Transcript chapt17_lecture blank

Chapter 17
Digestive System
Functions of Digestive System
•
• mechanical digestion
• chemical digestion
•
• absorption
•
17-2
Major Organs
17-3
Alimentary Canal
17-4
Alimentary Canal Wall
17-5
Movements of the Tube
• mixing movements
•
17-6
Mouth
• ingestion
•
• prepares food for
chemical digestion
17-8
Palate
• roof of oral cavity
17-10
Primary Teeth
• 8 incisors
• 4 cuspids
• 8 molars
cross of tooth.mov
Teeth and Plague.mov
17-11
Salivary Glands
17-14
Swallowing Mechanism
17-18
Esophagus
17-19
Stomach
17-20
Lining of Stomach
Endoscopy of Stomach.mov
Stomach.mov
17-22
Gastric Secretions
• pepsinogen
• inactive form of pepsin
•
• protective to stomach wall
•
• from pepsinogen in presence of
HCl
• protein splitting enzyme
• intrinsic facto
• required for vitamin B12
absorption
•
• from parietal cells
• needed to convert
pepsinogen to pepsin
17-23
Phases of Gastric Secretion
• Cephalic phase
•
• parasympathetic impulses trigger gastric juice secretion
• Gastric phase
•
• gastrin released
• gastric juice secreted
• Intestinal phase
•
• intestinal cells release intestinal gastrin
• secretion of gastric juice
17-24
Gastric Absorption
• some water
• certain salts
• certain lipid-soluble drugs
• alcohol
17-26
Mixing and Emptying Actions
17-27
Pancreas
17-29
Pancreatic Juice
• pancreatic amylase –
• pancreatic lipase – breaks down triglycerides
• trypsin, chymotrypsin, and carboxypeptidase –
• nucleases –
• bicarbonate ions – make pancreatic juice alkaline
17-30
Liver
17-32
Liver Functions
•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
•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
17-35
Gallbladder
gall stones.mov
17-37
Three Parts of Small Intestine
17-39
Intestinal Villus
17-41
Intestinal Epithelium
17-42
Wall of Small Intestine
17-43
Secretions of Small Intestine
• peptidase –
• sucrase, maltase, lactase –
• lipase –
• 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
17-44
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
17-46
Movements of the
Small Intestine
• mixing movements
• peristalsis –
• segmentation – ringlike contractions
• overdistended wall triggers peristaltic rush
resulting in diarrhea
Small intestine.mov
17-48
Large Intestine
17-49
Large Intestinal Wall
17-50
Functions of Large Intestine
•
•
• secretes mucus
•forms feces
• carries out defecation
17-51
Movements of Large Intestine
• slower and less frequent than those of small intestine
• mixing movements
• peristalsis
• mass movements usually follow meals
17-52
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
17-54
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
17-55