MOOC- To study the dissection of Frog

 Introduction

Frogs are vertebrate amphibians commonly used in dissection for biology laboratories to study morphological and anatomical structure. Although the structural features of humans and frogs have a huge difference but the basic body plan is similar.  The study of the anatomy of frogs will explore and understand the various anatomical structure and how they work.  In addition, It also emphasizes the evolutionary adaptations regarding how they change an aquatic life to life on land. This experiment requires a few essential materials for the dissection of the frog.  

Materials Required

Provide each work area with the following materials:

1. Frog specimens
2. Dissecting Pad
3. Dissection Box
4. Protocol for Frog Dissection
5. Paper towel or Tissue paper
6. Gloves

Safety

1. Wear gloves and appropriate apron before handing and dissecting of the frog specimens.
2. Be careful during handling of dissecting instruments.
3. Wash your hands with soap after carrying out an experiment.

Observe external morphology of Frog

1. Place the preserved frog in your dissecting tray
2. Observe the frog. Feel the smooth and pliable skin. Note the coloration on all parts of the body.
3. The division of a frog’s body includes the head, trunk, and limbs or legs as shown in Figure 1. All frogs lack necks and tails. Examine the front and hind limbs of the frog. Find the digits, which are finger-like projections on the forelimbs and hind limbs. Locate the hind limbs, which are the longer and more muscular limbs of the frog. A hind limb consists of a thigh, shank, ankle, foot, and webbed toes. Locate the forelimbs, which are shorter than the hind limbs. A forelimb consists of an upper arm, wrist, hand, and fingers.
4. Looking at the head, identify the 2 external nares at the head’s tip. These function as a means of respiration.
5. Find the round tympanic membranes that form the frog’s external sound receptors. You will find these on the backside of the eyes.
6. Look closely at the eyes and attempt to find the frog’s third eyelid; this is the nictitating membrane that moistens and protects the eye. As the frog is deceased, this will appear as a cloudy eyelid attached at the bottom of the eye; however, it would appear clear in a living frog.
7.  Identify the cloaca, located at the specimen’s posterior end. The cloacal opening provides the function of exit for all urinary, reproductive, and digestive systems.
8. Reposition the frog to lie on its dorsal side.
9. Carefully cut the jaw joints on each side of the mouth to enable you to open the mouth wide.
10. Locate the glottis (leads to the lungs) and esophagus opening (leads to the stomach).
11. Conduct a dental analysis. You will find 2 sets of teeth. Firstly, locate the fine maxillary teeth lining the upper jaw. Secondly, locate the two prominent vomerine teeth located behind the mid-region of the upper jaw.
12. On the sides of the roof of the frog’s mouth, you should see 2 openings; the eustachian tubes that lead to the tympanic membranes you identified earlier. The function of these tubes is to aid in pressure equalization.

Figure 1 Showing external morphology of frog (https://www.unilearn.net.au)

Examine the anatomical various structure of frog

Figure 2 showing dissection manual of Frog (https://www.unilearn.net.au)

1. Place the frog on the dissecting tray, the ventral surface facing up.
2. Using scissors, cut into the frog’s abdomen. To do this, pinch the skin at the frog’s stomach and make a small cut at the center.
3. Slice through the skin, keeping your cuts as straight and clean as possible. Follow the cutting pattern in Figure 2.
4. Using the same pattern, slice through the layers of muscle until you reveal the internal organs beneath.
5. Locate the frog’s liver in the abdomen body cavity; it will be comparatively large in size and brown. The largest internal organ, the liver consists of 3 lobes.
6. Reposition the liver lobes to reveal gallbladder beneath. The gallbladder, which stores bile, will appear significantly smaller and greenish.

Identify the following major organs of the frog  as shown in Figure 3:

1. Stomach
2. Small intestine
3. Large intestine
4. Spleen
5. Heart
6. Lungs
7. Fat Bodies
8. Ovaries
9. Oviduct
10. Kidney

Figure 3 showing the anatomical structure of the frog (https://media.vwr.com)

Video tutorial: 

https://www.youtube.com/watch?v=9Y8Ysek4Vac

Sources

• https://www.astephensscience.com/uploads/4/0/7/3/40734789/forg_dissection_2017.pdf
• https://www.southernbiological.com/frog-dissection/
• https://www.unilearn.net.au/Courses/Labs/UNL44/ACT6/Frog%20Dissection%20additional%20information.pdf
• https://media.vwr.com/emdocs/scied/frog_guide_03.pdf