The Digestive System

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The Digestive System

• Its a Wild Ride!

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The Functions of the Digestive System

• 1.     Ingests food! (Duh!)
• 2.     Digests food while it is being forced
• along digestive tract.
• 3.     Absorbs digested food into cells of
• body
• 4.     Eliminates undigested materials
• from body

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Some important terms

• Mechanical digestion-the physical process of
  breaking food into smaller pieces
• Chemical digestion-the chemical process of
  structurally changing the food molecules with
  enzymes.

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All Aboard-First Stop-The Mouth!

•         Teeth-adapted for tearing and
  grinding food
•         Tongue-manipulates food
•         Saliva-1) Lubricates food
• 2) Contains amylase which
• starts the breakdown of
  starch
• YOU PRODUCE 1-1.5 L OF SALIVA PER DAY!!!!!!

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The Mouth!
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Website fun

• http//www.animated-teeth.com/bad_breath/t1_halito
  sis.htm Do you have bad breath?
• http//www.animated-teeth.com/ - information
  regarding anything from bad breath to cancer
  sores
• http//www.hivdent.org/_peag/peagindex.htm
  Dental Patient Information

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Second Stop-Throat and Esophagus!

•         The mouth forms the chewed food into a
  ball and moves it to the throat for swallowing.
•         Swallowing forces the food into the
  esophagus.
•         The esophagus is like a busy expressway
  to the stomach! It has waves of muscle
  contractions that push the food down the body
  into the stomach!
• THIS HAPPENS IN 5-8 SECONDS!

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The trip down the esophagus
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Throat and Esophagus

• Peristalsis-the muscle contractions that move the
  food down into the stomach
• Epiglottis-covers the opening to the windpipe

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Throat and Esophagus
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Third Stop-The Almighty Stomach!

• Stomach-a muscular, pouch-like enlargement of
  the digestive tract
• Muscular Churning- three layers of muscle
  contract and mix food in the stomach (mechanical
  digestion) 

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Note the muscle in the stomach!
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Protection in the stomach

• Gastric juice-secreted by the stomach lining and
  contains hydrochloric acid and enzyme pepsin.
• Pepsin only works in an acidic environment.
  (stomach pH is 2!)
• Protective mucus prevents stomach from digesting
  itself!

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The Almighty Stomach!
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Website fun

• http//www.gerd.com/intro/noframe/gena_shk.htm
  acid reflux simulation
• http//camel2.conncoll.edu/academics/zoology/cours
  es/zoo202/Digestive/stomach.html digestion
  process of pizza

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Fourth Stop-The Small Intestine-Small, but
Mighty!

• Small intestine-muscular tube about 6 m
• long
• That isnt small! It is small in diameter, not
  length!
• Muscle contractions further breakdown the food
  mechanically
• Duodenum-section of the SI that secretes enzymes
  to digest food
• (SI is separated from stomach by pyloric
  sphincter)

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Small Intestine
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Helpers Along the Route-Pancreas!

• Pancreas-soft, flattened gland that secretes
  enzymes and hormones
• Pancreatic juice is alkaline (pHgt7) to neutralize
  acidic food and stops pepsin!

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Pancreas
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Website fun

• http//camel2.conncoll.edu/academics/zoology/cours
  es/zoo202/Digestive/pancreas.html - pancreas
  tutorial

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More Helpers!-Liver and Gall Bladder

• Liver-Produces bile
•      
• Bile-breaks down fats
•    
• Bile is stored in the gall bladder and then
  passes into the SI

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Liver Liver, liver alone!(What movie is that
from?)
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Absorption of Food

• Liquid food stays in your stomach for 3-5 hours
•         Food moves through SI and passes over
  villi
•         Villi-fingerlike projections that absorb
  food
•         Villi increase surface area of SI
•         Villi have blood vessels and lymph
  ducts (linking immune and circulatory
  system!)

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Villi
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The Final Portal-The Large Intestine!

• Undigested material moves into LI
• LI-muscular tube, also called the colon
• LI-1.5 m long, but wider 6. 5 cm
• Appendix is an extension, but unnecessary organ!
• Water is absorbed by the LI
• Solid material is digested by bacteria in LI and
  vitamins are made
• After 18-24 hours, indigestible material is
  eliminated.
•  

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Large Intestine/Colon
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TOTAL JOURNEY TIME? 24-33 HOURS!ITS A WILD
RIDE!
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Website fun

• http//www.medtropolis.com/VBody.asp Tutorial -
  Guided Tour - Interactive
• http//www.innerbody.com/htm/body.html
  innerbody - click on picture of digestive system
  to name parts
• http//www.dpsmedia.net/flash/flashpage.asp?filepa
  thva00000025.swf human digestive system
  tutorial animation
• http//www.whitman.edu/biology/vpd/digestive.html
  - fetal pig dissection tutorial

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Website fun

• http//www.niddk.nih.gov/health/digest/digest.htm
  National Institute of Diabetes Digestive
  Kidney Diseases
• http//camel2.conncoll.edu/academics/zoology/cours
  es/zoo202/Digestive/digestive.html digestive
  system quiz game