digestion
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DIGESTION. The process of preparing your food for absorption - PowerPoint PPT PresentationTRANSCRIPT
DIGESTION
The process of preparing your food for absorption
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What Happens to the Food We Eat?
Digestion
To break nutrients into smaller moleculesPhysical DigestionMechanical breakdown of food particlesChemical DigestionEnzyme catalyzed breakdown of nutrient molecules
Absorption
Movement of digested nutrients through intestinal wall into:Blood (water soluble nutrients)Lymphatic system - > blood (fat soluble nutrients
Digestion:The Mouth
Chewing: physically breaks down food into smaller componentsFood stimulates salivary glands to release saliva– Saliva contains amylase-breaks down starch– Saliva moistens food for easy swallow
Bolus: ball of chewed food mixed with saliva
DIGESTION:THE PHARYNX
Area responsible for swallowingDuring swallowing, air passage is blocked by epiglottis– Blocks the food from entering the trachea and the
lungs– Bolus is directed down the esophagus
DIGESTION:THE ESOPHAGUS
Connects the pharynx and the stomachBolus is moved towards the stomach by a contractile movement called peristalsisAllows food to move through thoracic cavity, through diaphragm, to peritoneal cavity and the stomach (peristalsis)
Digestion: Chewing
Digestion: Swallowing
Digestion: Swallowing
DIGESTION:THE STOMACH
Food passes through a sphincter, (esophageal sphincter) a valve Bolus mixes with stomach secretions to become chymeHCl denatures proteins and kills bacteriaMucus protects stomach wall from acidChyme released into small intestine through pyloric sphincter
DIGESTION:STOMACH
Stops salivary amylase and and slows lingual lipase activity (acid denatures enzyme)Starts protein digestion: pepsin activated and starts protein digestion Two Australians win Nobel Prize in medicine - More Health News - MSNBC.com
Digestion: The Stomach
DIGESTION:SMALL INTESTINE
20 feet in lengthdivided into three segments: – duodenum– jejunum– ileum
95% of digestion occurs in small intestineBile: made in liver, stored in gall bladder– Emulsifies fats
Digestion: Accessory Organs
Absorption
DIGESTION:SMALL INTESTINES
Pancreas: – Secretes bicarbonate into duodenum to neutralize
stomach acid in the chyme– Secretes enzymes that act on
• protein (proteases)• carbohydrate (carbohydrases)• lipids (lipases)
DIGESTION:LARGE INTESTINES
Absorbs water and some mineralsSupports growth of bacteria that produce Vitamin KSupports growth of other bacteria that partially breaks down fiber– We are then able to absorb some of the breakdown
products
Absorption and Transportation
All nutrients must pass through intestinal liningPicked up by capillaries or lymphatic vessels
DIGESTION:CARBOHYDRATES
Begins in the mouth: salivary amylase– Amylase denatured in stomach
Small intestine: pancreatic enzymes breakdown large CHO’s(starch) to smallerSmall intestines: brush border cells produce disaccharidases (sucrase, maltase, lactase)– Breakdown sucrose, maltose, lactose
Absorption occurs in duodenum & jejunum
DIGESTION:PROTEIN
Protein digestion begins in the stomach– Denaturation by HCl– Pepsin breaks large proteins into smaller peptides
Pancreatic enzymes introduced into the duodenum– Break down peptides into amino acids, di- and tri-
peptides– Intestine enzymes breakdown to amino acids
DIGESTION:LIPIDS
Mouth: Lingual Lipase, very little activityStomach: very little activitySmall Intestines: Major activity– Bile from gall bladder emulsifies– Enzymes from pancreas digest and makes the
products ready for digestion• monoglycerides, glycerol, fatty acids• absorbed into cells of microvilli
Other Systems
CardiovascularHormonal and NervousStorage– Liver– Muscle– Fat