Digestive System. Molecules DNA molecules Atoms Organ systems Cells nerve cell Tissues leaf tissues...
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Transcript of Digestive System. Molecules DNA molecules Atoms Organ systems Cells nerve cell Tissues leaf tissues...
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Digestive System
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MoleculesDNA molecules
Atoms
Organ systems
Cells
nerve cell
Tissuesleaf tissues
cardiactissue
Organismstree human
Organs
leaf
stem
brain
heart
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Cells require nutrients obtained from food and oxygen
The Digestive System will:
Disassemble large organic molecules into smaller component molecules
Transfer these to circulatory system for distribution to rest of body
Get rid of indigestible material
Functions of the Digestive System
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Mechanical Digestion: Grinding large food particles into smaller clumps (reducing # molecules per clump)
Chemical Digestion: Breaking larger molecules into smaller component molecules, by means of a chemical reaction, using enzymes
Absorption: Smaller component molecules transported across wall of digestive tract and into blood vessels
Elimination : getting rid of undigested food
Different steps of digestion
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Organs involved in digestion
Two types of organs:
Digestive Tract Organs
Accessory Organs
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Stomach
Oral cavity
Small intestine
Esophagus
Large intestine
Pancreas
Liver
Gall Bladder
Salivary glands Digestive tract
(Muscular tube w/ specialized segments)
Accessory glands
(secrete substances that aid with digestion)
Pharynx
Components of the digestive system
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Oral Cavity: Mechanical processing- chewing
Chemical Digestion- saliva secretion: carbohydrate digestion
• Epiglottis:
“Lid” that closes over opening to trachea - Prevents food entering airway
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Enzyme must bind to substrate, so enzyme must have access to these larger molecules.
Mechanical processing:
•increases surface area of food particles
•Exposes more molecules to enzymes, increases efficiency.
Why is mechanical processing important?
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Swallowing:
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Pharynx and Esophagus: No mechanical processing, digestion, or absorption, Merely conducts food to stomach.
If you stand on your head, will the food still move to your stomach?
YES: food moves down by muscle contractions of the esophagus (= peristalsis)
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Stomach: Storage for food
Mechanical processing: churning
Chemical digestion: protein digestion - enzymes secreted from stomach wall hydrochloric acid also secreted - Lowers pH to kill pathogens (disease-causing organisms) and activate protein enzymes
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Small Intestine:
Function:• Most chemical digestion
occurs in the small intestines (lipids, nucleic acids, carbohydrates, proteins)
• Absorption of nutrients
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Small Intestine:
From Accessory Organs:
• Bile produced in liver stored in gall bladder
• Pancreatic juices (enzymes)
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Digestion
Mechanical - Lipids not water soluble, but enzymes are - Bile will break up large groups of lipid molecules into smaller droplets so enzymes can act on them (Emulsification)
Bile enters the small intestine through the bile duct
Chemical - Carbohydrate, protein, & lipid digestion enzymes secreted from pancreas
enzymes located in the intestinal wall
Small Intestine:
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Small Intestine:
Absorption - Component molecules diffuse across intestinal wall into circulatory system
Villi(fingerlike projections)
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Increased surface area for absorption:
Intestinal wall - folded
Villi - Fingerlike projections of intestinal wall;
Microvilli - Projections of plasma membrane of intestinal cells
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Amino acids, glucose, other water soluble nutrients absorbed into the capillaries
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What are lacteals?
• Inside the villi are vessels of the lymphatic system that absorb the fatty acids and glycerol.
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Large Intestine (colon): - Absorbs water; - Contains lots of bacteria (mostly E. coli), bacteria digest some remaining food, bacteria produce vitamins; - Responsible for elimination of undigested food = feces)
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Blood leaving intestines is transported to the liver via the hepatic portal vein for processing [molecules modified, toxins removed]
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The liver Removes• unwanted or harmful chemicals (detoxification) including chemicals produced in the body, •unwanted chemicals taken into the body (e.g. carcinogens), and medications.
•Hepatocytes - Liver cells - the liver's main functional units.
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Pancreas
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Pancreas
•Main enzyme producing organ of digestive system• Pancreatic duct enters the small intestine to deliver fluid (pancreatic juice) through a small hole in the wall of the second part of the duodenum•Pancreatic juice contains enzymes capable of digesting all food types - protein, fat and carbohydrates
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