Digestive System

Digestive System

Stages of Food ProcessingIngestion- eating/feedingDigestion- food gets broken downMechanicalChemicalEnzymatic Hydrolysis: splitting process of chemical digestionIntracellular digestion: hydrolysis of food w/in vacuolesAbsorptionElimination

Intracellular disgestion occurs after phagocytosis or pinocytosis (cell eating and drinking)This brings food in contact with digestive enzymes

2Umbrella TermsGastrovascular cavity: digestive compartment w/ single openingAlimentary Canal: tube between two openings of an animal (AKA complete digestive tract)Food pushed along by peristalsis, using sphincters that acts as drawstrings

Peristalsis: alternating waves of contractiona dn relaxation in smooth muscles of the canal3IngestionOral cavity: start of ingestionSalivary glands: stimulated by presence of foodAmylase hydrolyzes starch and glycogenMechanical digestion shapes food into a bolusPharynx: throat cavityOpens to esophagus and tracheaEpiglottis flap covers opening to lungs when eatingLarynx guides movement of food into esophagus

Bolus: a ballEsophagus leads to stomachTrachea leads to lungsLarynx: upper part of the respiratory tract4DigestionStomach: stores food/starts protein digestionGastric juice: digestive fluidKept inactive until it reaches the lumen (cavity) of the stomachMixes w/ ingested food to create chymeHydrochloric acid denatures proteins in foodPepsin attacks exposed peptide bonds

Pepsin is a protease, or, protein digesting enzyme5AbsorptionSmall intestine: site of most enzymatic hydrolysis of macromoleculesDuodenum: formed by first 10 in of small intestineChyme mixes w/ more digestive juicesPancreas: produces enzymes and an alkaline solution w/ bicarbonatesLiver: produces bile (stored in the gallbladder) that digests lipids

Digestive juices from pancreas, liver, gallbladderBicarbonates act as a buffer that neutralizes the acidic chyme 6More AbsorptionVilli: finger like projections in the small intestine Surface has microvilliIncrease surface area for maximum absorptionHepatic portal vein: carries nutrient rich blood from villi to the liverLiver detoxifies and redistributes blood

Even more AbsorptionChylomicrons transported into a lacteal (vessel @ core of villus)water soluble globules fatty acids absorbed by small intestine epithelial cellsrecombined into triglycerides coated w/ lipids and proteinsGo into lymphatic system and eventually to the heartLets the lipids move in the water-based blood

ExcretionLarge intestine (end of alimentary canal)Cecum: pouch for fermentation; start of the large intestineColon: reabsorbs water; what we think of as the large intestineRectum: stores feces; end of the large intestine

:Small and large intestines join @ t shaped junctionOne arm is the colon which leads to the rectume and anusOther arm is the cecum: a puch used for fermenting ingested material9