26.1 Holozoic NutritionNutrition is the intake of food and processes of converting food substances into living matterPlants manufacture their own food – autotrophicAnimals cannot manufacture their own food, dependent on eating plants or other animals – heterotrophicMode of feeding organic matter is known as holozoic nutrition
36.1 Holozoic Nutrition Heterotrophic Nutrition Ingestion/Feeding – Taking food into bodyDigestionMechanical – chopping and grinding food with teeth and muscular churning of food, in stomachChemical – breaking large insoluble molecules into small, soluble ones (using enzymes)Absorption – taking digested food into bloodstreamAssimilation – using absorbed food in metabolic processesAny food which cannot be digested/absorbed is passed out of the gut during egestion
46.2 Mammalian Digestive System Consist of the gut (alimentary canal) and glands associated with it (9m long)Includes mouth, pharynx, oesophagus, stomach, small intestine and large intestineOther structures include salivary glands, pancreas, liver and gall bladder
56.2 Mammalian Digestive System The Mouth and buccal cavity Opening where food is ingested into buccal cavity (mouth cavity)Buccal cavity processes food:Teeth mechanically digest the food (increase surface area for enzymes to act on)Salivary glands secrete saliva containing enzyme salivary amylase to digest starch into maltoseTongue rolls the food into balls or boli (bolus) and pushes them to the back of the buccal cavity for swallowing
66.2 Mammalian Digestive System Pharynx Pharynx is the part of the gut leading from mouth to oesophagus and windpipeLarynx (voice box) which lies below pharynx has a slit-like opening called glottisPharynx is a passage for both food and air
76.2 Mammalian Digestive System Pharynx Food entering windpipe is prevented by a piece of flap-like cartilage called epiglottisEpiglottis is above larynx just behind root of tongueDuring swallowing, larynx moves up to be covered by epiglottis and thus preventing food from entering windpipeIf small particles get into the larynx or windpipe, violent coughing results to force them out and prevent choking
86.2 Mammalian Digestive System Oesophagus (Gullet) Muscular tube connecting mouth cavity and stomachWall of the oesophagus is made up of 2 layers of musclesThese muscles are present along the gut from the oesophagus to rectum
96.2 Mammalian Digestive System Oesophagus (Gullet) > Peristalsis The two layers of muscles cause rhytmic, wave-like contractions of the gut walls.This movement is known as peristalsisThis process enables:Enables food to be mixed with the digestive juicesMoves the food along the gutThe circular and longitudinal muscles are antagonistic muscles (one set of muscles contracts, other set relaxes)
106.2 Mammalian Digestive System Oesophagus (Gullet) > Peristalsis When circular muscles contract, longitudinal muscles relax wall of gut constricts becoming narrower and longer Food in gut is squeezed/pushed forwardWhen longitudinal muscles contracts, circular muscles relaxes Wall of gut dilates becoming wider and shorter Widens lumen for the food to enter
116.2 Mammalian Digestive System Oesophagus (Gullet) > Peristalsis
126.2 Mammalian Digestive System Stomach Distensible muscular bag with thick and well developed muscular wallsPeristalsis of stomach wall churns (mechanical digestion) food for up to 4 hours to mix with gastric juicesMucous coat of stomach wall has numerous pits that secrete gastric juices.Gastric juice consists of concentrated hydrochloric acid (pH2) and enzymes (rennin and pepsin)
136.2 Mammalian Digestive System Stomach > Hydrochloric Acid Hydrochloric acids:Stops action of salivary amylaseChanges inactive forms of enzymes in gastric juice to the active formsProvides an acidic medium suitable for the action of the gastric enzymesKills germs and certain potential parasites in food
146.2 Mammalian Digestive System Stomach Partly digested food becomes liquefied, forming chymeChyme passes in small amounts through a ring of muscle called the pylorus / pyloric sphincter, which relaxes to allow the food to enter the duodenum
156.2 Mammalian Digestive System Small Intestine Final place of digestionPlace where absorption of nutrients take placeConsists of: Duodenum, Jejunum, ileum
166.2 Mammalian Digestive System Small Intestine > Duodenum U-shapedFirst part of small intestine (most digestion occurs here)About 30m longReceives bile (produce by liver) via bile duct from gall bladder (stores bile)Receives pancreatic juice from pancreas, through pancreatic ductReleases digestive juice from its walls
176.2 Mammalian Digestive System Small Intestine > Duodenum Chyme stimulates intestinal glands to secrete intestinal juiceFood comes in contact with pancreatic juice, bile and intestinal juiceAll 3 fluids are alkaline which neutralize the acidic chyme and provide suitable alkaline medium for the action of pancreatic and intestinal enzymes
186.2 Mammalian Digestive System Small Intestine > Duodenum Pancreatic juice contains pancreatic amylase, pancreatic lipase and protease (trypsinogen)Intestinal juice contains enterokinase, erepsin (peptidase), maltase, sucrase, lactase, intestinal lipase
196.2 Mammalian Digestive System Large Intestine 1.5 m longConsists of : Colon, Rectum (stores faeces temporarily)Absorbs water and mineral saltsNo digestion takes place here
206.2 Mammalian Digestive System Organs and glands related gut > Liver Largest glandDark red with 5 lobesAttached with 3 blood vesselsHepatic portal vein: Transport digested products from intestines to liverhepatic vein: carries deoxygenated blood awayhepatic artery: carries oxygenated blood to liverSecretes bile (alkaline greenish-yellow fluid)
216.2 Mammalian Digestive System Organs and glands related gut > Gall Bladder Stores bile temporarilyGreenish yellow bag attached to liverContracts to release bile via bile duct into duodenum
226.2 Mammalian Digestive System Organs and glands related gut > Pancreas Connected to duodenum via pancreatic ductProduces pancreatic juice (Digestive enzymes)Pancreatic amylasePancreatic lipaseTrypsinogenSecretes hormones insulin and glucagon
236.3 DigestionA process where large insoluble molecules are broken down to smaller, soluble and diffusible molecules.It can be broken down as:Physical/MechanicalChemical
246.3 Digestion Physical Digestion Mechanical breakdown of food in:Mouth by the action of teeth (chewing)Stomach by churning of foodIncrease surface area to volume ratio for enzyme to acts on.
256.3 Digestion Chemical Digestion Breakdown of food involving hydrolytic reactions catalysed by enzymesTakes place in Mouth, Stomach, Small Intestine (SMS)
266.3 Digestion: The Digestive Process MouthBoth Physical and chemical processPhysical – chewing by teeth to increase surface area for enzyme to act onFood In mouth stimulates salivary glands to secrete salivaSalivary glands secrete saliva containing enzyme amylase to digest starch into maltose and protein mucinMucin is sticky thus binding food together and lubricates itpH 7
276.3 Digestion: The Digestive Process OseophagusNo digestion occurs herePeristalsis and gravity help to push food down to stomach.
286.3 Digestion: The Digestive Process StomachPhysical churning of foodChemical digestion (Digestion of proteins starts)Digested by proteases - rennin and pepsinCarbohydrates digestion stopsStomach contains gastric juice and it contains:Pepsin = digest proteins to polypeptidesRennin which clots or curdles milk proteins by converting soluble protein caseinogens into caseindilute hydrochloric acid
296.3 Digestion: The Digestive Process Stomach > Hydrochloric AcidStops action of salivary amylase by denaturing itChanges inactive forms of enzyme pepsinogen and prorennin in gastric juice to active forms pepsin and rennin respectively.Partly digested food in stomach is called chymeChyme passes into the duodenum when they pyloric sphincter relaxes and opens
306.3 Digestion: The Digestive Process Small IntestineChyme stimulates the release of 3 fluids into the duodenum:Pancreas secretes pancreatic juice into pancreatic ductIntestinal glands secrete intestinal juiceGall bladder releases bile into bile ductDigestion of Carbohydrate and protein continuesFat digestion starts
316.3 Digestion: The Digestive Process Pancreatic JuicePancreatic amylase which digests starch to maltoseTrypsin which digests proteins to polypeptides.Trypsin is produced as inactive trypsinogen are converted to the active trypsin by intestinal enetrokinaseLipase which digests fats to fatty acids and glycerolIntestinal JuiceMaltase which digests maltose to glucoseEnterokinase – Converting inactive trypsinogen to active trypsinErepsin – digest polypeptides to amino acidsLipase – digest fats to fatty acids and glycerolBileEmulsify (breaking down into smaller molecules) fats
326.3 Digestion : Carbohydrates StarchSalivary Amylase(In Mouth)MaltosePancreatic AmylaseNo digestion of starch in stomach (amylase are denatured)Maltose (in small intestine)Glucose
336.3 Digestion : Proteins Starts in stomach : acidic – pH2 Enzymes pepsin and rennin – pH 7Continues in small intestine : alkaline- pH9enterokinaseTrypsinogenTrypsinInSmall intestineTrypsinProteinsPolypeptidesErepsinPolypeptidesAmino acids
346.3 Digestion : Fats Starts in small intestine Bile emulsifies fats, i.e.: lowers the surface tension of fats and breaks them up into smaller fat globulesSurface area increased for action of lipasesFats + Bile EmulsionFatty Acids + GlycerolGall bladder secretes
356.4 Absorption Occurs in ileum Active transport takes place (requires energy)Rate of absorption depends on:Length of Small IntestineInner wall of intestine has numerous foldsPresence of villi (singular: villus)Presence of microvilli on villi
366.4 Absorption Villi have thin wall (one cell thick) Absorbed nutrients transported away quickly resulting in concentrating gradientAll these speeds up diffusion for efficient absorption.
376.4 AbsorptionSugar, amino acids and mineral salts pass into blood capillaries via process of active transportGlycerol and fatty acids enters into epithelium before combining into minute fat globulesFat globules enters the lacteals/ lympathic capillary.
386.4 Absorption Undigested and unabsorbed materials Stored temporarily in rectumDischarged as faeces through anusProcess of removal is known as egestion / defacation
396.5 Functions of Liver Regulate blood glucose level Production of bile Iron storageProtein synthesisDeamination of amino acidsDetoxification
406.5 Function of Liver Regulate blood glucose level When blood glucose is too high (especially after meal), liver alerts pancreasIslets of langerhans in pancreas will produce insulinInsulin convert glucose into glycogen.
416.5 Function of Liver Regulate blood glucose level GlycogenAfter LunchInsulinGlucoseBlood Glucose HighStored in Liver and MusclesLiverIslets of LangerhansPancreasHigh Blood Glucose Concentration
426.5 Function of Liver Regulate blood glucose level GlucagonGlucoseGlycogenLiver (Low blood glucose)PancreasIslets of LangerhansLow Blood Glucose Concentration
436.5 Function of Liver Production of Bile Helps in digestion fats (emulsifies fats)Stored temporarily in gall bladderProtein SynthesisForms amino acidsAlbumins, globulins, fibrinogen found in blood plasama
446.5 Functions of Liver Iron Storage Spleen (near liver) Destroys red blood cellsHaemoglobin in red blood cells destroyed by liver > Storing of IronBile pigments also formed during haemoglobin breakdown.
456.5 Function of Liver Deamination of Amino Acids Carbon ResidueAmino GroupconvertedconvertedAmmoniaGlucoseconvertedconvertedUreaGlycogen
466.5 Functions of Liver Detoxification Converting harmful substances in harmless ones.Example: Alcohol dehydrogenase (a type of enzyme) breaks down acetaldehyde in alcoholAlcohol stimulates secretion of stomach acid which may lead to stomach ulcersProlonged alcohol abuse may lead to cirrhosis (Damage of liver cells)