Digestive SystemDigestive System

I’m from Chiquita banana & I’m here to I’m from Chiquita banana & I’m here to say,say,

I’ve got a recipe for you today.I’ve got a recipe for you today.

You take a banana & you shove it down,You take a banana & you shove it down,

You wait a few minutes & it comes out You wait a few minutes & it comes out brown!brown!

http://www.gastrohttp://www.gastrolab.net/s92enjog.lab.net/s92enjog.htmhtmLet’s Tour The Let’s Tour The

Digestive System!Digestive System!

William BeaumontWilliam BeaumontFather of Gastric Father of Gastric

PhysiologyPhysiology Surgeon’s mate in US Surgeon’s mate in US

Army during War of Army during War of 18121812

Later observed musket Later observed musket wound in Alexis St. wound in Alexis St. Martin’s stomachMartin’s stomach Wound would not healWound would not heal Beaumont dangled food Beaumont dangled food

thru hole using stringthru hole using string 11stst person to observe person to observe

digestion in stomachdigestion in stomach Conclusions about Conclusions about

nature of gastric juice, nature of gastric juice, & observations of & observations of chemical digestionchemical digestion

http://www.james.com/bhttp://www.james.com/beaumont/dr_life.htmeaumont/dr_life.htm

Nutritional RequirementsNutritional Requirements All animals oxidize All animals oxidize

organic molecules in organic molecules in order to provide ATP for order to provide ATP for life processeslife processes Glucose is main fuel, but Glucose is main fuel, but

body may also use lipids & body may also use lipids & proteins-all under hormonal proteins-all under hormonal controlcontrol

Essential nutrients-Essential nutrients-organism cannot make, organism cannot make, must be taken in with must be taken in with foodfood Include amino acids, fatty Include amino acids, fatty

acids, vitamins (organic) & acids, vitamins (organic) & minerals (inorganic)minerals (inorganic)

Too few Too few calories=undernourishmecalories=undernourishmentnt

Too few essential Too few essential nutrients-malnourishmentnutrients-malnourishment

Feeding MechanismsFeeding Mechanisms Herbivores, Herbivores,

carnivores, omnivorescarnivores, omnivores Suspension feedersSuspension feeders

Sift from waterSift from water Substrate feedersSubstrate feeders

Live on or in food Live on or in food source, eat their way source, eat their way through itthrough it

Fluid feedersFluid feeders Suck nutrients from Suck nutrients from

host body fluidhost body fluid Bulk feedersBulk feeders

Eat relatively large Eat relatively large pieces of foodpieces of food

Stages of Food processingStages of Food processing Ingestion-chemical & Ingestion-chemical &

physicalphysical Mouth,teethMouth,teeth

Digestion-mechanical & Digestion-mechanical & chemicalchemical Breakdown food into Breakdown food into

smaller particlessmaller particles Saliva, gastric juice, Saliva, gastric juice,

accessory glands, teeth, accessory glands, teeth, peristalsisperistalsis

Absorption-keeping the Absorption-keeping the good stuffgood stuff Mainly sm. Intestine, water Mainly sm. Intestine, water

in colonin colon Elimination-getting rid of Elimination-getting rid of

the bad stuff, or excessthe bad stuff, or excess

Intracellular Intracellular digestiondigestion

Food broken down Food broken down in vacuoles, fused in vacuoles, fused w/ lysosomesw/ lysosomes

Heterotrophic Heterotrophic protists & spongesprotists & sponges

Extracellular digestionExtracellular digestion Food broken down Food broken down

outside cells in outside cells in compartments compartments continuous w/ the continuous w/ the outside environmentoutside environment gastrovascular gastrovascular

cavities(incomplete)-cavities(incomplete)-single openings, function single openings, function in digestion & in digestion & distributiondistribution

Alimentary canals Alimentary canals (complete)-2 openings(complete)-2 openings

More specialized, better More specialized, better isolation of enzymes, isolation of enzymes, ability to digest more ability to digest more food even if previous food even if previous food remains undigestedfood remains undigested

Comparative AnatomyComparative Anatomy

Crops-food storage(stomach)Gizzards-grind & fragment

Mammalian SystemMammalian System Breaks down food chemically & Breaks down food chemically &

physically/mechanicallyphysically/mechanically Mammalian digestive system is a complete Mammalian digestive system is a complete

system (alimentary canal)system (alimentary canal) Food only travels through one way(normally)Food only travels through one way(normally) Has 2 openings to external environment(mouth & Has 2 openings to external environment(mouth &

anus)anus) Vulnerable to outside pathogensVulnerable to outside pathogens

Digestive tract is completely isolated from the rest Digestive tract is completely isolated from the rest of the bodyof the body

Digestive enzymes can be isolatedDigestive enzymes can be isolated Toxins are kept away from rest of bodyToxins are kept away from rest of body

PeristalsisPeristalsis Smooth muscle along entire digestive tract Smooth muscle along entire digestive tract

contracts to move foodcontracts to move food

Pathway of FoodPathway of Food Oral cavity-mechanical & chemicalOral cavity-mechanical & chemical

Mastication-chewing-increases surface area for enzymesMastication-chewing-increases surface area for enzymes SalivaSaliva

Mucin-protects mouth & lubricatesMucin-protects mouth & lubricates Buffers-neutralize acid, prevent tooth decayBuffers-neutralize acid, prevent tooth decay Salivary amylase-hydrolyzes starch & glycogenSalivary amylase-hydrolyzes starch & glycogen

Tongue- tastes, shapes into bolus, pushes backTongue- tastes, shapes into bolus, pushes back Pharynx-intersection of digestive & respiratory systemsPharynx-intersection of digestive & respiratory systems

Epiglottis-cartilaginous flap that covers opening to trachea(glottis) Epiglottis-cartilaginous flap that covers opening to trachea(glottis) during swallowingduring swallowing

Esophagus-chemical digestion continues(salivary amylase)Esophagus-chemical digestion continues(salivary amylase) Top part contains voluntary, striated muscle, bottom has Top part contains voluntary, striated muscle, bottom has

smooth, involuntarysmooth, involuntary

Pathway of FoodPathway of Food Stomach-mechanical & chemicalStomach-mechanical & chemical

3 muscle layers contract to 3 muscle layers contract to break up food(longitudinal, break up food(longitudinal, vertical, diagonal)vertical, diagonal)

Cardiac sphincter-between Cardiac sphincter-between esophagus & stomachesophagus & stomach

Gastric juice-secreted by Gastric juice-secreted by epithelial cellsepithelial cells

HCL-disrupts ECM to break HCL-disrupts ECM to break up plant & animal tissue, kills up plant & animal tissue, kills bacteriabacteria

Pepsin-protein hydrolysisPepsin-protein hydrolysis Mucus-protects lining from Mucus-protects lining from

HCLHCL End product of stomach End product of stomach

process results in a mixture process results in a mixture called acid chymecalled acid chyme

Cells of stomach liningCells of stomach lining Mucus cells-mucin & gastrinMucus cells-mucin & gastrin Chief cells-Chief cells-

pepsinogen(inactive) pepsinogen(inactive) converted to pepsin by HCLconverted to pepsin by HCL

Parietal cells-HCLParietal cells-HCL Pyloric sphincter-between Pyloric sphincter-between

stomach & small intestinestomach & small intestine

ulcer

Pathway of FoodPathway of Food

Small intestine-21 ft longSmall intestine-21 ft long Major site of digestion(duodenum) & absorption (jejunum & ileum)Major site of digestion(duodenum) & absorption (jejunum & ileum) Structure(see fig. 41.15)Structure(see fig. 41.15)

Villi & microvilli increase surface area for absorptionVilli & microvilli increase surface area for absorption Capillary & lacteal in each villiCapillary & lacteal in each villi

Duodenum-1Duodenum-1stst 25cm 25cm Functions in breakdown of lipids, CBH, & proteins-most Functions in breakdown of lipids, CBH, & proteins-most

digestion takes place heredigestion takes place here Secretes its own enzymes, & also receives enzymes from Secretes its own enzymes, & also receives enzymes from

accessory glandsaccessory glands Jejunum & ileum-function in absorbing nutrients-diffusion & Jejunum & ileum-function in absorbing nutrients-diffusion &

active transportactive transport All capillaries from small intestine pass into hepatic portal vein All capillaries from small intestine pass into hepatic portal vein

& go to liver before anywhere else!!& go to liver before anywhere else!!

Pathway of FoodPathway of Food Colon/large intestineColon/large intestine

Ascending, transverse, Ascending, transverse, descendingdescending

Cells absorb water back Cells absorb water back into body, and produce into body, and produce mucus to lubricatemucus to lubricate

Contains high amount of Contains high amount of bacteria to aid in bacteria to aid in digestiondigestion

Appendix-remnant of Appendix-remnant of large cecum in large cecum in herbivoresherbivores

Rectum-stores feces Rectum-stores feces before eliminationbefore elimination

Anus-Anus- 2 sphincter muscles-1 2 sphincter muscles-1

voluntary, 1 involuntaryvoluntary, 1 involuntary

Enzymatic DigestionEnzymatic Digestion

Accessory OrgansAccessory Organs PancreasPancreas

Secretes enzymes into sm. Int., regulates Secretes enzymes into sm. Int., regulates blood sugarblood sugar

Gall bladderGall bladder Stores liver secretions (bile) for fat Stores liver secretions (bile) for fat

digestiondigestion Secretes into duodenumSecretes into duodenum

LiverLiver Produces bile salts, regulates cholesterol, Produces bile salts, regulates cholesterol,

stores fat soluble vitamins, breaks down Hb stores fat soluble vitamins, breaks down Hb into bilirubin, regulates blood sugarinto bilirubin, regulates blood sugar

Digestive HormonesDigestive Hormones

GastrinGastrin Secreted by cells of stomach wallSecreted by cells of stomach wall Stimulates gastric juiceStimulates gastric juice

SecretinSecretin Cells of duodenumCells of duodenum Stimulates pancreas to release Stimulates pancreas to release

bicarbonatebicarbonate CholecystokininCholecystokinin

Cells of duodenumCells of duodenum Causes gall bladder to release bileCauses gall bladder to release bile