Transcript chapter_17_powerpoint_l-1

PowerPoint Lecture Outlines
to accompany
Hole’s Human
Anatomy and Physiology
Tenth Edition
Shier w Butler w Lewis
Chapter
17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Chapter 17
Digestive System
Functions of Digestive System
• ingestion
• mechanical digestion
• chemical digestion
• propulsion
• absorption
• defecation
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Major Organs
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Alimentary Canal
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Alimentary Canal Wall
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Structure of the Wall
• Serosa- made of visceral peritoneum,
moistens, protects and lubricates
• Muscular- smooth circular fibers-decreases
diameter-smooth longitudinal-shortens tube
• Sumucosa- nerves, blood vessels, loose c.t.,
transports absorbed nutrients and nourishes
• Mucosa- epithelial, some c.t., some muscle
secretes mucus, absorb, protect
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Movements of the Tube
• mixing movements
• peristalsis
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Innervation of the Tube
• submucosal plexus – controls secretions
• myenteric plexus – controls gastrointestinal motility
• parasympathetic impulses – increase activities of
digestive system
• sympathetic impulses – inhibit certain digestive actions
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Mouth
• ingestion
• mechanical
digestion
• prepares food for
chemical digestion
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Tongue
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Palate
• roof of oral cavity
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Primary Teeth
• 8 incisors
• 4 cuspids
• 8 molars
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Secondary Teeth
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Section of a Tooth
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Salivary Glands
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Secretions of Salivary Glands
• Parotid glands
• clear
• water, serous fluid
• rich in amylase
• Sublingual glands
• primarily mucus
• most viscous
• Submandibular glands
• primarily serous
fluid
• some mucus
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Chemical Digestion in Mouth
Saliva
• 1-1.5 L per day
• Mostly water as a solvent so food can be
tasted
• Mucin-causes food to stick together has
lysozyme to kill bacteria
• Amylase-breaks down starch
• Neutralizes mouth acids-6.8, cleans mouth
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Pharynx
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Pharynx
• Connects nasal and oral cavities with larynx
and esophagus, lined with mucous mem.,
muscles constrict
• Nasopharynx- above soft palate has
pharyngeal tonsils on walls, behind nose,
passageway for air
• Oropharynx- below soft palate above
epiglottis, palatine tonsils on walls, food/air
• Laryngopharynx- from epiglottis
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downward to the esophagus
Swallowing Mechanism
• soft palate and uvula raise-nasal air passage shut off
• hyoid bone and larynx elevate, epiglottis closes off trachea
• tongue pushes against soft palate
• longitudinal muscles of pharynx contract pulling pharynx up
• inferior constrictor muscles relax and esophagus opens
• peristaltic waves push food through pharynx to the
esophagus, to the cardiac sphincter of the stomach
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Swallowing Mechanism
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Esophagus
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Stomach
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Radiograph of Stomach
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Lining of Stomach
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Gastric Secretions
• pepsinogen
• from chief cells
• inactive form of pepsin
• pepsin
• from pepsinogen in presence of
HCl
• protein splitting enzyme
• hydrochloric acid
• from parietal cells
• needed to convert
pepsinogen to pepsin
• mucus
• from goblet cells and mucous
glands
• protective to stomach wall
• intrinsic factor
• from parietal cells
• required for vitamin B12
absorption
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Phases of Gastric Secretion
• Cephalic phase
• triggered by smell, taste, sight, or thought of food
• parasympathetic impulses trigger gastric juice secretion-gastrin
• Gastric phase
• triggered by presence of food in
stomach
• gastrin released
• gastric juice secreted
• Intestinal phase
• triggered by movement of food into small intestine
• intestinal cells release intestinal gastrin
• secretion of gastric juice
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Regulation of Gastric
Secretions
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Gastric Absorption
• some water
• certain salts
• certain lipid-soluble drugs
• alcohol
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Mixing and Emptying Actions
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Enterogastric Reflex
regulates the rate at which chyme leaves the stomach
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Pancreas
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Pancreatic Juice
• pancreatic amylase – splits glycogen into
disaccharides
• pancreatic lipase – breaks down triglycerides
• trypsin, chymotrypsin, and carboxypeptidase –
digest proteins
• nucleases – digest nucleic acids
• bicarbonate ions – make pancreatic juice alkaline
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Regulation of Pancreatic
Secretions
• acidic chyme
stimulates release of
secretin
• secretin stimulate
release of pancreatic
juice
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Liver
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Hepatic Lobule
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The Paths of Blood and Bile in
Hepatic Lobule
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Liver Functions
• produces glycogen from glucose
• breaks down glycogen into glucose
• converts noncarbohydrates to glucose
• oxidizes fatty acids
• synthesizes lipoproteins, phospholipids, and cholesterol
• converts carbohydrates and proteins into fats
• forms urea
• synthesizes plasma proteins
• converts some amino acids to other amino acids
• stores glycogen, vitamins A,D, B12, iron, and blood
• phagocytosis of worn out RBCs and foreign substances
• removes toxins from blood
• produces and secretes bile
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Composition of Bile
• water
• bile salts
• emulsification of fats
• absorption of fatty acids, cholesterol, and fat-soluble
vitamins
• bile pigments
• cholesterol
• electrolytes
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Gallbladder
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Regulation of Bile Release
• fatty chyme entering
duodenum stimulate
gallbladder to release
bile
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Three Parts of Small Intestine
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Mesentery
• suspends portions of the
small intestine from the
posterior abdominal wall
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Intestinal Villus
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Intestinal Epithelium
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Wall of Small Intestine
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Secretions of Small Intestine
• peptidase – breaks down peptides into amino acids
• sucrase, maltase, lactase – break down disaccharides into
monosaccharides
• lipase – breaks down fats into fatty acids and glycerol
• enterokinase – converts trypsinogen to trypsin
• somatostatin – hormone that inhibits acid secretion by stomach
• cholecystokinin – hormone that inhibits gastric glands,
stimulates pancreas to release enzymes in pancreatic juice,
stimulates gallbladder to release bile
• secretin – stimulates pancreas to release bicarbonate ions in
pancreatic juice
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Regulation of Small
Intestinal Secretions
• mucus secretion stimulated by presence of chyme in
small intestine
• distension of intestinal wall activates nerve plexuses
in wall of small intestine
• parasympathetics trigger release of intestinal
enzymes
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Absorption in the
Small Intestine
• monosaccharides and
amino acids
• through facilitated
diffusion and active
transport
• absorbed into blood
• electrolytes and water
• through diffusion,
osmosis, and active
transport
• absorbed into blood
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Absorption in the
Small Intestine
• fatty acids and glycerol
• several steps
• absorbed into
lymph and blood
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Movements of the
Small Intestine
• mixing movements
• peristalsis – pushing movements
• segmentation – ringlike contractions
• overdistended wall triggers peristaltic rush
resulting in diarrhea
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Large Intestine
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Large Intestinal Wall
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Functions of Large Intestine
• little or no digestive function
• absorbs water and electrolytes
• secretes mucus
• houses intestinal flora
• forms feces
• carries out defecation
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Movements of Large Intestine
• slower and less frequent than those of small intestine
• mixing movements
• peristalsis
• mass movements usually follow meals
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Feces
• water
• electrolytes
• mucus
• bacteria
• bile pigments altered by bacteria provide color
• smell produced by bacterial compounds
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Life-Span Changes
• teeth become sensitive
• gums recede
• teeth may loosen or fall out
• heartburn more frequent
• constipation more frequent
• nutrient absorption decreases
• accessory organs age but the effects are less
noticeable
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Clinical Application
Hepatitis
• inflammation of the liver
• most commonly caused by viral infection
• can be caused by reactions to drug, alcoholism or autoimmunity
Signs and Symptoms
• headache
• low fever
• fatigue
• vomiting
• rash
• foamy urine
• pale feces
• jaundice
• pain
Hepatitis A – not washing hands or
eating raw shellfish
Hepatitis B – chronic; serum
Hepatitis C – serum
Hepatitis D – very severe; only produces
symptoms if infected with B; serum
Hepatitis E, F, G – more rare
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