digestio nnew
DESCRIPTION
TRANSCRIPT
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DIGESTION
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What does the previous slide suggest?
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Digestion leads to the breakdown of the important substances needed by the body to grow and develop…..– Protein– Carbohydrates– Fats– Nucleic acids
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• Why does the plant need to eat a fly when it can undergo photosynthesis?
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Plant nutrition
• Plant are producers, they are ________.• Animals are _______, they are heterotrophic.– Heterotrophs are opportunistic feeders
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Digestion as an evolutionary evidence
• Compartmentalization• Mode of feeding• Mutualistic relationship
– Also presence of fats, why?
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Intracellular, extracellular and everything in between…..
• Intracellular– Food vacuoles, amoebocytes
• Extracellular– Incomplete vs complete digestive system
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Incomplete digestive system bridges…..
• Differs from complete because……• E.g. gastrovascular cavity of cnidarians• Gastrodermis- with specialized digestive cells
• HYDROLYSIS OF MACROMOLECULES IS INTRACELLULAR
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Gastrovascular cavity
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Complete
• Specialized compartment• Exit and entrance are different• Extracellular hydrolysis of food• Complexity varies
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Modes of Feeding
• Suspension feeders• Substrate feeders• Fluid feeders• Bulk feeders
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Symbiosis is nice…..
Evolution of symbiotic relationship with other organisms in processing food…. why is this needed?
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The four-chambered stomach of cows
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Four stages of food processing
• Ingestion– Large oral cavity
• Digestion– Mechanical vs chemical
• Absorption• Elimination
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The oral cavity or in short the mouth
• What is the mouth for?• Why do we need to produce saliva?• What is an enzyme and how does it help in
the digestion of food?
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Mechanical Digestion, what is it for?
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Pharynx
• Crossroad of food and air• Where bolus enters the esophagus• Epiglottis- flap that covers the entrance of air
when swallowing
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Epiglottis in action
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The esophagus
• Presence of striated and smooth muscle• Moves the bolus from pharynx to the stomach– peristalsis
• Presence of goblet cells
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Peristalsis
• Wave-like motion responsible for the movement of digested food in the alimentary canal
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The stomach
• Storage and digestion of food• Sphincters- regulate movement of bolus and
chyme• Which one has a larger stomach, a carnivore
or an herbivore? (pound-for-pound)
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Still on stomach…..
• Chief cells vs parietal cells• Pepsinogen and HCl follows a positive
feedback mechanism
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Ouch, my stomach hurts….
• Rapid mitotic activity• Activation of pepsin• Goblet cells
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Ouch, my heart burns!!!!
• Heart burn is not caused by the devil or your evil exes burning your heart, it is the result of the loosening of the valves
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Small intestine
• Main organ of digestion and absorption• Why is it the longest?• Divided into the duodenum, jejunum, ileum
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Absorption
• Villus- folds found in the small intestine
• Microvillus- microscopic fingerlike projections that increases the absorption of materials
• Each villus is connected to a capillary (BV) network and lacteals(Lymphatic system)
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RECITATION ON THE DIGESTION OF THE FOUR MACROMOLECULES
• Protein• Carbohydrates• Fats• Nucleic acids
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Hormones that regulate digestion
• Gastrin-stimulated by gastric juices– Inhibited by low pH– stimulates secretion of gastric juice
• Enterogastrones- group of enzymes found in the duodenum• Cholecystokinin (CCK)- stimulated by fats and amino acids
– Stimulates gall bladder to release bile• Secretin- stimulated by the acidic chyme
– Stimulates pancreas to release bicarbonates
– If chyme is rich in fats, it stimulates the duodenum to release other enzymes to slow down digestion in the stomach
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Large Intestine
• Also called the colon• Cecum – small pouch that has different fxns• Appendix- small cecum found in man• Rectum- portion of the large intestine that
temporarily stores feces• Main fxn of colon is to reabsorb water• Feces- waste that was formed after digestion
• Compactness depends on water that was reabsorbed
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Large Intestine
• Intestinal Bacteria- common example is E. coli
• Have mutualistic relationship with host
• Generate methane or hydrogen sulfide
• Some produce vitamins that are needed by the body
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Nutrition
• Nutritionally adequate diet– composed of:• fuel (chemical energy)• organic raw materials (carbon skeletons)• essential nutrients (substances the
animal cannot make)
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Balancing the fuel
• Homeostatic mechanism balances the animal’s fuel
• ATPs that were produced are budgeted depending on the energy requirements
• Fats have the highest amount of ATP• Glucose conversion is an example of
homeostatic mechanism
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Caloric Imbalance
• Undernourishment– Calorie deficiency
• Overnourishment– Excessive calorie intake- results to obesity
• Malnourishment– Deficient in any essential nutrients
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Essential Nutrients
• Essential Amino Acids• Essential Fatty Acids• Vitamins• Minerals
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Essential Amino Acids
• Tryptophan, methionine, Valine, Threonine, Phenylalanine, Leucine, Isoleucine, Lysine, Histidine (infants)
• Deficiency in one of these may result into protein deficiency
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Essential Fatty Acids
• Essential Fatty Acids belong to the unsaturated fatty acid groups
• An example is linoleic acid• Deficiencies are rare
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Vitamins
• Organic molecules that are required relatively in small amount
• Two types:– Water-soluble• B vits, C
– Fat-soluble• A, D, E, K
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Minerals
• Inorganic nutrients that are required in small amounts
• E.g. Calcium, Phosphorous, Sodium, etc.
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Balance diet
• what enters= what leaves• It is easier to take in calories in the body than
to burn it• The food pyramid serves as a guide in the kind of foods that should be taken in