The Digestive System



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The GI Tract Adapted from “The Digestive System” by M. Poarch, 2002.
The entire length of the adult GI tract from mouth to anus is approximately 9-10 meters in length. Various portions of the GI tract vary in length depending on their function. The large majority of this length is located in the intestines. In this activity we will be measuring out the length of the GI tract in a scaled version to compare the lengths of each section.
Directions

Step 1 Using the ruler measure out 862 cm of string.



Step 2 Using the ruler measure out 5 cm from one end of the string and make a line or

dot on the string with a marker. 0-5 cm represents the MOUTH.



Step 3 Starting from your 5 cm mark, measure out 18 cm and make a line or dot on the

string with a marker. The 5-18 cm represents the ESOPHAGUS.



Step 4 Starting from your 18 cm mark, measure out 30 cm and make a line or dot on the string with a marker. 18-48 cm represents the STOMACH.

Step 5 Starting from your 48 cm mark, measure out 700 cm and make a line or dot on

the string with a marker. 48-700 cm represents the SMALL INTESTINE.



Step 6 Starting from your 700 cm mark, measure out 150 cm and make a line or dot on

the string with a marker. 700-850 cm represents the LARGE INTESTINE.



Step 7 Starting from your 850 cm mark, measure out 12 cm and make a line or dot on the string with a marker. 850-862 cm represents the RECTUM.

Step 8 Tape your string flat (no overlapping) on the whiteboard with the

“mouth” portion of the string at the top to demonstrate how the GI tract is arranged in the human body.



Step 9 Label the mouth, esophagus, stomach, small intestine, large intestine, and

rectum next to each portion of the string it represents below. Have Mrs. Harlow check your GI Tract.



Villi and Small Intestine Absorption

  1. Fill four beakers with equal amounts of water using the graduated cylinder.

  2. Tear off four different sections of paper towels: one section will have one towel, the second section will have two towels, the third section will have three towels, and the final section will have four towels.

  3. Fold all four towel sections so that they will fit into the beakers.

  4. Record the volume left in each of the beakers using the graduated cylinder.

  5. Answer the following questions:

    1. Which paper had the largest surface area?

    2. Which cup had the highest volume of water left?

    3. What does this activity say about the structure and function of the digestive system?

    4. How do the villi and microvilli of the small intestine aid in absorption?

  6. Observe the small intestine villi and microvilli under high power.

    1. Sketch what you see.

    2. Label the cells and recognizable organelles.

Villi and Small Intestine Absorption

  1. Fill four beakers with equal amounts of water using the graduated cylinder.

  2. Tear off four different sections of paper towels: one section will have one towel, the second section will have two towels, the third section will have three towels, and the final section will have four towels.

  3. Fold all four towel sections so that they will fit into the beakers.

  4. Record the volume left in each of the beakers using the graduated cylinder.

  5. Answer the following questions:

    1. Which paper had the largest surface area?

    2. Which cup had the highest volume of water left?

    3. What does this activity say about the structure and function of the digestive system?

    4. How do the villi and microvilli of the small intestine aid in absorption?

  6. Observe the small intestine villi and microvilli under high power.

    1. Sketch what you see.

    2. Label the cells and recognizable organelles.

Mechanical Versus Chemical Digestion

  1. Measure equal volumes of water into two different beakers.

  2. Place a sugar cube into one beaker and a sugar packet into the other beaker.

  3. Begin stirring both beakers until the sugar is completely dissolved.

  4. Describe your observations.

    1. What do you conclude must be done to food before digestion begins?

    2. Which organs/structures of the digestive system complete mechanical digestion?

    3. Which organs/structures of the digestive system complete chemical digestion?


Mechanical Versus Chemical Digestion

  1. Measure equal volumes of water into two different beakers.

  2. Place a sugar cube into one beaker and a sugar packet into the other beaker.

  3. Begin stirring both beakers until the sugar is completely dissolved.

  4. Describe your observations.

    1. What do you conclude must be done to food before digestion begins?

    2. Which organs/structures of the digestive system complete mechanical digestion?

    3. Which organs/structures of the digestive system complete chemical digestion?


CARBOHYDRATE DIGESTION

  1. Chew two unsalted crackers for two minutes WITHOUT swallowing.

  2. Describe your observations.

    1. As you were chewing the cracker, what physical changes took place?

    2. As you were chewing the cracker, what chemical changes took place?

    3. Did you notice a taste change in the cracker? If so, describe it.


CARBOHYDRATE DIGESTION

  1. Chew two unsalted crackers for two minutes WITHOUT swallowing.

  2. Describe your observations.

    1. As you were chewing the cracker, what physical changes took place?

    2. As you were chewing the cracker, what chemical changes took place?

    3. Did you notice a taste change in the cracker? If so, describe it.


TASTE BUDS

  1. Dip a cotton swab into one of the flavored solutions.

  2. Rub the cotton swab across the entire surface of the tongue until you can identify the taste as sweet, sour, salty, or bitter.

  3. Note the location where the taste is recognizable.

  4. Repeat for the other three tastes.

  5. Draw a map of the tongue showing the locations of tastes.

  6. Recent research has indicated that there is a fifth taste detected by the tongue called umami. Add umami to your tongue map and describe the flavors that umami taste buds recognize.


TASTE BUDS

  1. Dip a cotton swab into one of the flavored solutions.

  2. Rub the cotton swab across the entire surface of the tongue until you can identify the taste as sweet, sour, salty, or bitter.

  3. Note the location where the taste is recognizable.

  4. Repeat for the other three tastes.

  5. Draw a map of the tongue showing the locations of tastes.

  6. Recent research has indicated that there is a fifth taste detected by the tongue called umami. Add umami to your tongue map and describe the flavors that umami taste buds recognize.


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