13/08/2025
Dissecting Frog Procedure:
A. Safety First:
1. Wear gloves, goggles, and a lab coat or apron.
2. Handle dissection tools carefully (scissors, scalpel, pins).
3. Follow your teacher or lab supervisor’s safety guidelines.
4. Dispose of biological waste properly.
B. Preparation:
1. Place the preserved frog on a dissection tray, ventral (belly) side up.
2. Rinse the frog in water if it has excess preservative.
3. Use dissecting pins to secure each limb so the frog stays in position
C. External Observation**
1. Identify the eyes, nostrils (nares), mouth, tympanum (eardrum), and skin texture.
2. Note the webbed feet and any visible sexual differences (thumb pads in males are larger).
C. Initial Incision**
1. Locate the midline of the frog’s belly.
2. Use scissors (not a scalpel) to make a small incision in the skin just above the rear legs.
3. Cut upward toward the chest, stopping before the lower jaw.
4. Make two horizontal cuts—one near the arms and one near the legs—so you can fold the skin flaps to each side and pin them down.
D. Opening the Body Cavity**
1. Repeat the same cuts through the muscle layer underneath the skin.
2. Be careful not to damage the internal organs.
3. Pin the muscle flaps back to fully expose the internal anatomy.
E. Identifying Internal Organs**
1. Digestive system:
Esophagus, stomach, small intestine, large intestine, liver, gallbladder.
2. Circulatory system:
Heart (three chambers: two atria, one ventricle), arteries, veins.
3. Respiratory system: Lungs.
4. Excretory system: Kidneys, bladder.
5. Reproductive system: Ovaries with eggs (females), te**es (males).
F. Detailed Examination:
1. Gently lift and move organs to see structures underneath (e.g., lift the liver to view the gallbladder).
2. Use forceps for delicate handling.
3.Observe organ size, color, and texture.
G. Clean-up
1. Return all tools to the proper place.
2. Clean and sanitize the science lab.
3. Remove your lab gown and wash and sanitize your hands properly.
H. Preparation of Frog Skeleton
Steps:
1. Specimen Selection
•Choose a frog specimen with an intact body (no broken bones).
2. Skin Removal
•Place the frog on a dissecting tray, dorsal side up.
•Make an incision in the skin using scissors, then carefully peel the skin away from the muscle tissue using forceps.
3. Muscle and Organ Removal
•Remove muscle tissue by carefully cutting it away from bones without damaging the skeleton.
•Take out internal organs to expose the spine and rib cage.
•Be patient—avoid pulling forcefully, as bones are delicate.
4. Cleaning the Bones
•Place the skeleton in a shallow container.
•Add enough hydrogen peroxide (3–6%) to cover the bones.
•This whitens and cleans the bones without damaging them.
•Leave for 12–24 hours (check periodically).
•Alternatively, boil the bones gently in water for 20–30 minutes to loosen remaining tissue, then clean manually.
5. Final Tissue Removal
•Use a soft toothbrush or fine brush to remove remaining tissue.
•Be careful not to dislodge small bones like phalanges or ribs.
6. Drying
•Place the cleaned bones on absorbent paper in a dry, well-ventilated area.
•Allow them to dry completely (1–2 day)
7. Assembly
•If you want a fully articulated skeleton:
•Arrange bones in an anatomical position.
•Use a small amount of glue or fine wire to hold bones together.
8. Labeling
•Label each part of the frog's skeleton
