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Organization of the human body.
Name and define (6)
1) Chemical level: Atoms combine to form muolecules.
2) Cell level: Molecules form organelles, such as the nucleus and mitochondria which make up cells.
3) Tissue level: Similar cells and surrounding materials make up tissues.
4) Organ level: Different tissues combine to form organs; stomach.
5) Organ System level: Organs such as the stomach and inttestines make up an organ system.
6) Organism level: Organ systems make up on an organism.
Digestive Organ System
What does the GI tract contain, etc.
4) small intestine
5) large intestine
Liver, pancreas, and gall bladder:
inolved in digestion & metabolism of foods & nutrients.
Digestive System Overview
Digestion; Absorption (define)
Digestion: Process of breaking down foods into a form the body can use (able to absorb).
Absorption: Uptake of nutrients from the GI tract into the blood or lymph
Anatomy of the GI tract
(Name the four layers & define them.
: innermost layer; hollow part where food travels.
- Submucosa: contains blood vessels carrying nutrients.
- Muscle: move food forward through contractions (very coordinated)
outside layer-protects the tract.
(Diagram on slide 6)
Define Sphincters; the 5 types & there functions.
Ring like muscles that control the flow of contents in the GI tract.
1) Lower esophoageal sphincter: prevents backflow (reflux) of stomach contents into the esophogus.
(heartburn happens when not working)
2) Pyluric sphincter: Control the flow of stomach contents into the small intestine.
3) Sphincter of Oddi: Control the flow bile from common bile duct into the small intestine.
(used for fat absorption)
4) ileocecal sphincter: prevent the contents of the large intestine from remembering the small intestine.
5) Anal sphincters: Prevent defecation until person desires to do so.
*You have no control over sphincters
GI Motility. Name the 4 parts and there functions.
1) Peristalsis: contractions
2) Segmentation: back & forth
3) Mass movements: peristalsis over widespread area.
Digestive System Secretions
(secretion/ site of production/function)
Saliva, Mucus, Enzymes, Acid (HCL), Bile, Bicarbonate, Hormones.
Saliva (mouth): contributes to starch digestion.
Mucus (mouth, stomach, small/large intestine): Promotes GI tract cells, lubricates digesting food.
Enzymes (mouth, stomach small intestine, pancreas): Promotes digestion of carbs, fats, and protein into forms small enough for absorption.
Acid (stomach): promotes digestion of protein, destroys microorganisms, increases solubility of minerals.
Bile (liver, stored in gallbladder): Aids in fat digestion (emulsifies fat)
Bicarbonate (pancreas, small intestine): neutralizes stomach acid when it reaches small intestine.
Hormones (stomach, small intestine): regulates digestion and absorption.
What are considered very significant "workhorses" of digestion & metabolism?
Mouth (Oral cavity) Why do we chew food? What does food become after being mixed with saliva?
1) ability to swallow it
2) increase surface area, thus, increasing availability to enzymes.
*Mixed w/ saliva food becomes a bolus.
Name the 3 saliva components and there functions.
Lysosome: Breaks down bacteria.
Mucus: lubricates & holds bolus together.
Amylase: breaks down starch to sugar.
Taste & Smell.
Define the 5 tastes.
1) Salty (sodium)
2) Sour (acid)
3) Sweet (sugar)
4) Bitter (mostly phytochems. from plants)
5) Umami (variety of foods)
What are olfactory glands in the nose?
Used to smell.
Also has a big impact on taste.
*Supertasters, tasters, non-tasters
Define the function and part(s).
Swallowing: moves bolus from the mouth to the esophagus.
Epiglottis: prevents food from lodging in the trachea (i.e. windpipe)
Stomach (minor organ)
Describe the process after the esophagus.
1) Food bolus goes through lower esophageal sphincter into stomach.
2) Mixes w/ stomach secretions becomes chyme (very acidic)
3) Pyloric sphincter allows kyme into the small intestine.
4) Little absorption occurs in the stomach and only some digestion (not the primary site)
Types of stomach secretions (2)
- Hydrochloric acid (HCl):
- -very acidic
- -inactivates proteins
- -destroys bacteria & viruses
- -aids in mineral absorptions
- -converts to pepsinogens
Stomach secretions (cont'd) (3)
helps fat breakdown
hormone that controls release of HCl and pepsinogen.
protects the stomach from being digested.
- Regulated by prostaglandins (type of hormone)
- -Aspirin blocks prostaglandins & can lead to ulcers
Sections of the small intestine (most digestion occurs here) (4)
- Duodenum (10 in)
- Jejunum (4 ft.)
- Ileum (5 ft.)
- Lumen of the small intestine facilitates digestion & absorption due to villi & microvilli.
- (diagram on slide 19, ch.4)
Name the 4 hormones of the GI tract
2) Cholecystokinin (CCK)
4) Gastric inhibitory peptide (GIP)
Absorption: What are the 4 different ways of absorbing your food?
(primarily occurs in small intestine)
Passive Diffusion: nutrients in higher concentration in the lumen move to enterocytes that have lower cocentration (fats, water, & some nutrients)
facilitated diffusion: higher concentration to less plus a carrier protein or transporter to help get them across (fructose).
Active absorption: Is not dependent on concentration, requires ATP & a transporter (amino acids & glucose)
Endocytosis: engulfment (phagocytes)
Where does absorption take place? (3)
- 2) small intestine (most absorption)
- 3) large intestine
What systems are the nutrients regulated by? (2)
1) Cardiovascular system: includes heart, blood vessels & blood. Water soluable nutrients transported via capillaries in villi to portal vein --> liver.
2) Lyphatic system: includes lymph. Fat-soluble nutrients and large particles transported into the lyph vessels to thoracic duct (blood)