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Chapter 16 – digestive system
Major components: mouth, esophagus, stomach, intestines, liver, gallbladder, and pancreas
Major functions: mechanical and chemical breakdown of food, absorption of nutrients and elimination of wastes
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Histology of the digestive system
Four tissue layers (tunics):1. Mucosa – innermost tunic – mucus epithelium, lamina propria, muscularis mucosa2. Submucosa – thick layer of loose connective tissue3. Muscularis – inner layer of circular smooth muscle and outer layer of longitudial smooth muscle4. Serosa or adventitia – connective tissue layer
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Structures:
Oral cavity: mouth – bounded by lips and cheeks and contains teeth and tongue
Muscles – (lips) – orbicularis oris, buccinator, tongue, frenulum - (function – mastication)
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teeth
32 teeth in normal adult mouthLocated in mandible and maxillaIncisors, canines, premolars, molarsSee diagram page 452Permanent vs. deciduous teethStructure: crown, neck, root, pulp cavity, pulp, dentin, enamel, cementum, alveoli, gingiva, periodontal ligaments, periodontal membrane
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Palate and tonsils
Palate – 2 parts:
1. Hard palate
2. Soft palate
Uvula
Tonsils – lateral, posterior walls of the oral cavity
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Salivary glands
See diagram on pg. 453
Three pairs –
1. parotid
2.Submandibular
3.sublingual
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pharynx
Nasopharynx
Oropharynx
laryngopharynx
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esophagus
Muscular tube – extends from pharynx to stomach
About 10 inches (25 cm)
Passes through diaphragm
Upper and lower esophageal sphincters
Lined with mucous glands
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Stomach
Cardiac opening
Cardiac region
Fundus
Body
Greater curvature
Lesser curvature
Pyloric opening (sphincter)
Pyloric region
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Stomach, continued
Gastric pits
Gastric glands
Mucous cells
Endocrine cells
Pepsinogen/pepsin
rugae
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Small intestine
About 6 meters long (almost 20 ft)
3 sections: duodenum, jejunum, ileum
Duodenum – about 12 inches, bile duct and pancreatic duct empty into it
Duodenum has : circular folds, villi and microvilli to increase surface area
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Small intestine, cont’d
Jejunum and ileum are similar in structure to duodenum, but diameter and numbers of villi, microvilli and circular folds decreases as you progress the length of the small intestine
Ileocecal junction, sphincter and valve are found at the junction between the ileum and the large intestine
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liver
Weighs about 3 pounds
Right upper quadrant of abdomen
2 blood sources
Ducts transport bile to gall bladder
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pancreas
Pancreatic islets
Insulin production
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Large intestine
Cecum
Colon
Rectum
Anal canal
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Colon
1.5 m long
Ascending
Transverse
Descending
Sigmoid
Crypts
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peritoneum
Serous membranes
Visceral peritoneum
Parietal peritoneum
Mesenteries
Lesser/greater omentum
Retroperitoneal organs
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Physiology of digestive system
Oral cavity, pharynx and esophagus
Saliva – salivary amylase
Mucin
Mastication
Deglutition
Voluntary phase
Bolus
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Swallowing, contd
Pharyngeal phase
Epitglottis
Esophageal phase
Peristaltic waves
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Stomach
Secretions – chyme
Mucus
Hydrochloric acid
Pepsiogen
Pepsin
Intrinsic factor
gastrin
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Regulation of stomach secretions
Cephalic phase
Gastric phase
Intestinal phase
Secretin
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Movement in the stomach
Mixing waves
Peristaltic waves
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Small intestine
Peptidases
Disaccharidases
Movement – segmental contractions, peristaltic contractions
absorption
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liver
Digestive, excretory,stores and processes nutrients, synthesizes molecules, detoxifies
Bile/bile salts
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pancreas
Trypsin
Pancreatic amylase
Lipases
Nucleases
insulin
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Large intestine
Feces
Defecation
Mass movements
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Digestion, absorption, transport
Carbohydrates – mono, di and poly saccharides
Lipids – triacylglycerol, saturated and unsaturated fats
Proteins – pepsin, trypsin, peptidases and amino acids
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Water and minerals
9 L of water enters digestive tract per day
1.5 of those in food and drink
7.5 L from digestive secretions