Dissecting a frog is a common and important experience in introductory biology or anatomy. Learning to recognize and understand the intricate mechanisms of the internal organs can be a memorable and immersive experience for students, but it can also be frightening for others. Learning to do the task scientifically can help you identify the frog's large organs quickly and efficiently, so you can go through the process without a hitch.
Step
Part 1 of 5: Getting Started
Step 1. Prepare the surgical tray and pick up the frog
Frogs and other small animals are usually dissected in a biology laboratory to study anatomy. If your class is going to dissect frogs, the teacher should provide all the necessary equipment for the activity. However, not much is needed. Usually a clean surgical tray is required, which is almost like a cake pan with a rubber coating on the bottom. To make the incision, you will need a sharp scalpel and a pair of tweezers, or another type of piercing tool, surgical tongs, lab instructions, and a frog.
In the past, advanced science students were required to kill their own frogs, using chemicals. Although in this way the frogs are still fresh to dissect, this practice is now somewhat rare. Generally, the frogs used are frogs that have been dead for a while
Step 2. Look at the complementary materials/materials provided by the teacher
Most frog dissection instructions describe basic recognition procedures. You are required to open the frog, identify its basic organs and systems, explore its anatomy, and perhaps fill out a brief laboratory report to complete the activity. Adhere to the material provided by the teacher.
If you don't feel comfortable dissecting frogs in class, tell your teacher. Digital surgical alternatives are also available
Step 3. Wear appropriate safety equipment
Use of latex or rubber gloves, safety goggles, and hygiene are important. Generally, the surgical object is sterile and safe, but it is still very important to keep the hands, eyes and mouth free from formaldehyde (formalin) which is used to preserve the frog to be dissected. Sit up straight while working, wear the protective materials provided, and wash your hands thoroughly afterward.
Step 4. Place the frog on the surgical tray
To begin surgery, remove the frog from its package and place it on the tray in a supine position. Some frogs will feel a little stiff from the preservative, so you'll need to massage them gently, bending their legs and loosening the joints so that the frog can lie on its back comfortably.
Part 2 of 5: Checking the Outside
Step 1. Identify the gender of the frog
The easiest way to tell the difference between a male and female frog is not to look between the crotch, but between the four legs. The thumb pads on the male frogs' forelegs are fatter, and the thumbs appear lumpy and fatter than the thinner toes of the female frogs.
If the surgical object is a female frog, watch for eggs and ovaries, which need to be removed before you can identify specific organs
Step 2. Check the head
On a frog's head, most labs will ask you to mark and identify some important parts. The eye and the thin covering that covers the eye, so that the frog can see underwater, are the most important and, perhaps, easiest to find on the frog's head. You can find and mark the mouth.
The external nare is the technical term for a frog's nostrils, which are used for breathing and protrude forward, above the mouth. Each tympanum (the lining of the middle ear) is located behind the eye, and is a round, slightly flattened dot that is used to detect sound
Step 3. Examine the inside of the mouth
Use a scalpel to cut through the membranes that connect the joints of the frog's mouth and open its mouth wide to examine the inside. You can see and mark the esophagus, which is connected to the stomach, and the vocal folds, which are connected to the lungs. It is also easy to recognize the tongue, which is quite large and elastic.
- The eustachian tube is on the left and right of the back of the throat, and is used to distribute pressure.
- The "vomerine" teeth are behind the maxillary (upper jaw) teeth, although both are used to store prey in the mouth.
Step 4. Find the cloaca
The cloaca is the part where the first incision is made, which is between the frog's hind limbs. Use scissors to remove the abdominal muscles from the opening in the cloaca, if necessary, and make incisions if you are told to. Waiting for certain instructions in the lab at all times is important.
Step 5. Open the frog as instructed
Each instructor has a different opening technique, but generally you'll start with the basic "X" pattern: a single cut under each leg, connected to an incision above the abdomen. Start with an incision toward each leg, then connect with a straight incision above the "girdle" in the center of the frog's stomach.
Cutting the body in an "H" pattern is also common. To do this, make a transverse (horizontal) incision on the inside of the arm and leg, and connection with a side incision above the abdomen. This will create two large incisions that you can pull and open, clipping them into the tray if necessary
Step 6. Lift the body wall incision and clamp it back
To remove the skin and open the frog, it is common to pull the skin back and attach it to the bottom of the tray with tongs. Gently tug until it engages with the bottom of the tray, then use tongs at each corner to secure the peel. Be careful not to tear the skin.
Step 7. Remove the stomach lining
There is a cobweb-like membrane covering many of the organs, which you must carefully remove so that the internal organs can be clearly seen. Slice carefully to make holes in them, being careful not to pry out any organs, then loosen and remove them from the holes to reveal the organs and move on.
Part 3 of 5: Recognizing the Main Internal Organs
Step 1. Find body fat
These organs look like a grid of tubes that are orange and yellow as bright as spaghetti along the abdominal wall. If the frog is bigger, its body fat may need to be removed to see the other organs. If you're having trouble seeing the organ behind this section, check with your teacher to make sure it's OK to remove the section before continuing with the process.
Step 2. Find the heart
This organ is the largest organ in the frog's body, and the easiest to find. They are usually brown in color and consist of three large lobes or structures. Sometimes, this organ is also streaked with a greenish or bluish tint.
Generally, this organ will not be removed first, if it has not been recognized. These organs can help accurately describe the frog's anatomy, and find other organs that are related to the ones you already recognize. However, follow the teacher's directions, and remove the organs when the time comes
Step 3. Get to know the heart
The heart is triangular in shape, and is located above the heart. The organ consists of the left and right chambers above and the ventricles (small cavities) that run along the bottom of the heart. Conus arteriosis is a large vessel that exits the heart and pumps blood throughout the body.
Step 4. Find the lungs under the heart and liver
The lungs of the heart are quite small, shaped like tiny peas, and have a spongy texture. To find it, you may need to pull out your lungs and heart. If you're having trouble finding your lungs, you're not alone. Ask the teacher for help if you have trouble.
Step 5. Locate the gallbladder
There is a small, greenish pouch under the lobe of the liver, which stores bile for the digestive system. This organ is usually quite prominent, because it looks very much like snot.
Step 6. Trace the esophagus to find the stomach
The esophagus is a tube that starts at the mouth and ends in the stomach. Open the frog's mouth and find the esophagus, then slowly push the stemmed needle, and see where the esophagus leads. Traverse the tube to find the stomach and begin examining the digestive tract, your next big step in the surgical process.
Part 4 of 5: Removing the Stomach and Digestive Tract
Step 1. Remove the liver and intestines and remove the two organs to find the stomach
If you haven't already done so, simply remove the heart to continue exploring the hole in it. The belly is curved under the heart. Once you find the stomach, trace its curve downwards for the pyloric sphincter, which is a valve that carries digested food into the small intestine.
Step 2. Get to know the small intestine
The small intestine is an organ that is connected to the end of the stomach, and consists of the duodenum and the end of the small intestine, which are connected to the mesentery. The blood vessels that run from the mesentery are used to transport energy from digested food from the intestines into the bloodstream. That's how frogs get their strength and energy from their food.
Trace the small intestine to the large intestine. The large intestine, also known as the cloaca, is dilated at the bottom of the small intestine. This is where the feces come out of the frog's body
Step 3. Find the spleen
The frog's spleen is blood red, and is shaped like a small ball. This is where blood is stored during the digestive process, which helps carry energy from the frog.
Step 4. Carefully open the belly
Depending on your assignment, some teachers will ask you to open the frog's belly and others may not. Always follow their instructions.
If the procedure is part of the activity, carefully use the scalpel to open the frog's belly with a horizontal incision, opening it slowly with small incisions. Turn your face away, in case there is a burst from the frog's stomach. What do you see in there?
Part 5 of 5: Recognizing the Urogenital System
Step 1. Find the kidney
In frogs, their reproductive and excretory systems are connected. The kidney is a flat, bean-shaped organ that can be found in the same location as in humans, rising on the lower back, near the spine of the frog. Also similar to the human anatomy, the color is relatively dark, sometimes visible because of the yellow body fat, which is connected at the top.
You probably won't be removing any organs from the frog at this point. You should have removed whatever was needed to find and identify all the previous organs, so removing them now is unnecessary
Step 2. Find the genitals
Confusingly, the genitals of frogs can look very similar to those of males, due to a phenomenon known as the vestigial oviduct. The best way to tell the difference is to look for the testicles. If you don't see testes, it means it's a female frog.
- If it's a male frog, find the testicles above the kidneys. The testes are pale and round in shape.
- If it's a female frog, find the oviduct. There is a curly part outside the kidney, where the female frog lays her eggs.
Step 3. Get to know the bladder
The bladder is a visibly empty pouch in the lowermost cavity of the body, which stores urine and expels it from the body through the cloaca, the small opening where you start the incision. Frogs excrete all the feces and sperm through this small opening.
Step 4. Identify all the organs on the laboratory report
Usually, a diagram of the frog's organs will be shown, which you need to mark. Each laboratory may have specific assignments or exams that must be completed as part of the activity. Before you dispose of the frogs, complete the required written assignments.
Step 5. Clean your workplace
Throw the frogs away after you finish the written task. In the laboratory, there is usually a special disposal area and a place to clean surgical trays. Clean the tray with soap and water, remove gloves, and wash your hands thoroughly.
It may take several cleanings to get the smell of preservatives off your hands, so you'll need to scrub again a few hours later
Necessary Items
- Frog
- Surgical tray/tray
- Scalpel or razor blade.
- Clamp
- Scissors
- Latex or rubber gloves
- Plastic, newspaper or paraffin paper to cover the workplace
- Cotton balls or napkins
