1、Human DigestionNutrition Process by which organisms obtain and utilize their food.There are two parts to Nutrition:1.Ingestion-process of taking food into the digestive system so that it may be hydrolized or digested.2.Digestion-the breakdown of food(either chemically or mechanically)in order to uti
2、lize nutrientsTypes of Nutrients Micronutrients-vitamins,minerals,&water Macronutrients-proteins,lipids,carbohydrates,etcHuman digestive systemGI(gastrointestinal)tract=alimentary canal Ingestion Mouth mechanical digestion teeth breaking up food chemical digestion saliva amylase enzyme digests starc
3、h 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 foodmouth break up food digest starch kill germs moisten foodMouth Chemical and m
4、echanical digestion.Food is chewed(masticated)mechanically.A bolus(lump)is formed with saliva and the tongue.Swallowing(¬ choking)Epiglottis flap of cartilage closes trachea(windpipe)when swallowing food travels down esophagus Peristalsis involuntary muscle contractions to move food along Which t
5、ype of digestion is the following?1.Chewing a saltine?-2.Saliva breaking the saltine down into molecules of glucose?-3.Your tongue breaking pieces of a hamburger apart?4.Pepsin(an enzyme)in your stomach breaking the hamburger into amino acids?Pharynx The back of the throat.Larynx-passage for air,clo
6、ses when we swallow.Is approximately 15cm long.Digestive Glands Groups of specialized secretory cells.Found in the lining of the alimentary canal or accessory organs.series of involuntary wave-like muscle contractions which move food along the digestive tractPeristalsisStomach Food is temporarily st
7、ored here.Gastric juices are secreted.Has layers of muscle that line the inside.Mechanically and chemically breaks down food.Stomach Functionsfood 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 ou
8、t of protein!What stops the stomach from digesting itself?mucus secreted by stomach cells protects stomach liningstomach kills germs break up food digest proteins store foodsphinctersphinctermouth break up food digest starch kill germs moisten foodGastric Juices Secreted by the stomach.Acidic(pH 1.5
9、-2.5)(HCl).Pepsin-an enzyme that breaks down large proteins into amino acids.Food is further broken down into a thin liquid called chyme.Accessory Organs Pancreas Gall Bladder SpleenGall bladder Pouch structure located near the liver which concentrates and stores bile Bile duct a long tube that carr
10、ies BILE.The top half of the common bile duct is associated with the liver,while the bottom half of the common bile duct is associated with the pancreas,through which it passes on its way to the intestine.BILE Bile emulsifies lipids(physically breaks apart FATS)Bile is a bitter,greenish-yellow alkal
11、ine fluid,stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.Pancreas An organ which secretes both digestive enzymes(exocrine)and hormones(endocrine)*Pancreatic juice digests all major nutrient types.Nearly all digestion occ
12、urs in the small intestine&all digestion is completed in the SI.Pancreas Digestive enzymes digest proteins trypsin,chymotrypsin digest starch amylase Buffers neutralizes acid from stomachLiver Function produces bile bile stored in gallbladder until needed breaks up fats act like detergents to breaku
13、p fatsbile contains colors from old red blood cells collected in liver=iron in RBC rusts&makes feces brownpancreas produces enzymes to digest proteins&starchstomach kills germs break up food digest proteins store foodmouth break up food digest starch kill germs moisten foodliver produces bile-stored
14、 in gall bladder break up fatsSmall Intestine Most chemical digestion takes place here.Simple sugars and proteins are absorbed into the inner lining.Fatty acids and glycerol go to lymphatic system.Lined with villi,which increase surface area for absorption,one cell thick.Small intestine Function che
15、mical 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&waterDuodenum 1st section of s
16、mall intestines acid food from stomach mixes with digestive juices from:pancreas liver gall bladderstomach kills germs break up food digest proteins store foodmouth break up food digest starch kill germs moisten foodpancreas produces enzymes to digest proteins&starchAbsorption in the SI Much absorpt
17、ion is thought to occur directly through the wall without the need for special adaptations Almost 90%of our daily fluid intake is absorbed in the small intestine.Villi-increase the surface area of the small intestines,thus providing better absorption of materialsAbsorption by Small Intestines Absorp
18、tion through villiµvilli finger-like projections increase surface area for absorptionVILLILarge intestines(colon)Function re-absorb water use 9 liters of water every day in digestive juices 90%of water reabsorbed not enough water absorbed diarrhea too much water absorbed constipationLarge Intes
19、tine Solid materials pass through the large intestine.These are undigestible solids(fibers).Water is absorbed.Vitamins K and B are reabsorbed with the water.Rectum-solid wastes exit the body.Youve got company!Living in the large intestine is a community of helpful bacteria Escherichia coli(E.coli)pr
20、oduce vitamins vitamin K;B vitamins generate gases by-product of bacterial metabolism methane,hydrogen sulfideAppendixVestigial organRectum Last section of colon(large intestines)eliminate feces undigested materialsextracellular wastemainly cellulose from plantsroughage or fiber masses of bacteriaDi
21、gestive Homeostasis Disorders ULCERS erosion of the surface of the alimentary canal generally associated with some kind of irritant a condition in which the large intestine is emptied with difficulty.Too much water is reabsorbed and the solid waste hardensDigestive Homeostasis DisordersDigestive Hom
22、eostasis Disorders DIARRHEA a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.This results in increased,multiple,watery feces.This condition may result in severe dehydration,especially in infantsDigestive Homeostasis
23、Disorders APPENDICITIS an inflammation of the appendix due to infection Common treatment is removal of the appendix via surgeryDigestive Homeostasis Disorders GALLSTONES an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder Can either be“passed”(OUCH!)or surgically remov
24、edDigestive Homeostasis DisordersANOREXIA NERVOSA-a psychological condition where an individual thinks they appear overweight and refuses to eat.Weighs 85%or less than what is developmentally expected for age and height Young girls do not begin to menstruate at the appropriate age.Digestive Homeostasis Disorders HEART BURN ACID from the stomach backs up into the esophagus.
