Frog Dissection

Leopard Frog

Kingdom: Animalia

Phylum: Chordata

Subphylum Vertebrata

Class: Amphibia

Order: Anura

Genus: Rana

Species: Rana pipiens

I. Purpose:

To examine the frog externally and internally by dissection.

II. Materials:

1. Frog

2. Dissection pan

3. Manual

4. Dissection utensils

III. Methods:

A. External:

The dissectors set up for their lab by getting the following materials: the frog,

dissection utensils, dissection manual, and the dissection pan. Dissectors placed the

frog anteriorly with the dorsal side up. Dissectors noticed that the body of the frog

was divided into 3 regions: the head, neck, and trunk. Dissectors also noticed that

the frog had a smooth, protective skin. The skin contained mucus glands to keep it

moist, and it also had pigment cells to regulate its color. Dissectors found 2 forelegs

(which is made up of an upper arm, forearm, wrist, hand, and digits) on the trunk of

the body. Dissectors also found the hind leg ( composed of the thigh, shank, ankle,

foot, and digits) on the trunk of the body. The forelegs were located more anteriorly

than the hind legs. Dissectors also noticed that the forearm had 5 digits while the hind

leg only had 4 digits. The dissectors found 2 nostrils, nares, located on the anterior

part of the head. Posterior to the nares, the dissectors found the eyes. The eyes

had an upper and lower eyelid, as well as a third lid, the nictitating membrane (which

covers the eye while the frog is swimming). Dissectors peeled a portion of the

nictitating membrane off using the blunt probe. Dissectors found the tympanic

membrane, the eardrum, just right behind the eyes. Dissectors opened the mouth of

the frog with their hands, and made an extra posterior cut where the 2 jaws met with

the scalpel. Dissectors opened up the mouth of the frog and looked at the structures

within. Dissectors found the 2 different pairs of teeth: the maxillary (which go all

around the upper jaw), and the vomerine (teeth/bumps on the upper jaw). Dissectors

rubbed their fingers across the teeth to feel the rough surfaces. The dissectors also found the internal nares which are located on the roof of the mouth. Attached to the lower jaw, the dissectors found the tongue. Dissectors felt the tongue with their fingers and found it thick and sticky. Dissectors noticed that the mouth cavity narrowed posterior to form the pharynx, which then leads to the pharynx. Dissectors found the glottis, a structure that guards air passage to the lungs, just ventral to the opening for the esophagus. The Eustachian tube was also found lateral and anterior to the glottis. External observations were completed, so the dissectors got ready for the internal observations.

B. Internal:

Dissectors began the internal observations by placing the frog ventral side up on the dissection pan. To take off the skin, the dissectors had to pull a little section of the skin up with the forceps in the region between the hind legs meet. Then, the dissectors made a midline cut with the dissection scissors from the junction of the hind legs to the mandible. Dissectors then made lateral cuts with the dissection scissors at each end of the cut. Dissectors then peeled off the skin from the entire frog with their hands. Dissectors also observed the skin through the light and saw how thin and somewhat clear it was. Dissectors observed the abdominal muscles. Dissectors also noticed a thick yellowish substance, fat, scattered around the body. Dissectors then made cuts similar to those in which they made to peel off the skin with the dissection scissors. Dissectors opened up the area in which was cut open and pinned it down to the dissection pan. Dissectors found the short esophagus just posterior to the mouth. Posterior to the esophagus, the dissectors found the stomach. Dissectors followed the stomach posterior, and found the small intestine. Dissectors found the two separate regions of the small intestine: the duodenum (the upper portion) and the ileum (the coiled middle portion). The dissectors found the large liver (three-lobed) directly anterior to the stomach. The role of the liver is to secrete bile. Dissectors found the gallbladder (sac-like structure which stores bile) directly under the left lobe of the liver. The dissectors found the pancreas (organ that secretes digestive enzymes into the small intestine); the pancreas was tan colored and upheld by mesentery (a fan-like membrane which holds