• ileitis
• Crohns Disease

mumps
hepatoma
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Any Questions?