The digestivesystem
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The digestivesystem






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The digestivesystem The digestivesystem Presentation Transcript

  • Human Digestion
  • NutritionProcess by which organisms obtain and utilize their food.There are two parts to Nutrition:1. Ingestion- process of taking food into thedigestive system so that it may behydrolized or digested.2. Digestion- the breakdown of food (eitherchemically or mechanically) in order toutilize nutrients
  • Types of Nutrients• Micronutrients- vitamins, minerals, & water• Macronutrients- proteins, lipids,carbohydrates, etc…
  • Human digestivesystem
  • GI (gastrointestinal) tract = alimentary canal
  • Ingestion• Mouth– mechanical digestion• teeth– breaking up food– chemical digestion• saliva– amylase» enzyme digests starch– mucin» slippery protein (mucus)» protects soft lining of digestive system» lubricates food for easier swallowing– buffers» neutralizes acid to prevent tooth decay– anti-bacterial chemicals» kill bacteria that enter mouth with food
  • mouthbreak up fooddigest starchkill germsmoisten food
  • Mouth• Chemical andmechanicaldigestion.• Food is chewed(masticated)mechanically.• A bolus (lump) isformed with salivaand the tongue.
  • Swallowing (& not choking)• Epiglottis– flap of cartilage– closes trachea (windpipe) when swallowing– food travels down esophagus• Peristalsis– involuntary muscle contractions to move food along
  • Which type of digestion is thefollowing?1. Chewing a saltine? -2. Saliva breaking the saltine down into molecules ofglucose? -3. Your tongue breaking pieces of a hamburger apart?4. Pepsin (an enzyme) in your stomach breaking thehamburger into amino acids?
  • Pharynx• The back of thethroat.• Larynx-passage for air,closes when weswallow.• Is approximately15cm long.
  • Digestive Glands• Groups ofspecializedsecretorycells.• Found in thelining of thealimentarycanal oraccessoryorgans.
  • • series of involuntarywave-like musclecontractions whichmove food along thedigestive tractPeristalsis
  • Stomach• Food is temporarilystored here.• Gastric juices aresecreted.• Has layers ofmuscle that line theinside.• Mechanically andchemically breaksdown food.
  • Stomach• Functions– food storage• can stretch to fit ~2L food– disinfect food• HCl = pH 2– kills bacteria– chemical digestion• pepsin– enzyme breaks down proteinsBut the stomach is made out of protein!What stops the stomach from digesting itself?mucus secreted by stomach cells protectsstomach lining
  • stomachkills germsbreak up fooddigest proteinsstore foodsphinctersphinctermouthbreak up fooddigest starchkill germsmoisten food
  • Gastric Juices• Secreted by thestomach.• Acidic (pH 1.5-2.5)(HCl).• Pepsin- an enzyme thatbreaks down largeproteins into aminoacids.• Food is further brokendown into a thin liquidcalled chyme.
  • Accessory Organs• Pancreas• Gall Bladder• Spleen
  • Gall bladder• Pouch structure located near the liverwhich concentrates and stores bile• Bile duct – a long tube that carries BILE.The top half of the common bile duct isassociated with the liver, while the bottomhalf of the common bile duct is associatedwith the pancreas, through which it passeson its way to the intestine.
  • BILE• Bile emulsifies lipids (physically breaksapart FATS)• Bile is a bitter, greenish-yellow alkalinefluid, stored in the gallbladder betweenmeals and upon eating is discharged intothe duodenum where it aids the process ofdigestion.
  • Pancreas• An organ which secretes both digestiveenzymes (exocrine) and hormones (endocrine)• ** Pancreatic juice digests all major nutrienttypes.• Nearly all digestion occurs in the small intestine& all digestion is completed in the SI.
  • Pancreas• Digestive enzymes– digest proteins• trypsin, chymotrypsin– digest starch• amylase• Buffers– neutralizesacid fromstomach
  • Liver• Function– produces bile• bile stored in gallbladder until needed• breaks up fats– act like detergents to breakup fatsbile containscolors from oldred blood cellscollected in liver =iron in RBC rusts &makes feces brown
  • pancreasproduces enzymes todigest proteins & starchstomachkills germsbreak up fooddigest proteinsstore foodmouthbreak up fooddigest starchkill germsmoisten foodliverproduces bile- stored in gall bladderbreak up fats
  • Small Intestine• Most chemicaldigestion takes placehere.• Simple sugars andproteins are absorbedinto the inner lining.• Fatty acids andglycerol go to lymphaticsystem.• Lined with villi, whichincrease surface area forabsorption, one cellthick.
  • Small intestine• Function– chemical digestion• major organ of digestion & absorption– absorption through lining• over 6 meters!• small intestine has huge surface area = 300m2(~size of tennis court)• Structure– 3 sections• duodenum = most digestion• jejunum = absorption of nutrients & water• ileum = absorption of nutrients & water
  • Duodenum• 1st section of small intestines– acid food from stomach– mixes with digestive juices from: pancreas liver gallbladder
  • stomachkills germsbreak up fooddigest proteinsstore foodmouthbreak up fooddigest starchkill germsmoisten foodpancreasproduces enzymes todigest proteins & starch
  • Absorption in the SI• Much absorption is thought to occur directly through the wallwithout the need for special adaptations• Almost 90% of our daily fluid intake is absorbed in the smallintestine.• Villi - increase the surface area of the small intestines, thusproviding better absorption of materials
  • Absorption by Small Intestines• Absorption through villi & microvilli– finger-like projections– increase surface area for absorption
  • Large intestines(colon)• Function– re-absorb water• use ~9 liters of water everyday in digestive juices• > 90% of water reabsorbed– not enough water absorbed» diarrhea– too much water absorbed» constipation
  • Large Intestine• Solid materials passthrough the largeintestine.• These are undigestiblesolids (fibers).• Water is absorbed.• Vitamins K and B arereabsorbed with thewater.• Rectum- solid wastesexit the body.
  • You’ve got company!• Living in the large intestine is acommunity of helpful bacteria– Escherichia coli (E. coli)• produce vitamins– vitamin K; B vitamins• generate gases– by-product of bacterial metabolism– methane, hydrogen sulfide
  • AppendixVestigial organ
  • Rectum• Last section of colon(large intestines)– eliminate feces• undigested materials– extracellular waste» mainly cellulosefrom plants» roughage or fiber– masses of bacteria
  • Digestive Homeostasis Disorders• ULCERS – erosion of the surface of thealimentary canal generally associatedwith some kind of irritant
  • • CONSTIPATION – acondition in which thelarge intestine is emptiedwith difficulty.• Too much water isreabsorbed• and the solid wastehardensDigestive Homeostasis Disorders
  • Digestive HomeostasisDisorders• DIARRHEA – a gastrointestinaldisturbance characterized bydecreased water absorption andincreased peristaltic activity ofthe large intestine.• This results in increased,multiple, watery feces.• This condition may result insevere dehydration, especially ininfants
  • Digestive HomeostasisDisorders• APPENDICITIS – an inflammation ofthe appendix due to infection• Common treatment is removal of theappendix via surgery
  • Digestive HomeostasisDisorders• GALLSTONES – an accumulation ofhardened cholesterol and/or calciumdeposits in the gallbladder• Can either be “passed” (OUCH!!) orsurgically removed
  • Digestive HomeostasisDisorders• ANOREXIA NERVOSA - a psychologicalcondition where an individual thinks theyappear overweight and refuses to eat.• Weighs 85% or less than what isdevelopmentally expected for age andheight• Young girls do not begin to menstruate atthe appropriate age.
  • Digestive HomeostasisDisorders• HEART BURN – ACID from thestomach backs up into the esophagus.
  • Let’s go to the Video!QuickTime™ and adecompressorare needed to see this picture.
  • Digestive System CadaverQuickTime™ and adecompressorare needed to see this picture.
  • Travel Through the DigestiveSystemQuickTime™ and adecompressorare needed to see this picture.