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Digestive System II. SBI3U Ms. De Sousa. How Animals Obtain their food. Autotrophs : Take energy from the environment in the form of sunlight or inorganic chemicals Use the energy to create energy-rich molecules. Examples : plants and algae. How Animals Obtain their Food.

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Digestive System II


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digestive system ii

Digestive System II

SBI3U

Ms. De Sousa

how animals obtain their food
How AnimalsObtaintheirfood

Autotrophs:

  • Take energy from the environment in the form of sunlight or inorganicchemicals
  • Use the energy to create energy-rich molecules.
  • Examples: plants and algae
how animals obtain their food1
How AnimalsObtaintheir Food

Heterotrophs:

  • Take in autotrophsas food.
  • Depend on autotrophs for the energy and raw materials they need
  • Heterotrophs obtain energy by breaking down organic molecules obtained from the autotrophs
  • Examples: all animals, mostfungi, bacteria and protozoa.
animals i e heterotophs
Animals (i.e. heterotophs)
  • Have adaptedmechanisms to search, obtain and take in theirfood.
  • Animalsobtainfoodfromeither of the following 4 mechanisms.
feeding mechanisms
FeedingMechanisms

1) FilterFeeding:

  • Use a filter basket to obtainorganismssuspended in the water.
  • Siphon water intoitsmouth and filtersit to obtainitsfood.

Examples: Tube worms, clams, whales

feeding mechanisms1
FeedingMechanisms

2) SubstrateFeeding:

  • Live within or on the food source and eattheirwaythroughit.
  • Examples : Earthworms, caterpillars
feeding mechanisms2
FeedingMechanisms

4) Bulk Feeders:

  • Most vertebrates (includinghumans).
  • Ingest large pieces of food or swallowitwhole.
  • Differentanimalsmay use tentacles, pincers and claws to eat.
feeding mechanisms3
FeedingMechanisms

3) Fluid Feeders:

  • Suck or lickfluidsform plants or animals.
  • Theirmouth parts are adapted to piercethrough skin or leaf tissue.
  • Examples: spidders, bees, butterflies.
digestive tract
Digestive Tract
  • In order for the cells to obtainnutrients, the digestive system needs to break them down intosmall, soluble units.
  • The smallunits of nutrientsdiffuse intocell membranes and into the circulatory system.
alimentary canal
Alimentary Canal
  • Most animals have a digestive tract alsoknown as « Alimentary Canal »
  • Alimentary Canal: tube wherefood in processed, beginningat the mouth and endingat the anus.
  • There are variousorgansalong the alimentary canal thatprocess the food.
alimentary canal1
Alimentary Canal

Pouchlike structure thatsoftens and stores food

Example: Earthworm

Churns and grinds the food

slide14

All organs in the digestive system play a vital role in the process of digestion. Eachorganisresponsible for eitherbreaking down the food, abosrbingit or deliveringit to other areas.

similarities and differences
Similarities and Differences
  • The function of the alimentary canal is the same for all animals.
  • The lengthdiffersaccording to feeding habits.
  • Herbivores and Omnivores have longer digestive tracts thanCarnivores.
stages of digestion
Stages of Digestion
  • No matter the feedingmechanisms all animalsundergoe the same 4 stages of digestion.

a) Ingestion

b) Digestion

c) Absorption

d) Elimination

stages of digestion1
Stages of Digestion
  • Ingestion:Taking in the food
  • Digestion: Breakdown of foodintosmallmolecules
  • Absorption: diffusion of smallmoleculesinto the circulatory system
  • Elimination: removal of undigestedsolidwastefrom the body.
main types of digestion
Main Types of Digestion:

Mechanical: physical breakdown of macronutrients (i.e. chewing, churning)

Chemical: chemical breakdown of nutrientsintosmallermolecules by hydrolysisand enzymatic action.

10 2 the human digestive system
10.2 The Human Digestive System

The digestive tract has numerousorganswithspecificfunctions. Eachorganhelpsto breakdown food.

diagram of digestive system
DIAGRAM OF DIGESTIVE SYSTEM:

Mouth

Esophagus

Liver

Stomach

Pancreas

Gallbladder

Small Intestine

Large Intestine

Rectum

Appendix

Anus

slide22

STEP 1: INGESTION

Mouth

Mechanical digestion: Teethbreakdown the foodintosmallpieces

Chemical digestion:

Amylase (enzyme) breaks down the bonds in carbohydrates.

slide23

Salivaissecretedfrom 3 salivaryglands.

  • The secretion of saliva istriggeredbeforeyou have food in yourmouth.
role of saliva chemical digestion
Role of Saliva (Chemical Digestion)
  • Amylase (enzyme) breaks down carbohydratesintosimplersugars.
  • Dissolves water soluble foodparticles
  • Stimulates taste buds.
  • Lubricates the foodsoitcanbeswallowed.
slide25

When the mouth has created a bolus of food, the tongue pushes it back into the back of the throat.

  • Epiglottis – flap covers trachea so food doesn’t get in
  • Food stretches walls of esophagus and moves downward through waves of contractions called peristalsis
esophagus
Esophagus
  • Glands in the liningproducemucuswhichkeeps the tube moist and facilitatesmovement of food.
  • The muscles in the esophaguscontractinvoluntarily to push the bolus of foodinto the stomach.

Video

esophagus1
Esophagus
  • When the bolus of food has reached the bottom of the esophagus the EsophagealSphincter opens.
  • Whileswallowing, the muscles relax, opening the sphincter and allowing the food to enter the stomach.
acid reflux

The esophageal sphincter usuallyremainsclosed to preventacidicjuicesfromflowing up into the esophagus.

Acid Reflux

Video

slide30

STEP 2: DIGESTION

Stomach

  • Muscular, J-shapedorgan
  • Leftside of the abdominal cavitybelow the diaphragm
  • Performsbothchemical and mechanical digestion
stomach
Stomach
  • The walls of the stomach are foldedsothatitcanexpandafter a meal.
  • The glands on the stomachwall release « gastricjuice » whichconsist of HCl, salts, enzymes, water and mucus. (chemical digestion)
  • The walliscovered in a mucus coatwhichprotectsitfrom the acidreleasedfrom the gastricjuices.
stomach1
Stomach

Pepsinis the enzyme released.

Pepsinremains inactive (pepsinogen) untilHClissecretedform the glands.

Once activated, pepsinhydrolyzesproteins.

stomach2
Stomach
  • The HCl breaks down food and destroys foreignbacteria in the food.
  • Stomachcontracts and relaxes to churn the food.
  • The churninghelpsto break up the foodand mix the gastricjuices.
  • Food + Gastricjuices = Chyme
pyloric sphincter
Pyloric Sphincter

The Pyloric Sphincter opens to move the chyme into the small intestine.

slide35

STEP 2: DIGESTION Cont’d

Small Intestine

  • Furtherbreaks down and abosrbsnutrients.
  • Composed of three main components:

1) Duodenum

2) Jejunum

3) Illeum

duoedenum
Duoedenum
  • Receivessecretions(enzymes) fromthe gallbladder and pancreasto further breakdown nutrients.
  • The intestinal glands also release trypsin and chymotrypsin (enzymes) to breakdown carbohydrates and proteins.
  • Breaks down proteins, fats and carbohydrates.
jejunum
Jejunum
  • 2.5 m long.
  • Contains more foldsthan the duodenum.
  • Breaksdown the remainingproteins and carbohydratessothatitcanbeabsorbed.
villi and microvilli
Villi and Microvilli
  • Small intestine iscoveredby tinyfinger-likeprojections called« Villi »
  • The villiincreases the surface area for absorption of nutrientsinto the bloodstream.
  • There is a capillary network within the villi. The nutrients diffuse from the small intestine into the villiwherebyitthen diffuses into the capillary network.
illeum
Illeum
  • 3 m long.
  • Has fewervillithan the dueodenum and jejunum.
  • Absorbsnutrientsthrough the villiand pushesundigestedmaterialinto the large intestine.
slide41

STEP 3: ABSORPTION

Small Intestine and Large intestine

The villi and microvilliincrease surface area for absorption. The nutrients diffuse into the capillarieswithin the villi.

slide42

STEP 3: ABSORPTION

Small Intestine and Large intestine

  • Large intestine (colon) is 1.5 m in length
  • Reasborbs90% of water and electrolytesback into the blood.
  • Bacterialive hereproducingvitamin K /B and break down undigestedmatter.
  • Anyundigestedmaterialthatremainsiscalledfeces.
  • Fecalmatterisstoredhere for eliminationthrough the rectum.
slide43

STEP 4: ELIMINATION

Rectum

Main component of feces:

  • Cellulose- makes up plant cell walls, cannot be digested by humans
  • Living and dead bacteria
  • Water
  • Toxic wastes are removed
  • People who don’t eat enough cellulose (plant material and fibre) have fewer bowel movements and are at risk of colon cancer.
pancreas
Pancreas
  • Secretes about 1 L of pancreaticfluidinto the duoedenumeachday.
  • PancreaticFluid:

1) Lipase (enzyme) – chemically digest lipids

2) Bicarbonate– alterspH of chyme sothatenzymescanbeactivated. (pH 1 to pH 8)

liver
Liver
  • Largestinternalorganin the human body.
  • Releases bile (greenish-yellowfluid made up of bile pigments and salts)
  • Bile is sent to the gallbladderwhereitistemporarilystored.
slide47
Bile
  • Fats are insoluble in water and remainsuspended in the chyme.
  • The bile salts break up the fat dropletssotheycan disperse through the chyme.
  • The enzymes break the dropletsapart.

Video

http://www.youtube.com/watch?v=Z7xKYNz9AS0

digestive enzymes

Enzymes – proteinsthat speed up chemicalreactions

Digestive Enzymes

Induced Fit Model

The substrate and enzyme have complementaryshapes. Thusmakingthem fit perfectlyinto one another.

Therefore, the enzyme ishighlyspecific to itssubstrate.