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External Anatomy
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Label all 6 fins:
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External Anatomy
Operculum
Nostril or Nare
Eye
Scales
Mouth
Lateral Line
Study the external anatomy. Locate the nostrils.
Feel the fish’s skin. Use the magnifying glass to view the scales and
how they are arranged. Feel their texture.
Feel the bony rays that support the fins. How many rays are on the
anal fin? ____
External Anatomy
Teeth
Teeth are found along
the upper and lower
jaws. They grasp and
hold onto prey.
Dar
Open the trout’s mouth and feel the teeth along the gum margins. Open it as wide
as you can without breaking the jaw.
Feel the tongue. What are on it? ______
Find the gill rakers from the inside of the mouth that lead to the gills.
Gills
Gill filaments
Gill arch
Dar
Place the fish on its side and look at the operculum (the bony plates
which protect the gills).
Lift the operculum to see the gills.
Carefully cut the operculum away from its base, exposing the gills.
Compare and contrast the trout’s gills with a mammal’s lungs below:
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Internal Anatomy
Swim bladder
Dar
Heart
Liver
Gall bladder
Spleen
Kidney
Carefully cut a flap to expose the internal organs using a scalpel or scissors.
Cut away the flap of skin and look for fat deposits which are found around the
stomach.
• Put the fish on its back to find the kidneys
located under the backbone. They are thin
and dark in color and run the length of the
body’s cavity.
• Look for the swim bladder. It is made of very
thin tissue and is located in the upper body
cavity below the kidneys. It may be hard to
find.
• Look for the liver at the top of the abdominal
cavity. Can you find the gall bladder where
bile is stored?
Digestion
Stomach
Intestine
Pyloric caeca
Fat
The path of digestion for a trout is: mouth, esophagus, cardiac stomach, pyloric
stomach, intestines, anal opening.
Why might a fish need 2 stomachs? __________________________________
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What do you think the purpose of a fish’s intestines are?__________________
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Dar
Heart and Gills
Gills
Dar
Heart
Compare the location of the heart to the gills. ___________
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Why is this important? (What is happening in the gills that
happens in our lungs?) ______________________________
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