Transcript The Digestive System - University of Dallas

The Digestive System
The mysterious process
uncovered!
The Beginning
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Oral cavity:
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Saliva:
 Both physical and chemical digestion
takes place in the mouth.
 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.
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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)!
Pharynx
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Commonly called the throat.
Intersection of the glottis and
opening to the esophagus is
found here.
Epiglottis is a flap that closes
the glottis when the act of
swallowing occurs.
Esophagus
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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
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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
Stomach Photo
Small Intestine and Villi
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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,
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Pancreas, Liver, and Gall Bladder:
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and ileum
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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 and distribution of nutrients:
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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
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The liver regulates the contents of the blood.
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Hepatic portal vein.
Pancreas and Villi
Large Intestine
Colon is connected to the small intestine at a T
junction called the cecum.
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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?
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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!
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Digestion is now complete, time to eat again!
Review rubric for digestion t-shirt and digestion creative
writing assessment!