Download Digestive System Notes

Digestive System
Other names: Alimentary Canal (entire tube) or Gastrointestinal (GI) Tract (Usually stomach and intestine)
Functions of the Digestive System
 Ingestion: Ingest food
 Digestion: Digest it
o Mechanical
o Chemical
 Motility: movement
o (Peristalsis and segmentation)
 Secretion: Release digestive juices
 Absorption: Absorb nutrients
 Elimination: Excrete waste
Organs of the Digestive System
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Rectum, anus
 Accessory organs
o Salivary glands --Liver--Gallbladder --Pancreas-Teeth
Four Layers of the Digestive Tract
1. Mucosal layer (innermost) hormones, enzymes, mucus
2. Submucosal layer: nerves, glands, blood vessels
3. Muscle layer
a. Circular and longitudinal: Mixing, mashing action
b. Peristaltic action: “wave-like” motion
c. Enteric nervous system
4. Serosal layer (outermost): peritoneal membranes
Peristalsis: waves of muscle contraction, relaxation
 Pushes food from mouth toward anus
o differ from organ to organ
Peritoneal Membranes
 Anchor organs
o Behind the digestive organs: Mesentery and
mesocolon
o In front of organs: Greater or lesser omentum
Oral Cavity = Mouth
 Majority of mechanical digestion
 Organs to do this:
o Teeth: Mastication: 2 sets
 Deciduous: 20 “Milk teeth”
 Permanent: 32
o Tongue: used for Deglutition (swallowing)
 Forms bolus (food ball)
o Salivary glands (3 types)
 Parotid
 Submandibular (below jaw)
 Sublingual (below tongue)
o Buccal cavity= gums to cheeks/lips
The Tooth: Shape and location indicate function
Three parts:
1. Crown = above gum(gingiva)
2. Neck= connects crown to root
3. Root= embedded in jaw (dentin), has
pulp(sensation)
Tongue: 2 roles
1. Positioning of Food (Bolus (food ball))
2. Taste Sensation: Taste buds (poison)
Parts of tongue:
 Frenulum: anchor
 Sublingual blood supply
Eating and Swallowing
 Mouth
o Hard and soft palates
o Uvula (for swallowing)
 Pharynx (throat)
o Laryngopharynx
o Oropharynx
 Epiglottis: covers trachea
 Esophagus
o Esophageal sphincters
 Pharyngoesophageal
 Lower esophageal
Functions of the Stomach
o Regulates rate of gastric emptying
o Secretes gastric juice, HCl
o Secretes gastric hormones
o
o
Digests limited amount of food
Absorbs limited substances
Parts of the Stomach
o Fundus
o Body
o Rugae
o Lesser curvature
o Greater curvature
o Pylorus
o Pyloric sphincter
Muscles of the Stomach
o Longitudinal, Oblique, and Circular
o Meant for mixing and mashing chime
o Peristalsis
Stomach Structure: Mucosa
o Mucous cells
o Parietal cells
o HCl
o Intrinsic factor
o Chief cells
- Digestive enzymes
Use all these to make Chyme: paste-like mixture
Small Intestine: Parts and Function
o Parts (Dow Jones Industrials or DJ Illy)
o Duodenum
 10 inches
 Receives Chyme of stomach
 Accessory organ secretions enter here
 Where MOST DIGESTION and ABSORPTION OCCURS
o Jejunum: 2nd part, 8 feet
o Ileum: 3rd part 12 feet, Connects to Cecum of Large intestine
 Ileocecal valve: junction where S.I. meets L.I.
 Contains Peyer’s patches
 Control bacterial numbers of L.I.
o Functions
-Digests
-Absorbs
-Secretes hormones and digestive enzymes
Villi and Microvilli of Small intestine
o These are the folds that increase area for absorption
o Inside composed of capillaries and lacteals
o Delivers to hepatic portal system and lymphatic
Large Intestine: 5 feet
o Parts
o Cecum
 Vermiform(worm-like) appendix
o Colons
 Ascending
 Transverse
 Descending
 Sigmoid
o Rectum
o Anal Canal Anus
Functions of the Large Intestine
o Absorption of water and electrolytes
o Constipation: absorb too much water
o Diarrhea: not absorbing enough water
o Synthesis of vitamins by intestinal bacteria
o Temporary storage of waste
o Elimination of waste (feces) and gas
(flatus)
Landmarks of Large Intestine
o Hepatic flexure: curve near liver (right
side)
o Splenic flexure: curve near spleen (left
side)
o Anal canal has 2 sphincters
o Internal sphincter (involuntary)
o External sphincter (voluntary),
potty training
Clinical Conditions: Stomach
Gastric ulcer
Hiatal hernia
Nasogastric tube
Gastric resection
Pyloric stenosis
Vagolytic effects
Gastrostomy tube
Clinical Conditions: Large Intestine
Intestinal obstruction
Colostomy
Hemorrhoids
Enema
Accessory Digestive Organs
Liver
Gallbladder
Pancreas
Liver Functions
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
Monosaccharides
Disaccharides
Complex Carbohydrates
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