36-2 Internal Frog Anatomy INVESTIGATION Introduction

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36-2 Internal Frog Anatomy INVESTIGATION Introduction
Internal Frog Anatomy
The frog is a complex animal with well·fonned oxygen systems. similar
to other vertebrates. In this investigation you will be dissecting the frog
to locate, identify, compare. draw, and label those internal structures.
To locate Ind identify the various
structures of the frog's major sys·
Frog (Rana pipims).
Dissecting scissors
Dissecting pan
• Relate the internal structures of
the frog to their functions.
Part A: Removing the Skin
1. Wash your frog carefully under running water to remove as much
of the preservative as possible.
2. CA lTIO~: As you cut keep scissors pointed up. or scalpel point
moying aW8) from you, to protect yourself. Place the frog in the
dissecting pan with ventral side up. With a scalpel or scissors. carefully
CUI along the mid-ventra1line
of the frog from the anus to the chin.
3. Cut the skin around the frog's wrists and ankles. From the wrists
and ankles, cut up the inside of each leg until you meet the original
4. Make a cut encircling the neck. cutting only through the skin.
5. Use forceps to peel the skin from the body. Proceed carefully. cutting
the skin from the muscles wherever it does not come off freely.
6. When it has ~n completely skinned, spread the frog out in the
dissecting pan. ventral side up.What musclef> are the largest and why.?
Plrt 8: The Respiratory
and Circulatory
,. Using a scaJpel, cut the ventral muscle waJI from the anus to the
throat. Be careful not to cut too dttply or you will damage the internal
2. Make a lateral cut from shoulder to shoulder and down either side.
Finish making a square, as in the diagram, so that the chest ar.d ab·
dominal muscles can be removed completely and the bones in the
shoulder girdle can be moved out of the way. This will expose the
coelom. If you have a female frog. the body cavity may be filled with
masses of black eggs. If this is the case, remove th.em and proceed
with the investigation .
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1Locate the following
parts on your frog. then label them on the
diagrambeJow: larynx. right and l¢ lung. right and l¢ bronchi: aOrlic
QTC~s. ~art.
1be heart is covered by a membranous sac. Remove it
with the scissors to find the right and l~ft atria. and the v~ntricl~.
Why is 1M wall of t~ ventric/~ tNcur
tMn tM wallJ of tM atria?
Part C: The Digestive System
Locate. and label on the diagram. the following structures: liver. stom·
ach. small intestine,
wrge intestine.
gall bladder.
Part D: The Urogenital System
1. Locate the cloaca. the posterior body opening. Upward from the
cIoilca are the oviducts. The oviducts in the female are quite large and
easily located. The oviducts in the male are vestigial and. therefore.
greatly reduced. but are still present.
Z. Under the oviducts are the kidneys. which lie on either side of the
spinal column. Posterior to each kidney is a tube. the ur~1tr. which
connects the kidney to the cloaca. The urinary bladder is attached to
the cloaca.
11be ovari~s. in the female. andlthe testes. in the male. are located
close to the kidneys.
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4. The for bodies an: the fingerlike projections
ovaries and testes.
What is the function
that an: anached to the
of tM fat bodies.'
5. Label all the parts of the urogenital
_ Date
system on your diagram.
and Conclusions
1. In what way is the frog similar to other vertebrates?
Z. Is the frog completely
adapted to life on land?
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1 How many chambers does the frog heart have and why is this advancement necessary for a land animal?
4. What is the function of the cloaca?
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