5 th Grade
Frog Dissection
Updated 3/31/15
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Fish, preserved
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Dissecting equipment
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Pan
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Paper towels
 Scalpel
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Hand lens
A.
External Anatomy: a.
Observe the color of the skin on the front and bottom of the frog. b.
Observe the size of the mouth compared to the size of the head. c.
Look closely at the two nostrils. d.
Observe the eyes and eyelids. Each eye is protected by three eyelids. e.
Behind the eyes are the tympanums, or the “ears”. f.
Place the frog on its back to observe its legs. Gently bend the legs.
B.
Internal Anatomy-Oral Cavity: a.
CAUTION: Always cut away from yourself and others. Rotate the dissection pan, if necessary, for better control while dissecting. Place the frog onto its left side.
Feel along the lower jaw, called the mandible, to locate the hinge joint of the jaw.
Insert a dissecting pin behind the joint. b.
Carefully put scissors into the mouth, aligning them from the corner of the mouth to the dissection pin. Cut through the hinge joint of the jaw. c.
Turn the frog onto its right side and repeat. Pry the mouth open exposing the back of the throat. d.
The tongue is the most prominent feature within the mouth. Observe the surface and locate the attachment in the mouth. e.
Note the teeth on the jaw. They are not used to chew prey but instead they help to hold insects within the mouth cavity. f.
There is a set of internal nares between the sets of teeth. g.
There are also eye bulges lateral to the vomerine teeth. h.
Take note if your specimen has one or two set of openings by the jaw note. Males have two pairs of openings. Females lack the openings.
C.
Muscles and Skin Regions: a.
Use dissection pins to pin down the frog on its back. b.
CAUTION: Always cut away from yourself and others. Rotate the dissection pan, if necessary, for better control while dissecting.

5 th Grade Updated 3/31/15
Frog Dissection c.
Use dissection scissors to cut a small hole at the bottom of the frog. Slip the scissors just under the skin. d.
Lift the skin away from the underlying muscle layer and make an incision from the end of the trunk to the edge of the lower jaw. The cut should be off center. e.
Cut the “V” of the hind legs, and around the head by the forelegs. Just cut the skin. f.
Pin open the flaps of skin. Observe the skin and veins. g.
Take note of the muscles. h.
Use scissors to cut from thigh to foot on each leg. i.
Use scissors to cut from the trunk of the frog to the top, through the muscles. Be careful to not cut through the organs. j.
Use a dissecting needle to detach the ventral abdominal vein from the underside of the muscle wall. k.
Pin the muscle on top of the skin. l.
The pleural membranes line the internal cavity and are attached to the inside of the muscle layer. The pericardial membrane surrounds the heart. Feel both with gloved hands.
D.
Digestive System: a.
Locate the large brownish liver. It is the largest solid organ in the frog. It has 3 lobes. b.
Behind the liver is the gallbladder (dark green and round). c.
Use a scalpel to carefully remove the lobes of the liver. Place the liver on the dissecting tray. d.
Locate the stomach. Move it to the side to locate the pancreas. e.
Identify the intestines as well. f.
Use scissors to cut the stomach lengthwise. Note any contents found inside.
E.
Circulatory System: a.
Locate the heart. Do not confuse the lungs with the heart. Frogs have a 3 chambered heart-2 atrium and 1 ventricle. b.
The spleen is located under the intestines. Locate it.
F.
Respiratory System: a.
Locate the pair of smallish lungs on either side of the heart. Trace one of the brachial tubes to the larynx and note where it passes into the mouth. You may need to remove the heart to do this. If you remove the heart, place it on the tray.
G.
Urogenital System: a.
Use scissors to remove both the small and large intestine. Place them on the tray.

5 th Grade Updated 3/31/15
Frog Dissection b.
Locate the large bean shaped kidneys along the dorsal body wall. c.
If the specimen is male, the testes will look like small, tan, bean-shapped objects by the kidneys. d.
If the specimen is female, you could have dark gray mature eggs, or tan ovaries by the kidneys.
H.
Nervous System: a.
Turn the frog over. Use a scalpel to cut on either side of the backbone. Lift the skin and muscles off the backbone. b.
Use a scalpel to remove the skin from the top and back of the skull. Be careful to not damage the soft brain under the skull. Make small snips over the top crestof the skull to the arch above the eyes. Cut around the skull back to the original starting point. Gently life the cranium with forceps. c.
Observe the brain.
I.
Observations & Reflections: a.
Typed or hand written b.
Full school heading c.
Discuss your dissection experience. What did you enjoy? What did you observe?
What did you dislike about dissection? d.
1-2 paragraphs long. e.
DUE: Wednesday, April 15, 2015.