Digestive SystemDigestive System

Do It NowDo It Now1. What are the two functions of an animal 1. What are the two functions of an animal

digestive system? (2 points)digestive system? (2 points)2. Write the following in correct order and 2. Write the following in correct order and

briefly list its function:briefly list its function:Anus, rectum, mouth, stomach, esophogus, Anus, rectum, mouth, stomach, esophogus,

small intestine, large intestine (16 points)small intestine, large intestine (16 points)3. Where are villi and microvilli found? (1 point)3. Where are villi and microvilli found? (1 point)4. What is the function of villi and micro villi? 4. What is the function of villi and micro villi?

(1 point)(1 point)Extra credit: What is chyme?Extra credit: What is chyme?

Collect 24 hours dataCollect 24 hours data

Decant liquid down the drain.Decant liquid down the drain.Throw away bag.Throw away bag.

Put stuff back where you got it!!!Put stuff back where you got it!!!

FunctionFunction

Take in foodTake in food Process food - DigestionProcess food - Digestion Absorb nutrientsAbsorb nutrients

Homeostasis of Blood GlucoseHomeostasis of Blood Glucose

What are the two main What are the two main nutrients carried by blood nutrients carried by blood for cellular respiration?for cellular respiration?

Why must blood glucose Why must blood glucose levels be maintained at a levels be maintained at a certain level?certain level?

NutritionNutrition

Animals must supply carbon Animals must supply carbon skeletons necessary to build all skeletons necessary to build all needed molecules.needed molecules.

Animals must supply themselves Animals must supply themselves with essential nutrients that can with essential nutrients that can not be made with their enzymes.not be made with their enzymes.

Minerals and vitaminsMinerals and vitamins

Ingestion – Where is the animal in Ingestion – Where is the animal in the Food Webthe Food Web

Herbivores – eat only plants, Herbivores – eat only plants, mouthparts adapted to their food mouthparts adapted to their food source, coevolution with bacteria and source, coevolution with bacteria and protists to digest cellulose, longer protists to digest cellulose, longer small intestinesmall intestine

Carnivores – eat only animals, Carnivores – eat only animals, mouthparts, shorter small intestinemouthparts, shorter small intestine

Omnivores – somewhere in between! Omnivores – somewhere in between!

Feeding MechanismsFeeding Mechanisms Suspension feeding – food particles Suspension feeding – food particles

removed from waterremoved from water Substrate feeding – live on the food Substrate feeding – live on the food

source e.g. leaf miners, dung beetlessource e.g. leaf miners, dung beetles Deposit feeding – earthworms take in Deposit feeding – earthworms take in

soil and remove organic materialsoil and remove organic material Fluid feeding – mosquito, leachesFluid feeding – mosquito, leaches Bulk feeding – large meals, not much Bulk feeding – large meals, not much

chewingchewing

Food ProcessingFood Processing Ingestion – Digestion – AbsorptionIngestion – Digestion – Absorption Ingestion – teeth – dentition, tongueIngestion – teeth – dentition, tongue Digestion physical or chemical – Digestion physical or chemical –

hydrolytic enzymeshydrolytic enzymes Absorption – once food is broken Absorption – once food is broken

down, the materials must be down, the materials must be absorbed and transported absorbed and transported throughout the body.throughout the body.

Intracellular DigestionIntracellular Digestion Paramecium exampleParamecium example paramecium

Gastrovascular CavityGastrovascular Cavity Hydra and planarianHydra and planarian

Alimentary CanalAlimentary Canal Mouth Mouth EsophagusEsophagusStomachStomachSmall Small

IntestineIntestineLarge IntestineLarge IntestineRectumRectumAnusAnus Mouth digestion of starch via amylaseMouth digestion of starch via amylase Stomach – pepsin begins digestion of Stomach – pepsin begins digestion of

protein into smaller polypeptidesprotein into smaller polypeptides Small intestine – breakdown and absorb Small intestine – breakdown and absorb

nutrientsnutrients Large intestine – reabsorption of water and Large intestine – reabsorption of water and

mineralsminerals

Gastrointestinal SystemGastrointestinal System Function-physical and Function-physical and

chemical breakdown of chemical breakdown of foodfood

Includes alimentary Includes alimentary canal and accessory canal and accessory organsorgans

Accessory organs: Accessory organs: Salivary glands, tongue, Salivary glands, tongue, teeth, liver, gallbladder, teeth, liver, gallbladder, and pancreasand pancreas

Alimentary canalAlimentary canal Mouth- physical Mouth- physical

and chemical and chemical breakdown.breakdown.

Mastication-the act Mastication-the act of chewingof chewing

Saliva contains Saliva contains enzyme amylase to enzyme amylase to break down break down carbohydratescarbohydrates

Pharynx- contains Pharynx- contains opening to trachea as opening to trachea as well. Epiglottis covers well. Epiglottis covers opening of trachea.opening of trachea.

Esophagus-muscular Esophagus-muscular tube dorsal to tube dorsal to tracheatrachea

Relies on a rhythmic Relies on a rhythmic wave-like motion wave-like motion called peristalsiscalled peristalsis

Esophagus- transverse view

Sphincter-a circular Sphincter-a circular muscle that muscle that constricts a passage constricts a passage or closes a natural or closes a natural orifice (opening)orifice (opening)

Cardiac sphincterCardiac sphincter Pyloric sphincterPyloric sphincter Food sits in stomach Food sits in stomach

for 1-4 hours. for 1-4 hours. Gastric juices Gastric juices contain hydrochloric contain hydrochloric acid- activates acid- activates pepsin, kills pepsin, kills bacteria.bacteria.

Small intestine: not Small intestine: not so small! 20ft x 1’’so small! 20ft x 1’’

Duodenum- 1Duodenum- 1stst 10 10 inches. Bile and inches. Bile and pancreatic juice pancreatic juice enter hereenter here

Jejunum- next 8 ft.Jejunum- next 8 ft. Ileum- final 12 ft. Ileum- final 12 ft.

When food leaves When food leaves small intestine, small intestine, digestion is digestion is completecomplete

Small intestine has Small intestine has lots of enzymes: lots of enzymes: peptidases peptidases

maltase, sucrase, maltase, sucrase, lactase, amylase.lactase, amylase.

Lipase Lipase BileBile

Digested food is Digested food is absorbed into the absorbed into the bloodstream. bloodstream.

Large intestine- 5 ft Large intestine- 5 ft x 2’’. Separated x 2’’. Separated from small intestine from small intestine by ileocecal valveby ileocecal valve

Final absorption of Final absorption of water, storage of water, storage of indigestible indigestible material, absorption material, absorption of vitamins B and K of vitamins B and K by bacteria.by bacteria.

Colon connects to Colon connects to rectum- anal canal rectum- anal canal opens to the anus opens to the anus (final opening). (final opening). Fecal material is Fecal material is expelled.expelled.

But Wait! What about the accessory But Wait! What about the accessory organs: Liver, gall bladder and organs: Liver, gall bladder and pancreaspancreas Liver- largest gland Liver- largest gland

in your bodyin your body Secretes bile- Secretes bile-

emulsifies fat, emulsifies fat, makes them water makes them water soluble.soluble.

Stores glucose in Stores glucose in the form of glycogenthe form of glycogen

Makes clotting Makes clotting proteinsproteins

Detoxifies bloodDetoxifies blood

Gall bladder- stores Gall bladder- stores and concentrates and concentrates bilebile

Pancreas- produces Pancreas- produces insulin, pancreatic insulin, pancreatic juices amylase and juices amylase and lipase. Insulin lipase. Insulin regulates the regulates the uptake of glucose uptake of glucose by the cells by the cells

QuestionsQuestions

1.1. What parts of the model accurately What parts of the model accurately portrayed the action of the portrayed the action of the digestive system?digestive system?

2.2. How could we improve this model of How could we improve this model of digestion?digestion?

3.3. What organs are play a part in What organs are play a part in digestion, but are not present in the digestion, but are not present in the alimentary canal?alimentary canal?

Stomach exampleStomach example Physical churningPhysical churning Acid released by cells in response to the Acid released by cells in response to the

hormone Gastrin that is released when a hormone Gastrin that is released when a person eats.person eats.

Pepsinogin is also released by separate cells Pepsinogin is also released by separate cells – the acid in the stomach changes the – the acid in the stomach changes the shape of pepsinogin to its active form shape of pepsinogin to its active form pepsin. Pepsin stimulates more acid – pepsin. Pepsin stimulates more acid – positive feedback.positive feedback.

Acid and Pepsinogin do not mix until they Acid and Pepsinogin do not mix until they reach the lumen of the stomach or else it reach the lumen of the stomach or else it would digest the stomach. Stomach lumen would digest the stomach. Stomach lumen is coated with mucus to protect it.is coated with mucus to protect it.

Stomach continuedStomach continued The food + water + acid and The food + water + acid and

enzymes = acid chyme which passes enzymes = acid chyme which passes to the the duodenum of the small to the the duodenum of the small intestine.intestine.

Ulcers – most caused by a bacteria Ulcers – most caused by a bacteria called called Helliobacter pyloriHelliobacter pylori treated with treated with antibiotics antibiotics

Small IntestineSmall Intestine Duodenum – beginning of small Duodenum – beginning of small

intestine the chyme is acidic, intestine the chyme is acidic, digestive enzymes are secreted by digestive enzymes are secreted by the pancreas, liver, and gall bladder the pancreas, liver, and gall bladder (bile), but are active in a neutral pH. (bile), but are active in a neutral pH. Cells add Sodium bicarbonate to Cells add Sodium bicarbonate to neutralize the acid chyme.neutralize the acid chyme.

Jejunum – villi and micro villi absorb Jejunum – villi and micro villi absorb nutrientsnutrients

The End of the LineThe End of the Line 7 liters of liquid are passed through the 7 liters of liquid are passed through the

stomach and small intestine each day.stomach and small intestine each day. Much is reabsorbed by microvilli into Much is reabsorbed by microvilli into

lacreal cells in the small intestine.lacreal cells in the small intestine. More water and minerals are More water and minerals are

reabsorbed by the large intestine.reabsorbed by the large intestine. Food digestion takes 12-24 hours. Food digestion takes 12-24 hours.

Longer = less water, Shorter = more Longer = less water, Shorter = more waterwater

And thenAnd then More cellulose in the diet = faster More cellulose in the diet = faster

movement.movement. E. coli E. coli lives in the large intestine on lives in the large intestine on

undigested food. The bacteria undigested food. The bacteria produce vitamins and some strains produce vitamins and some strains help to fight off infections by out-help to fight off infections by out-competing the bad guys.competing the bad guys.

Interesting AdaptationsInteresting Adaptations Herbivores have a longer cecum – Herbivores have a longer cecum –

usually with symbiotic prokaryotes usually with symbiotic prokaryotes and protists that digest cellulose.and protists that digest cellulose.

Rabbits have their symbionts living in Rabbits have their symbionts living in their large intestine instead. They eat their large intestine instead. They eat the digested food (poo) from the first the digested food (poo) from the first time around and the typical pellets time around and the typical pellets you see are food that has been you see are food that has been through twice.through twice.

RuminentsRuminents Deer, cows, horsesDeer, cows, horses They have a four chambered alimentary They have a four chambered alimentary

canal. They end up “chewing the cud” canal. They end up “chewing the cud” cud is made up of food after it has been cud is made up of food after it has been metabolized by the protists and bacteria.metabolized by the protists and bacteria.

It passes through the digestive system It passes through the digestive system again.again.

Ruminents actually get most of their Ruminents actually get most of their nutrition from the digestion of the nutrition from the digestion of the microorganisms living inside of them!microorganisms living inside of them!