Lab: Frog Dissection
|Purpose: Study the external and
internal anatomy of the frog.
Background info: As members of the class Amphibia, frogs may live some of their adult lives on land, but they must return to water to reproduce. Eggs are laid and fertilized in water.
|3) Use the diagram below to locate and identify
the external features of the head. Find the mouth, external nares (nostrils),
tympani (eardrums), and eyes.
_ external nares
|4) Turn the frog on its back and pin down the
legs. Cut the hinges of the mouth and open it wide. Use the diagram below
to locate and identify the structures inside the mouth: the vomerine and
maxillary teeth, the internal nares, the tongue, and the esophagus (food
_ vomerine and maxillary teeth
_ internal nares
|5) Insert the point of your scissors through
the skin just above the anal opening and make an incision extending to the
lower jaw. Make 2 horizontal incisions, open the skin flaps, and pin the
skin flaps flat.
|6) Make the same incisions as step 5 to cut
through the muscles and breast bone. Pin the muscle flaps just like you
did with the skin. NOTE: If your frog is a female, the abdominal cavity
may be filled with dark-colored eggs. If so, remove the eggs so you can
see the organs underlying them.
|7) Observe the following organs
_ Liver - large, brownish organ covering most of the body cavity
_ Heart - small triangular organ between front legs and above liver
Layer 2: Lift liver with forceps to see
_ Gall Bladder - small greenish sac under liver
_ Stomach - large, firm sac on left side
_ Small Intestine - long, folded tube smaller than and above stomach
|8) Carefully remove the liver, heart, and gall
bladder. Then observe the following organs
_ Lungs - small, reddish organs on either side of the heart
_ Pancreas - thin, yellowish ribbon between stomach and small intestine. Lift stomach to view.
|9) Carefully remove the stomach, small intestines,
and pancreas. Then observe the urinary and reproductive system.
_ Testes - tan, bean shaped organs
_ Ovaries - dark organ which may fill most of the body cavity
|10) Dispose of your frog according to the directions
from your teacher.
11) Clean all equipment and your work area. Wash your hands.