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The Digestive System. The mysterious process uncovered!. The Beginning. Oral cavity : Both physical and chemical digestion takes place in the mouth. Saliva: secreted to moisten food, protect the mouth from abrasions buffer against acids in food, kill some forms of bacteria

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The Digestive System


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the digestive system

The Digestive System

The mysterious process uncovered!

the beginning
The Beginning
  • Oral cavity:
    • Both physical and chemical digestion takes place in the mouth.
  • Saliva:
    • secreted to moisten food,
    • protect the mouth from abrasions
    • buffer against acids in food, kill some forms of bacteria
    • begin carbohydrate digestion with the enzyme SALIVARY AMYLASE.
  • Tongue:
    • is used for taste, manipulates food while chewing and
    • prepares food for swallowing by forming it into a ball called a bolus.
down the hatchet or pharynx and esophagus
Down the hatchet (or Pharynx and esophagus)!
  • Pharynx
    • Commonly called the throat.
    • Intersection of the glottis and opening to the esophagus is found here.
    • Epiglottisis a flap that closes the glottis when the act of swallowing occurs.
  • Esophagus
    • Connects the pharynx and the stomach.
    • Peristalsis, wave-like contractions of the smooth muscles push food down toward the stomach.
    • Connects with the stomach at the CARDIAC SPHINCTER.
into the stomach
Into The Stomach
  • J shaped expandable organ located on the left side of the abdominal cavity.
  • Stores up to 2 liters of food while mixing and digesting it.
  • The epithelial cells secrete GASTRIC JUICES and HCl making the pH around 2.
  • PEPSINOGEN : an enzyme used to partially hydrolyze protein; pepsinogen reacts with HCL to form pepsin.
  • The hormone GASTRIN is secreted by the stomach cells to regulate the production of gastric juices.
  • Fat Digestion:Bile emulsifies fat. This creates a larger surface area for the enzyme lipase to digest it.
  • Carbohydrate Digestion: Disaccharide digestion is under the control of the enzymes maltase, lactase, sucrase, all of which are mainly found in saliva.
  • The stomach is closed at its posterior end by the PYLORIC SPHINCTER
small intestine and villi
Small Intestine and Villi
  • Most hydrolysis of macromolecules occur here
  • It is more than 6 meters in length with smaller diameter than large intestine.
  • It is divided into 3 sections: duodenum, jejunum, and ileum
  • Pancreas, Liver, and Gall Bladder:
    • accessory organs, add digestive enzymes, juices and hormones into the small intestine.
  • The hormone Cholecystokinin (CCK) is released from the intestinal cells causing the gall bladder to release bile. It also causes the pancreas to release its digestive enzymes.
absorption
Absorption
  • Absorption and distribution of nutrients:
    • Small intestine is lined with small finger-like projections called Villi
    • Each villus contains a net of capillaries and a large lymph vessel called a lacteal
    • The nutrients except fat are absorbed into the capillaries, while the fat enters the lacteal.
    • All the contents of the blood enter the liver via the Hepatic portal vein.
    • The liver regulates the contents of the blood.
large intestine
Large Intestine
  • Colon is connected to the small intestine at a T junction called the cecum.
    • The appendix is found attached to the end of the cecum.
  • The main function of the colon is to reabsorb water from the small intestinal material.
  • The bacteria Escherichia coli live in this area of the body. They produce odor, and Vitamin K.
  • Waste is excreted through the rectum and out through the anus
now who s hungry
Now, who’s hungry?
  • Digestion Transit Times:
    • Mouth:
      • one minute
    • Esophagus:
      • two to 3 seconds
    • Stomach:
      • 2-4 hours
    • Small Intestine:
      • 1-4 hours
    • Large Intestine:
      • 10 hours to several days!
  • Digestion is now complete, time to eat again!
  • Review rubric for digestion t-shirt and digestion creative writing assessment!