Dissection of a Rana catesbiana (Bull Frog) - Introduction

The dissection of a bull frog is completed during the study of human anatomy as a means of physically seeing and comparing anatomical structures. Many of the structures, organs and systems of the frog are similar to those of humans, who are also vertebrates; however, as amphibians, frogs also have some differences. During this lab both these similarities and differences will be examined.

Frog’s development is unique in that they go through metamorphosis. They begin their lives as aquatic, free-swimming, tailed, fish-like tadpoles. During this phase they live in water, use gills to obtain oxygen, and eat plant matter. Frogs then go through a metamorphosis, or transformation, during which their tail is reabsorbed and disappears, powerful hind legs develop, forelegs then develop, the gills are replaced with lungs and the frog begins eating insects instead of plants.

Frogs are part of the class Amphibia, which is the smallest class of vertebrates. Their full classification is:
Kingdom – Animalia
Phylum – Chordata
Class – Amphibia
Order – Salientia
Family – Ronidea
Genus – Rana
Species – catesbiana


For centuries, frogs have served man well. Many advances in medical knowledge were first detected in the lowly frog. This is true not only in the study of anatomy, but also in such diverse areas as physiology, embryology, ecology, and behavioral biology. A series of important biological discoveries were made during examiniations of the frog. The English physician William Harvey (1628) described the circulation of the blood and the structure of the frog heart. Malpighi, an Italian scientist (1661), first observed and explained the role of capillaries after viewing the lungs of frogs. The famous Dutch microscopist Anton van Leeuwenhoek (1688) described the capillaries of tabpole gills and the red blood cells of frogs. Luigi Galvani (1786) discovered the electrical nature of nerve impulse transmission and muscle contration while experimenting with frogs.