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THE DIGESTIVE SYSTEM. CHAPTER 25. http://www.youtube.com/watch?v=9FEACJ-cXsY. System Overview. Digestive Organs Alimentary Canal – mouth, esophagus, stomach, small intestine, large intestine, rectum. http://www.youtube.com/watch?v=9FEACJ-cXsY. - PowerPoint PPT Presentation
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THE DIGESTIVE SYSTEM
CHAPTER 25
http://www.youtube.com/watch?v=9FEACJ-cXsY
System Overview•Digestive Organs•Alimentary Canal – mouth, esophagus, stomach, small intestine, large intestine, rectum
http://www.youtube.com/watch?v=9FEACJ-cXsY
•Accessory Organs – salivary glands, teeth, pancreas, liver, gall bladder
•Digestive Processes•Ingestion – taking in food •Propulsion – moving food along
•Deglutition – breaking food into smaller pieces
•Peristalsis – involuntary smooth muscle wavelike contractions
•Mechanical digestion – stomach churning
• Mastication - chewing
•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
•Absorption – through lining of small intestine
•Defecation – eliminating undigestible solid material
Anatomy
•Peritoneum•visceral peritoneum – membrane that covers outside of organs
•parietal peritoneum – membrane that lines abdominopelvic cavity; forms ligaments to suspend organs.
Abdominal Serous Membranes
•falciform ligament – binds liver
•lesser omentum – binds stomach
•greater omentum – binds small and some of large intestine
•Mesocolon – binds large intestine
•Mesentery - suspends small intestine
•peritoneal cavity– abdominal cavity
Histology
•4 basic layers•mucosa – innermost layer, lines lumen; secretes enzymes and hormones
•Submucosa – contains nerve endings, blood vessels, lymphatic vessels (lacteals); absorption
•muscularis – smooth muscle layer; motility
•serosa – outermost layer; secretes serous fluid to lubricate
•
Alimentary Canal (GI Tract) Anatomy
•Mouth – contains teeth, tongue and salivary glands. Mechanical digestion; chemical digestion of starches begins here
•Stomach – •Chyme – consistency of toothpaste
•goblet cells – secrete mucus (protection)
•parietal cells – secretes HCl and intrinsic factor (absorbs vitamin B12)
•chief cells – secrete pepsinogen which is activated by HCl when stomach pH rises (from ingestion of proteins)
•G cells – secrete gastrin
•Rugae – folds in stomach lining
•Modifications – 3 muscle layers
•Digestion – mechanical; chemical digestion of proteins begins here
•Absorption – water and alcohol
•Pathology – ulcers (bacterial in origin), cancer, hiatal hernia, gastro-esophageal reflux disease
•Small intestine – •Regions: duodenum, jejunum, ileum
•Enzymes: peptidases (proteins) dextrinases (sugars)
•Modifications•Villi – increases surface area •microvilli – secretes enzymes•plicae circularis – keeps food “rotating”
•Absorption: sugars and amino acids; fats absorbed through “lacteals”
• Colon (with appendix)– E. coli colonies here help manufacture vitamin K
•Propulsion•Absorption of
water•Pathology:
diarrhea, constipation, colon cancer, diverticulitis
Progression from polyp to cancer
•Liver & Gall Bladder •Responsible for producing bile, process nutrients, store glycogen, store fat soluble vitamins, detoxification.
•Kupffer cells- phagocytic cells
•Hepatocytes- liver cells
•Bile – made in liver, stored in gall bladder; emulsifies fats
•Pathology – gall stones, cirrhosis, hepatitis, liver cancer
•Pancreas • Proteases – proteins• lipases – fats• amylases - starches • nucleases – nucleic acids• Insulin (hormone)– sugar metabolism• Pathology – diabetes mellitis, pancreatitis
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
• 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
General Pathology•dysentery• food poisoning•periodontal disease•mumps•hepatomas•enteritis•colitis• ileitis•Crohn’s Disease
Periodontal disease
mumps
hepatoma
Any Questions?