chapter32012
TRANSCRIPT
Digestion, Digestion, Absorption, and Absorption, and
TransportTransport
Chapter 3Chapter 3
DigestionDigestion
• Breaking down foods into nutrients• Prepare for absorption
• Challenges of digestion• Tasks of the mouth• Diaphragm• Steady movement• Lubrication of food• Digestive enzyme functions• Excretion of waste
Anatomy of the Digestive TractAnatomy of the Digestive Tract
• Gastrointestinal (GI) tract• Flexible and muscular• Path
• Mouth → esophagus → stomach → small intestine → large intestine → rectum → anus
• Lumen• Continuous
The Gastrointestinal TractThe Gastrointestinal Tract
Anatomy of the Digestive TractAnatomy of the Digestive Tract
• Mouth• Process of digestion begins
• Mastication
• Four basic taste sensations• Savory
• Aroma, texture, and temperature
• Pharynx• Bolus
Anatomy of the Digestive TractAnatomy of the Digestive Tract
• Esophagus• Two sphincters
• Upper esophageal sphincter
• Lower esophageal sphincter
• Stomach• Movement of bolus• Chyme• Pyloric sphincter
Anatomy of the Digestive TractAnatomy of the Digestive Tract
• Small intestine• Common bile duct
• Pancreas and gall bladder
• Three segments
• Large intestine (colon)• Ileocecal valve • Withdrawal of water• Rectum and anus
Transverse colon
Ascending colon
Descending colon
Sigmoid colonAnus
Rectum
Appendix
Opening from small intestine to large intestine
End of small intestine
Stepped Art
Figure 3-2 p72
Transverse colon
Ascending colon
Descending colon
Sigmoid colonAnus
Rectum
Appendix
Opening from small intestine to large intestine
End of small intestine
Stepped Art
Fig. 3-2, p. 72
Muscular Action of DigestionMuscular Action of Digestion
• Peristalsis• Circular and longitudinal muscles working
together• Rate and intensity of contractions vary
• Factors that may interfere with peristalsis
• Stomach action• Circular, longitudinal, and diagonal muscles• Timing the release of chyme
Stomach MusclesStomach Muscles
Muscular Action of DigestionMuscular Action of Digestion
• Segmentation• Contraction of circular muscles in small
intestine• Mix chyme
• Promote contact with absorption cells
• Sphincter contractions• Periodically open and close• Control pace of GI tract contents
An Example of a Sphincter An Example of a Sphincter MuscleMuscle
Secretions of DigestionSecretions of Digestion
• Five organs• Salivary glands, stomach, pancreas, liver,
small intestine
• Secretions• Water • Enzymes
• Protein facilitator of chemical reactions
• Hydrolysis
Secretions of DigestionSecretions of Digestion
• Saliva• Moisten food for easy passage• Protective role• Carbohydrate digestion
• Gastric juice• Protein digestion• Mucus• pH units
The Salivary Glands
Secretions of DigestionSecretions of Digestion
• Pancreatic juice and intestinal enzymes• Released via ducts into duodenum• Enzymes act on all three energy nutrients• Sodium bicarbonate
• Bile• Liver• Gallbladder
Summary of Digestive Secretions & Their Major Actions
The Final StageThe Final Stage
• Undigested residues• Exercise intestinal muscles• Retention of water
• Colon• Intestinal bacteria• Recyclable materials
• Water and dissolved salts
AbsorptionAbsorption
• Small intestine• Majority of absorption• Ten feet long
• Surface area
• Absorption techniques• Simple diffusion
• Facilitated diffusion
• Active transport
Carrier loads nutrient on outside of cell . . .
Carrier loads nutrient on outside of cell . . .
Outside cell
Cell membrane
. . . and then releases it on inside of cell.
. . . and then releases it on inside of cell.Inside
cellFACILITATED
DIFFUSION
Some nutrients (such as the water-soluble vitamins) are absorbed by facilitated diffusion. They need a specific carrier to transport them from one side of the cell membrane to the other. (Alternatively, facilitated diffusion may occur when the carrier changes the cell membrane in such a way that the nutrients can pass through.)
ACTIVE TRANSPORT
Some nutrients (such as glucose and amino acids) must be absorbed actively. These nutrients move against a concentration gradient, which requires energy.
Stepped Art
Some nutrients (such as water and small lipids) are absorbed by simple diffusion. They cross into intestinal cells freely.
SIMPLE DIFFUSION
Figure 3-8 p77
Carrier loads nutrient on outside of cell . . .
Carrier loads nutrient on outside of cell . . .
Outside cell
Cell membrane
. . . and then releases it on inside of cell.
. . . and then releases it on inside of cell.Inside
cellFACILITATED
DIFFUSION
Some nutrients (such as the water-soluble vitamins) are absorbed by facilitated diffusion. They need a specific carrier to transport them from one side of the cell membrane to the other. (Alternatively, facilitated diffusion may occur when the carrier changes the cell membrane in such a way that the nutrients can pass through.)
ACTIVE TRANSPORT
Some nutrients (such as glucose and amino acids) must be absorbed actively. These nutrients move against a concentration gradient, which requires energy.
Stepped Art
Some nutrients (such as water and small lipids) are absorbed by simple diffusion. They cross into intestinal cells freely.
SIMPLE DIFFUSION
Fig. 3-9, p. 78
Anatomy of the Absorptive Anatomy of the Absorptive SystemSystem
• Villi• Select and regulate nutrients absorbed
• Microvilli• Enzymes and “pumps”
• Crypts• Secretion of intestinal juices
• Goblet cells• Mucus secretion
A Closer Look at the Intestinal A Closer Look at the Intestinal CellsCells
• Villi cells• Regulate nutrient absorption based on needs
• Microvilli• Enzymes and ‘pumps’
• Specialized cells • Food combining
• Enhanced use in the body
A Closer Look at the Intestinal Cells
• Transport pathways• Bloodstream
• Water-soluble nutrients and smaller products of fat digestion
• Liver
• Lymphatic system• Larger fats and fat-soluble vitamins
• Chylomicrons
• Bypass liver at first
The Vascular SystemThe Vascular System
• Closed system of vessels• Heart pump
• Blood• Delivers oxygen and nutrients• Removes carbon dioxide and wastes• Blood flow
• Special routing for digestive system
• Liver
The Vascular SystemThe Vascular System
The LiverThe Liver
The Lymphatic SystemThe Lymphatic System
• One-way route• No pump• Circulation between cells
• Entry into bloodstream• Subclavian vein
• Nutrients in lymphatic vessels• Bypass liver at first
Health and Regulation of the GI Health and Regulation of the GI TractTract
• Gastrointestinal bacteria – flora • Most are not harmful
• Benefits of gastrointestinal bacteria
• Factors influencing bacteria presence• Diet – probiotics
• Prebiotics • Others
• Digestion of fibers and complex proteins• Vitamin production
Gastrointestinal Hormones and Gastrointestinal Hormones and Nerve PathwaysNerve Pathways
• Homeostatic regulation• Endocrine system• Nervous system• Feedback mechanisms
• Examples
• GI hormones• Gastrin
• Secretin
• Cholecystokinin (CCK)
An Example of a Negative An Example of a Negative Feedback LoopFeedback Loop
The Primary actions of The Primary actions of Selected GI Hormones Selected GI Hormones
The System at Its BestThe System at Its Best
• Sensitive and responsive to environment• Immunity against intestinal diseases• Defense against foreign invaders
• Health of digestive system• Healthy supply of blood• Lifestyle factors• Types of foods eaten
• Balance, moderation, adequacy, and variety
Common Digestive Common Digestive ProblemsProblems
Highlight 3Highlight 3
ChokingChoking
• Food slips into trachea• Cuts off breathing
• International sign for choking• Heimlich maneuver
• Foods commonly associated with choking• Prevention of choking
Normal Swallowing and Normal Swallowing and ChokingChoking
First Aid for ChokingFirst Aid for Choking
VomitingVomiting
• Vomiting• Adaptive mechanism of the body• Medical treatment
• Dehydration
• Self induced
Diarrhea
• Diarrhea• Symptom of medical conditions & treatments
• Irritable bowel syndrome (IBS)
• Colitis
• Treatment
Irritable Bowel Syndrome and Colitis
• Irritable bowel syndrome• Characterization• Cause
• Unknown
• Triggers
• Colitis• Inflammation of large intestine
Celiac Disease
• Autoimmune disease• Inflammation of small intestine
• Gluten-containing foods• Symptoms• Treatment
• Rehydration
ConstipationConstipation
• Not a disease• Symptoms of constipation• Causes
• Lifestyle• Side effect of medications
• Prevention• Fiber and water• Physical activity
Constipation
• Hemorrhoids• Diverticulosis• Laxatives• Harmful practices
• Colonic irrigation
Belching and GasBelching and Gas
• Belching• Swallowed air• Prevention
• Intestinal gas• Consumption of certain foods
• Individually determined
Heartburn and Heartburn and ““Acid Acid IndigestionIndigestion””
• Gastroesophageal reflux (heartburn)• Causes• Prevention
• Indigestion• Causes• Antacids and acid controllers
• Damage to esophagus• Barrett’s esophagus
Gastroesophageal Reflux
UlcersUlcers
• Peptic ulcers• Gastric ulcers• Duodenal ulcers
• Causes• Bacterial infection• Anti-inflammatory drugs• Excessive gastric acid secretion
• Ulcer treatment regimen
Strategies to Prevent or Alleviate Common GI Problems