how to dissect a frog 2014

How to Dissect a Frog

“Looks aren’t everything. It’s what’s inside you that really matters. A

biology teacher told me that.”

First, measure the length of your frog. Remember to use centimeters.

Determine the frog’s sex, by looking at the fingers, on its forelegs. A male frog usually has thick pads on its "thumbs.”

Locate and identify the external features of the head. Find the mouth, external nares, tympani, eyes, and

nictitating membranes.

Cut the hinges of the mouth and open it wide.

Identify the structures inside the mouth. Find the vomerine teeth, the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the

esophagus, the pharynx, and the glottis.

Remove the tongue. Measure the length.

Place your frog on a dissection tray, ventral side up.

Look for the opening to the frog’s cloaca, located

between the hind legs.

Lift the skin and use scissors to cut along the center of the body from

the cloaca to the lip.

Turn back the skin, cut toward the side at each leg, and pin the skin flat.

use scissors to cut through the muscle. Turn scissors sideways when

you reach the breastbone..

Make three horizontal cuts. One above the

shoulders, one below the shoulders and one just

above the legs.

Turn back the muscles, and pin the them flat.

Open up the body cavity. If your frog is a female, the abdominal cavity may be filled with dark-colored eggs. Remove the eggs

so you can see the organs under them.

Use the diagram below to locate and identify the organs of the digestive system: esophagus, stomach, small intestine, large

intestine, cloaca, liver, gallbladder, and pancreas.

Find the heart.

Find the left atrium, right atrium, and

ventricle of the heart. Find an

artery attached to the heart and another artery

near the backbone. Find a vein near one of the shoulders.

Carefully lift the liver and locate the gallbladder beneath. Remove only the liver.

Find the lungs.

These are usedwhen the frog is out of the water.

Identify the parts of the digestive system

Mouth

Pharynx

Oesophagus

Stomach

Intestine

Rectum

Cloaca

How is a frog’s digestivesystem differentthan a humans?

Identify the digestive system.

Carefully remove the digestive system. Cut at the esophagus and the cloaca. Lift out.

Measure the small intestine. Open the stomach and intestines.

Open the stomach.

Remove the peritoneal membrane, which is connective tissue that lies on top of the red kidneys.

Find the ureters; the urinary

bladder; the testes and sperm ducts in the male; and the ovaries, oviducts,

and uteri in the female.

Dissecting the brain.

Removing the frog's brain is a difficult thing to do, the skull is very thin and care must be taken to carefully remove the top of the skull where the brain is seating. The best tool for the job is a scalpel, where you scrape the top of the head, right between the eyes

When the brain is removed it will look like this.