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The Digestive System. pg. 324 - 338. Function. The main function of the digestive system is to break down macromolecules into substances the body can use. Digestion. Food provides (most of) the nutrients we need to survive Food is processed in 4 stages: Ingestion Digestion Absorption

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The digestive system

The Digestive System

pg. 324 - 338


Function
Function

  • The main function of the digestive system is to break down macromolecules into substances the body can use


Digestion
Digestion

  • Food provides (most of) the nutrients we need to survive

  • Food is processed in 4 stages:

    • Ingestion

    • Digestion

    • Absorption

    • Elimination





The digestive tract is a tube that runs from the mouth to the anus. Food passes through the tract and its related organs.

The accessory organs are ones that assist in the process of digestion, food does not travel through them.



In the mouth
In the mouth...

  • Digestion begins in the mouth

    • Mechanical destruction of food

      • specialized, omnivorous teeth

      • why do we chew food?

    • Enzymatic breakdown of food

      • saliva enzymes break chemical bonds (remember the soda cracker?)






Through the pharynx and esophagus
Through the pharynx and esophagus...

  • Peristalsis occurs in the esophagus and small and large intestines to move food

    Peristalsis – involuntary smooth musclecontractions that force contents onward


To the stomach
To the stomach...

  • The human stomach contains complex gastric juices that continue the breakdown of food

  • These juices contain...

    • mucus

    • hydrochloric acid

    • enzymes


Just beyond the stomach
*Just beyond the stomach...

  • The “chyme” is treated by accessory organs


Accessory organs
*Accessory organs

  • Liver

    • Produces bile

  • Gallbladder

    • adds bile to digest fats

  • Pancreas

    • adds additional digestive enzymes

  • *Kidneys & bladder

    • remove waste from circulating blood to make urine


Into the small intestine
Into the small intestine...

  • In the small intestine (~6m long), macromolecules are digested into monomers and absorbed into the blood stream

  • Villi & microvillimaximize the absorptivesurface area

  • Absorption into blood


The l arge intestine home stretch
The large intestine home-stretch...

  • Unabsorbed materials enter the large intestine (~1.5m long)

  • Primary roles:

    • House helpful bacteria

    • Absorb water

  • 10 trillion bacterial cells convert undigestible nutrients into things we can use


Finally the rectum anus
Finally, the rectum & anus!

  • Rectum

    • holding area for feces

    • absorbs a little water

  • Anus

    • sphincter that releases feces


Homeostasis
Homeostasis

  • Define the following:

    • Cirrhosis

    • Gall stones

    • Ulcer

    • Colon cancer

  • For the digestive complications above, list their symptoms and treatments




Try t hese
Try these...

  • In essay format, describe the entire digestive process from eating to defecating, being as descriptive as possible

  • pg. 353, #1 – 12, 18 – 21, 44, 45 & 47


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