Transcript The Human Body in Health and Illness

Digestive System
Lesson Objectives
• List four functions of the digestive system.
• Describe the four layers of the digestive tract.
• Describe the structure and functions of the
organs of the digestive tract.
• Describe the structure and functions of the
accessory organs of the digestive tract.
Digestive System
Other names:
-Alimentary Canal
-Gastrointestinal (GI) Tract
Functions of the Digestive System
Ingest food
Digest it
–Mechanical
–Chemical
Absorb nutrients
Excrete waste
Overview of the Digestive System
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Rectum, anus
Accessory organs
--Salivary glands
--liver
--gallbladder--pancreas
Four Layers of the Digestive Tract
Mucosal layer (innermost)
hormones, enzymes, mucus
Submucosal layer
nerves, glands, blood vessels
Muscle layer
- Circular and longitudinal
 Mixing, mashing action
- Peristaltic action
 “wave-like” motion
- Enteral nervous system
Serosal layer (outermost)
- Peritoneal membranes
Peritoneal Membranes
• Anchor organs
• Behind the
digestive organs
–Mesentery and
mesocolon
• In front of
organs
–Greater or lesser
omentum
Peritoneal Membranes
Greater omentum- “Lacy
Apron”
Mesentery
Peristalsis
• Waves of muscle
contraction, relaxation
• Pushes food from
mouth toward anus
• Peristaltic movements
differ from organ to
organ
Oral Cavity = Mouth
• Teeth: Mastication
– 2 sets:
• Deciduous: 20 “Milk teeth”
• Permanent: 32
• Tongue: Swallowing
– Forms bolus (food ball)
• Salivary glands
- Parotid
- Submandibular (below
jaw)
- Sublingual (below tongue)
Buccal cavity= gums to cheeks/lips
The Tooth
Three parts:
1. Crown = above
gum(gingiva)
2. Neck= connects
crown to root
3. Root= embedded in
jaw (dentin), has
pulp(sensation)
Shape
Shape and location indicate function
Incisors = tear and grasp
Cuspids (Canines) = tear and grasp
Premolars (bicuspids) = grind
molar = grind
Tongue
Two Roles
1. Positioning of Food
a) Bolus (food ball)
2. Taste Sensation
a) Taste buds
(poison)
Parts:
Frenulum: anchor
Sublingual blood
supply
Eating and Swallowing
• Mouth
– Hard and soft palates
– Uvula (for swallowing)
• Pharynx (throat)
– Laryngopharynx
– Oropharynx
• Epiglottis: covers trachea
• Esophagus
- Esophageal sphincters
Pharyngoesophageal
Lower esophageal
Borborygmus?
•What is
Borborygmus???
Functions of the Stomach
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Regulates rate of gastric emptying
Secretes gastric juice, HCl
Secretes gastric hormones
Digests limited amount of food
Absorbs limited substances
Parts of the Stomach
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Fundus
Body
Rugae
Lesser curvature
Greater curvature
Pylorus
Pyloric sphincter
Muscles of the Stomach
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Longitudinal
Oblique
Circular
Mixing and
mashing chyme
• Peristalsis
Stomach Structure: Mucosa
• Mucous cells
• Parietal cells
- HCl
- Intrinsic factor
• Chief cells
- Digestive enzymes
• Chyme: pastelike mixture
Small Intestine: Parts and Functions
Parts (Dow Jones Industrials)
(DJ Illy)
- Duodenum
- Jejunum
- Ileum
Functions
-Digests
-Absorbs
-Secretes hormones
and digestive enzymes
Villi and Microvilli
• Folds increase area for
absorption
• Inside composed of
capillaries and lacteals
• Deliveres to hepatic
portal system and
lymphatics
Duodenum
• 10 inches
• Receives Chyme of
stomach
• Accessory organ
secretions enter here
• Where MOST
DIGESTION and
ABSORPTION OCCURS
The Rest
Jejunum (2nd Part)
• 8 Feet
Ileum (3rd Part)
• 12 feet
• Connects to Cecum of L.I.
– Ileocecal valve
• Contains Peyer’s patches
-Control bacterial
numbers of L.I.
Large Intestine
• 5 feet
• Cecum
– Vermiform appendix
• Colon
-Ascending
-Transverse
-Descending
-Sigmoid
• Rectum
• Anal Canal  Anus
Functions of the Large Intestine
• Absorption of water and electrolytes
-Constipation: absorb too much water
-Diarrhea: not absorbing enough water
• Synthesis of vitamins by intestinal bacteria
• Temporary storage of waste
• Elimination of waste (feces) and gas (flatus)
Landmarks of Large Intestine
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Hepatic flexure: curve near liver (right side)
Splenic flexure: curve near spleen (left side)
Anal canal has 2 sphincters
Internal sphincter
– (involuntary)
• External sphincter
– (voluntary), potty training
Clinical Conditions: Stomach
A. Gastric ulcer
B. Hiatal hernia
C. Nasogastric tube
D. Gastric resection
E. Pyloric stenosis
F. Vagolytic effects
Gastrostomy tube
Clinical Conditions: Large Intestine
A. Intestinal
obstruction
B. Colostomy
C. Hemorrhoids
D. Enema
Accessory Digestive Organs
• Liver
• Gallbladder
• Pancreas
Liver Functions
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Synthesis of bile salts and secretion of bile
Synthesis of plasma proteins
Storage of glucose, fat-soluble vitamins
Detoxification
– Main organ for drug detoxification
• Excretion of bilirubin, cholesterol, drugs
• Metabolism of carbohydrates, protein, fats
• Phagocytosis: Kupffer cells (hepatic
macrophages)
Hepatic Portal System
• Liver processes end
products of digestion
• Discharging blood
through hepatic veins
and into Inferior Vena
Cava
Biliary Tree
• Ducts connect liver,
gallbladder, pancreas to
duodenum
• Hepatic ducts
• Cystic duct
• Common bile duct
– Ampulla of Vater
– Sphincter of Oddi
Gallbladder
• Pear-shaped sac
-underside of the liver
-concentrates and stores bile
• Attached to common bile duct by cystic duct
• Fat in the duodenum stimulates release of the
hormone cholecystokinin (CCK)
-CCK causes gallbladder to contract, eject
bile into common bile duct and
duodenum
Bile
• Formed from blood
in the liver lobules
• Assists in digestion of
fat
• Stored in gallbladder
• Composition
-Water
-Cholesterol
-Bile pigments
-Salts
Clinical Conditions
• Celiac Disease
– Unable to absorb certain
nutrients
• Gallstones
• Bleeding
– Loss of clotting factors
(liver failure)
• Esophageal varices
– Bleeding into esophagus
• Acute pancreatitis
Lesson 23-2 Objectives
• Explain the physiology of digestion and
absorption.
• Describe the effects of amylases, proteases,
and lipases.
• Describe the role of bile in the digestion of
fats.
• Describe five categories of nutrients.
Nutrition Basics
• Mechanical Digestion: change in
size
• Chemical Digestion: change in
chemical composition
• Food
-Carbohydrates
-Proteins
-Fats
-Vitamins and Minerals
• Specific Enzymes for each
type
– Ending of –ase indicates
enzymes
Fats: Digestion and Absorption
• Fats are insoluble in water.
• Emulsification
-Bile splits big fat globules into
small ones.
-Bile salts make fat watersoluble.
• Digestion
-Accomplished by lipases
-End products: Fatty acids and
glycerol, absorbed by lacteals
Carbohydrates: Digestion and Absorption
• Monosaccharides
-Simple sugars, end products of
digestion absorbed by villi
• Disaccharides
-Digested by disaccharidases to
monosaccharides
• Polysaccharides
-Digested by amylases to
disaccharides
Proteins: Digestion and Absorption
• Gastric HCl unravels strands of
protein
• Proteases digest protein into amino
acids, which are absorbed into villi
• Common proteases
-Pepsin, stomach
-Trypsin, pancreas
-Chymotrypsin, pancreas
-Enterokinase, duodenum
Digestion and Absorption: Summary
• Trace the flow of
food from the mouth
to the anus.
• Point out entrance of
each accessory organ
into the digestive
tract.
Nutrition: Concepts to Know
• Nutrition: Study of the relationship of food to
body function
• Five categories of nutrients
– Carbohydrates
– Proteins
– Lipids
– Vitamins
– Minerals
Nutrition Concepts: Carbohydrates
Simple Sugars
Complex Carbohydrates
• Monosaccharides
• Disaccharides
• Polysaccharides
• Consist primarily of
starch and fiber
• Most carbohydrate
consumption should be
in this form.
Nutrition Concepts: Proteins
• Essential amino acid: Not synthesized by the
body; must be consumed
• Nonessential amino acid: Synthesized in the
body; not essential to consume
• Complete protein: Contains all the essential
amino acids
• Incomplete protein: Does not contain all
essential amino acids
Nutrition Concepts: Fats
• Saturated fatty acid: Solid at room temperature
• Unsaturated fatty acid: Oil; liquid at room
temperature
• Essential fatty acid: Not synthesized by the body
and must be consumed; linoleic acid is an
important component of cell membranes
Nutrition Concepts: Vitamins
• Small organic molecules that help regulate cell
metabolism
• Fat-soluble vitamins
– Vitamins A, D, E, and K
– Can be stored in the body
• Water-soluble vitamins
– Vitamins B and C
– Most are not stored by the body
Nutrition Concepts: Minerals
• Inorganic substances needed for normal body
function
• Sodium, chloride
• Potassium
• Calcium, phosphorus, magnesium
• Iron
• Iodine
• Trace elements
Appetite Control
• Hypothalamus
– Feeding center
– Satiety center
• Theories of satiety
– Glucostat hypothesis
– Lipostat hypothesis