2. 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
3. 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
5. 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
6. 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
7. 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
10. 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
12. 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
13. An Example of a SphincterAn Example of a Sphincter
MuscleMuscle
14. Secretions of DigestionSecretions of Digestion
• Five organs
• Salivary glands, stomach, pancreas, liver,
small intestine
• Secretions
• Water
• Enzymes
• Protein facilitator of chemical reactions
• Hydrolysis
15. Secretions of DigestionSecretions of Digestion
• Saliva
• Moisten food for easy passage
• Protective role
• Carbohydrate digestion
• Gastric juice
• Protein digestion
• Mucus
• pH units
17. 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
19. The Final StageThe Final Stage
• Undigested residues
• Exercise intestinal muscles
• Retention of water
• Colon
• Intestinal bacteria
• Recyclable materials
• Water and dissolved salts
20.
21. AbsorptionAbsorption
• Small intestine
• Majority of absorption
• Ten feet long
• Surface area
• Absorption techniques
• Simple diffusion
• Facilitated diffusion
• Active transport
22. 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
cell
FACILITATED
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
23. 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
cell
FACILITATED
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
24. Anatomy of the AbsorptiveAnatomy of the Absorptive
SystemSystem
• Villi
• Select and regulate nutrients absorbed
• Microvilli
• Enzymes and “pumps”
• Crypts
• Secretion of intestinal juices
• Goblet cells
• Mucus secretion
25.
26. A Closer Look at the IntestinalA 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
27. 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
28. 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
31. 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
32. Health and Regulation of the GIHealth 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
33. Gastrointestinal Hormones andGastrointestinal Hormones and
Nerve PathwaysNerve Pathways
• Homeostatic regulation
• Endocrine system
• Nervous system
• Feedback mechanisms
• Examples
• GI hormones
• Gastrin
• Secretin
• Cholecystokinin (CCK)
34. An Example of a NegativeAn Example of a Negative
Feedback LoopFeedback Loop
35. The Primary actions ofThe Primary actions of
Selected GI HormonesSelected GI Hormones
36. 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
38. ChokingChoking
• Food slips into trachea
• Cuts off breathing
• International sign for choking
• Heimlich maneuver
• Foods commonly associated with choking
• Prevention of choking
42. Diarrhea
• Diarrhea
• Symptom of medical conditions & treatments
• Irritable bowel syndrome (IBS)
• Colitis
• Treatment
43. Irritable Bowel Syndrome and
Colitis
• Irritable bowel syndrome
• Characterization
• Cause
• Unknown
• Triggers
• Colitis
• Inflammation of large intestine
44. Celiac Disease
• Autoimmune disease
• Inflammation of small intestine
• Gluten-containing foods
• Symptoms
• Treatment
• Rehydration
45. ConstipationConstipation
• Not a disease
• Symptoms of constipation
• Causes
• Lifestyle
• Side effect of medications
• Prevention
• Fiber and water
• Physical activity
Figure 3-2 The Colon The colon begins with the ascending colon rising upward toward the liver. It becomes the transverse colon as it turns and crosses the body toward the spleen. The descending colon turns downward and becomes the sigmoid colon, which extends to the rectum. Along the way, the colon mixes the intestinal contents, absorbs water and salts, and forms stools.
Figure 3.2: The Colon. The colon begins with the ascending colon rising upward toward the liver. It becomes the transverse colon as it turns and crosses the body toward the spleen. The descending colon turns downward and becomes the sigmoid colon, which extends to the rectum. Along the way, the colon mixes the intestinal contents, absorbs water and salts, and forms stools.
Figure 3-8 A bsorption of Nutrients Absorption of nutrients into intestinal cells typically occurs by simple diffusion, facilitated diffusion, or active transport. Occasionally, a large molecule is absorbed by endocytosis — a process in which the cell membrane engulfs the molecule, forming a sac that separates from the membrane and moves into the cell.
Figure 3.9: Absorption of Nutrients. Absorption of nutrients into intestinal cells typically occurs by simple diffusion, facilitated diffusion, or active transport. Occasionally, a large molecule is absorbed by endocytosis — a process in which the cell membrane engulfs the molecule, forming a sac that separates from the membrane and moves into the cell.
