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Unit 3. NUTRITION AND DIGESTION. 3.1WHAT IS NUTRITION?. The process of nutrition allows living beings to obtain the matter and the energy they need for making their own matter and for carrying out their vital functions . 3.2 KINDS OF ORGANISMS ACCORDING TO NUTRITION.
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Unit 3 NUTRITION AND DIGESTION
Theprocess of nutritionallows living beingstoobtainthematter and theenergytheyneedformakingtheirownmatter and forcarryingouttheir vital functions.
Living beings can be placed intotwogroupsaccordingtowhattheyneedfromtheenvironment: • Producer organisms:theytakeinorganicsubstancesfromtheenvironment. Theyalsoneed a source of energythatthey can use. Example: photosynthesis→sunlight. • Consumerorganisms: theyneedtotakefoodfromtheenvironment, thisisalwaysorganicmatteralreadyformedbyother living beings.
Theprocess of nutritionmeansthatvarioussubstancesentertheorganism and otherdifferentsubstances are expelledeitherbecausetheyaren´tusefulorbecausethey are toxic.
Theprocessesrelatedtonutrition are carriedoutbyfourorgansystems in ourbody: thedigestivesystem, therespiratorysystem, thecirculatorysystem and theexcretorysystem. Allthesesystems and processes are controlledbythenervoussystem.
THE SYSTEMS RELATED TO NUTRITION Respiratorysystem Digestivesystem Circulatorysystem Excretorysystem
Animalsobtainproteins, lipids and sugarsfromfood. Thisis a verydifficulttask and itis done bythedigestivesystem. There are threephases in foodprocessing: digestion, absorption and theexpulsion of waste.
Themovement of foodthroughthedigestivetractis done thankstoperistalticmovements. Theseconsist of thenarrowing of thetubethroughthecontraction of themuscles of thewalls. Themusclescontractsuccessively in such a waythattheprogressivenarrowingpushesthefoodregardless of the position of thebody. Onocassion, such as vomiting, reverse peristalticmovementsoccur.
Accordingtothechanges in food, digestion can be: • Mechanical:Itconsists of cutting, crushing, removing and dilutingfoods, bringingaboutphysicalchanges. • Chemical:Itis done throughtheaction of varioussubstanceswhichattackthefood and bringaboutchemicalchanges in it, breakingitdownintosubstanceswhich are smaller.
Digestion in themouthis a result of mastication and salivation. Masticationcuts and crushesthefood. Salivais a liquidwhichisproducedbythesalivaryglands in themouth, there are threepairs of glandscalledthe sublingual, thesubmaxilary and theparotoidglands. Saliva containssubstanceswhichactchemicallyonfood.
Afterswallowing, foodreachesthestomachwheregastricdigestionbegins. Physical and chemicaldigestionalsooccursimultaneously in thestomach. Thefoodmoves and issoftenedthankstothemovement of thewalls of thestomach and itismixedwithgastricjuices. As a result of gastricdigestion, a pulpknown as chymeisproduced and thisgraduallyleavesthestomachviathepylorus.
Thefirstsection of thesmallintestine, theduodenum, continuesthechemicaldigestion of thefood. There, thechymeismixedwithintestinal juices (madebythewalls of theduodenum), bile (producedbytheliver) and pancreaticjuice (fromthepancreas). Theresultis a milky fluid known as chyle in whichthesubstancesthatthebody can assimilatehavebeenseparated.
Thechylepassesfromtheduodenumtothefollowingparts of thesmallintestine, thejejunum and theileum. The intestinal walls are very rough and filledwith intestinal hairs, deepfolds in thewall and manybloodvessels.
Theabsorptionconsists of theusefulsubstances in thefoodcrossingthroughthe intestinal wall and intothebloodvessels. Thebloodthentakesthemtoallthecells in thebody.
Theremains of thechylewhich can notbeusedpassintothelargeintestine. In thefirstpart, theascending colon, beginstorecoverwater and someions. Thisprocesscontinues in thetransverse colon. The final tract of thelargeintestineisthedescending colon whichstoresthefaeces. When a certainamount has beenformed, thefaecespasstotherectumreadytobeexpelledviatheanus.
Mouth • Liver • Gallbladder • Vermiformappendix • Anus • Largeintestine: ascending colon (), transverse colon () and descending colon() • Small intestine: duodenum (), jejunum () and ileum () • Spleen • Stomach • Pancreas • Pharynx • Oesophagus • Salivaryglands • Rectum
teeth Thetooth formula is 4I+2C+4PM+6M per jaw. Adultshave a total of 32 teeth. Thethird molar, alsocalledthewisdomtooth, appears in adult-hood.
Molar 3rd (Wisdomtooth) • Molar 2nd • Molar 1st • Pre-molar 2nd • Pre-molar 1st • Canine • Incisors
Oesophagus • Loweroesophagealsphincter • Cardia • Stomachfundus • Gastricfolds • Stomach, greatercurvature • Stomach, lessercurvature • Layers of thewall of thestomach (): mucus tunic (), muscular tunic () and seroustunic () • Pylorus • Initialstage of theduodenum
Associatedglands and theduodenum Theliver and thepancreas share the final stage of thebileductwhichreleasestheproducts of bothglands (bile and gastricjuices) intotheduodenum. Thisduct opens intotheduodenumthroughwhatisknown as theampulla of Vater
Stomach • Pancreas • Liver • Duodenum • Gallbladder • Cysticconduct • Bileduct • Pancreaticduct • Ampulla of Vater
Nutrition • Mechanicaldigestion • Chemicaldigestion • Mastication • Saliva • Chyme • Chyle
Nutrition: Itistheprocessthatallows living beingstoobtainthematter and theenergytheyneedformakingtheirownmatter and forcarryingouttheir vital functions. • Mechanicaldigestion: Itconsists of cutting, crushing, removing and dilutingfoods, bringingaboutphysicalchanges. • Chemicaldigestion:Itis done throughtheaction of varioussubstanceswhichattackthefood and bringaboutchemicalchanges in it, breakingitdownintosubstanceswhich are smaller.
Mastication:Itis a process in whichthefoodiscut and crushed. • Saliva:Itis a liquidwhichisproducedbythesalivaryglands in themouth and containssubstanceswhichactchemicallyonfood. • Chyme:Itis a pulpformedbyfood and gastricjuiceswhichistheresult of gastricdigestion. • Chyle:Itis a milky fluid formedbythechymemixedwith intestinal juices, bile and pancreaticjuice, in whichthesubstancesthatthebody can assimilatehavebeenseparated.
TMUOH • ILVRE • GLAL BEADLDR • VOMERIFRM NAXPEPDI • UASN • OAGESPHOUS • ALSVAIRY NGADLS • URCTEM • SOACTMH • ENPARASC • YPNARXH
ELRAG NTNETISEI • EDSCDINGEN OLCON • SMALL IENESTITN • DEOUDNMU • AICNSDNGE OCONL • UJUNJME • ILMEU • NTVASERSRE LCONO • LSEPEN