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Essential nutrients
- Nutrients required by an animal
- Include minerals and organic molecules that can't be produced by raw materials
- 4 classes
- Amino acids, fatty acids, vitamins, minerals
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Essential amino acids
- 10
- Must be obtained from food
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Essential fatty acids
- Must be ingested
- Ex, linoleic acid makes phospholipids in cell membrane
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Vitamins
Organic molecules required in the diet in small amounts
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Minerals
Simple inorganic nutrients that are required in the diet in small amounts
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4 main stages in food processing
- Ingesting
- Digesting
- Absorption
- Elimination
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Ingestion
The act of taking in food
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Digestion
- Breakdown of food into small molecules capable of being absorbed by the cells of the body.
- Enzymatic hydrolysis, breaking of bonds with the addition of a water molecule, is reaction type by which macromolecules are digested
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Absorption
Stage in food preceding when body's cells take up small molecules such as amino acids and simple sugars from the digestive tract
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Elimination
Passing of undigested material from the digestive tract
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Intracellular digestion
- Within a cell enclosed by a protective membrane
- Sponges
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Extracellular
- Most animals
- Food is broken down outside cells. Allows the animal to devour much larger sources of food
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Gastrovascular cavity
- Single opening through which food enters and waste exits.
- Cnidarians, flatworms
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Complete digestive tract (alimentary canals)
One way digestive tubes that begin at the mouth and terminate at the anus
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Peristalsis
- Rhythmic waves of contraction by smooth muscle in the walls of the alimentary canal
- Controls movement of food throughout digestive system
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Sphincters
Muscular, ring like valves that regulate the passage of material between digestive compartments
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Oral cavity
- Mouth
- Nervous reflex occurs that causes saliva, which lubricates the food to allow swallowing
- Starts chemical digestion
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Amylase
Enzyme in saliva which hydroxides starch and glycogen into smaller polysaccharides and maltose
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Bolus
Ball food is shaped into during chewing
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Pharynx
- Where bolus enters during chewing.
- Junction that opens to the esophagus and trachea
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Epiglottis
- Flap made of cartilage that covers the trachea during swallowing.
- Diverts food down esophagus, out of airway
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Esophagus
Moves food from the pharynx down to the stomach through peristalsis
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Gastric juice
- Digestive fluid
- Hydrochloric acid- pH 2, breaks down ECM of meat and plant materials, kills most bacteria ingested
- Pepsin- enzyme that begins to hydro lie proteins into smaller polypeptides.
- Secreted in inactive form pepsinogen, activated by Hydrochloric acid. Inactive form protects cells that produce digestion enzyme from self digestion.
- Thick mucus produced by lining of stomach
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Acid chyme
- Results from digestion in stomach.
- Shunted from stomach via pyloric sphincter
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Duodenum
- First section of small intestine.
- Major site of chemical digestion
- Acid chyme mixes with secretions from pancreas and liver. Pancreas releases bicarbonate fluid
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Bicarbonate fluid
- Produced by pancrease
- Acts as buffer against acidic contended from stomach
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Bile
- Meade in liver, stored in gall bladder
- Coats fat droplets turning large fat droplets into small fat droplets, which are easier to diget
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Carbohydrates
- Breakdown of starch and glycogen began with amylase.
- Small intestine, pancreatic amylases break down starch, glycogen, etc into monomers at wall of duodenal epithelium
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Proteins
- Pepsin begins breakdown
- Trypsin and chymotrypson brk polypeptides into smaller chains
- Dipeptodases break polypeptides into amino acids
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Nucleic acids
- Starts with hydrolysis of DNA and RNA into nucleotides.
- Nucleotides broken down into nitrogenous bases, sugars, and phosphate groups.
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Fats
- Digests starts in small intestine
- Bile coats fats, keeps them from clumping.
- Lipase, produced in pacrease, hydrolyzes small fat droplets
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Villi
Folds on epithelial lining of small intestine
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Microvilli
- Projections of villi
- Increase surface area available for absorption
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Lacteal
Capillaries on villi for absorption. Absorb small fatty acids
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Hepatic portal vessel
- Blood vessel that goes to liver, formed by capillaries and veins that drain nutrients away from villi.
- Liver then regulates distribution of nutrients
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Gastrin
- Produced by stomach
- Increases production of gastric juices
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Enterogastrone
- Produced by duodenum in presence of fats, slows peristalsis
- Allows more time for fat digestion
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Secretin and CCK
- Secreted by walls of duodenum
- Increase flow of digestive juices from pancreas and gall bladder
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Large intestine (colon)
- Connected to small intestine by a sphincter
- Cecum- point of connection site. Small pouch with extension called appendix
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Large intestine functions
- Compact waste
- recover water
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Rectum
- At end of colon
- Where feces is stored until it is eliminated
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Dentition
- Correlated with diet.
- Mammals have specialized that best enables them to ingest food
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