Download The Gastrointestinal Tract

07-Apr-11
Digestion, Absorption and Transport
The Gastrointestinal Tract
Anatomy of the GI tract:
– mouth
– esophagus
– stomach
t
h
– small intestine
– large intestine
– rectum
– anus
Components
of
gastrointestinal
tract
The Gastrointestinal Tract
 Functions:
 Ingestion
 Transport
p
 Secretion
 Digestion
 Absorption
 Elimination
1
07-Apr-11
Assisting Organs
Salivary glands - saliva
– Moisten food
– Supply enzymes
Liver
– Produces bile
Gallbladder
– Stores and secretes
bile
Pancreas
– Secretes bicarbonate
– Secretes enzymes
From M to A: Digestion and Absorption
Mouth
 Tongue (Mixing)
 Teeth (Mastication)
Digestion
Physical movement
– Peristalsis
– Segmentation
Chemical breakdown
– Enzymes hydrolysis
From M to A: Digestion and Absorption
Mouth
Enzymes
Salivary amylase acts on starch
Lingual lipase acts on fat
Saliva
Moistens food for enzymes
activity and easier swallowing
Esophagus
– Transports food to stomach - bolus
– Esophageal sphincter (upper & lower)
2
07-Apr-11
From M to A: Digestion and Absorption
Epiglottis
Esophageal sphincter
From M to A: Digestion and Absorption
From M to A: Digestion and Absorption
Stomach
Stomach
Mechanical
function
– “Chewing”
Esophegeal
– Mixing
Hydrochloric acid
 Prepares protein for
digestion
 Activates enzymes
 “Disinfection”
Sphincter
Pepsin
 Begins protein
Pyloric sphincter
digestion
Gastric lipase
 Some lipids digestion
Gastrin (hormone)
 Stimulates gastric
secretion and
movement
Intrinsic factor
 Needed for absorption
of vitamin B12
3
07-Apr-11
The Small Intestinal Villi
From M to A: Digestion and Absorption
Small intestine:
Pyloric
 Duodenum
Sphincter
(25 – 30 cm)
 Jejunum (120 cm)
 Ileum (150 cm)
Assisting Organs:
 Liver & gallbladder
 Pancreas
The Small Intestinal Villi and Microvilli
Folds
From M to A: Digestion and Absorption
Pancreatic juices
 Bicarbonate
 Enzymes:
– Trypsin and chymotrypsin Proteins
– Amylases - Carbohydrates
– Lipases - Lipids
4
07-Apr-11
From M to A: Digestion and Absorption
pH of
Digestive
Tract
Secretions
How nutrients are transported?
Absorptive mechanisms
Facilitated diffusion
Passive diffusion
Active transport
Small intestine - Absorption
 Folds, villi, and microvilli
makes large absorptive
surface
 Most nutrients absorbed
 Fat
F
Fatt-soluble
l bl nutrients
t i t go
into lymph
 Other nutrients go into
blood
From M to A: Digestion and Absorption
Large Intestine - Colon
5
07-Apr-11
From M to A: Digestion and Absorption
Large intestine
 Nutrient digestion already completed
 Fermentation of undigested residues by
bacteria:
 Production of vitamins K, B12, thiamin,
riboflavin,
ib fl i biotin,
bi ti other
th B’s
B’
 Gases
 Short chain fatty acids
 Antibiotics – protectant
 Lactic acid to control pH
From M to A: Digestion and Absorption
Large intestine
Absorption
 Water
 Sodium, potassium, chloride
 Vitamin K and B group (produced by
bacteria)
 Bile
Waste Elimination
Circulatory Systems
Vascular system
– Heart
– Arteries
A i
– Capillaries
– Veins
6
07-Apr-11
Circulation of Nutrients
Excretion and elimination
Lungs
Excretes water and carbon dioxide
Kidneys filter blood
Excretes waste
Maintains water and ion balance
Summary of digestion and absorption
7
07-Apr-11
Circulatory Systems
The
Liver
Vascular system
– Portal vein
– Hepatic vein
Circulatory Systems
Lymphatic system
– Lymph
– Thoracic duct
Subclavian vein
8
07-Apr-11
Catabolic Enzymes Action
9
07-Apr-11
Waste Products Must Be Eliminated from the Body
Substances such as fiber that are not absorbed from the
intestine are eliminated from the gastrointestinal tract in the
feces
The waste products of metabolism are eliminated by the lungs,
the skin, and the kidneys
At the lungs, red blood cells release the carbon dioxide, which
is
i then
th exhaled
h l d into
i t the
th environment
i
t
A significant amount of water is also lost from the lungs, by
evaporation
Some water, minerals, and byproducts breakdown are lost
through the skin perspiration or sweat. But the kidney is the
primary site for the excretion of water and the nitrogen
nitrogen-containing byproducts of protein breakdown
The amounts of water and other substances excreted in the
urine are regulated so that homeostasis is maintained
Digestion of a Sandwich
Digestion of a Sandwich
10
07-Apr-11
Absorption – Modes of Transportation
The Gastrointestinal Tract
Complimentary organs
 Salivary glands
 Liver and gallbladder
 Pancreas
Digestive Tract - Functions
Physical Movement:
 Peristalsis
 Segmentation
Chemical Breakdown:
 Enzymes
 Hydrolysis
 Other secretions
11
07-Apr-11
Secretions of Digestion
Digestive Tract - Functions
Stomach
 Chyme
 Pyloric sphincter
Saliva
– Salivary glands
Water, salts,
mucus,
enzymes
Muscular Action of Digestive Tract
Stomach
Muscles
Esophegeal
Sphincter
Stomach mechanical action
Pyrolic
Sphincter
12
07-Apr-11
Digestive Tract - Functions
Stomach
 Digestion factors:
 Hydrochloric acid (protein;
enzymes activity;
i i bacteria)
b
i )
 Pepsin (protein digestion)
 Gastric lipase (Lipids)
 Gastrin (stimulate gastric
secretion and movement)
Muscular Action of Digestive Tract
Absorption in the Small Intestine
Villi
– Microvilli
– Capillaries and lacteals
– Chylomicrons
Crypts
Muscular Action of Digestive Tract - Peristalsis
Peristalsis
Segmentation
13
07-Apr-11
Muscular Action of Digestive Tract - Segmentation
From M to A: Digestion and Absorption
Large intestine colon
– Ileocecal valve
– Appendix
Rectum
– Anus
From M to A: Digestion and Absorption
From M to A: Digestion and Absorption
Small intestine
– Digestion
Bicarbonate
neutralizes
stomach acid
Pancreatic and
intestinal enzymes
– Carbohydrates
– Fat
– Protein
 Sphincter contractions
– Reflux (heart burn)
14
07-Apr-11
From M to A: Digestion and Absorption
Liver
– Bile - Emulsifier
Gallbladder
15
07-Apr-11
16