Frogs are a type of amphibians with a closed circulatory system. Hence, its blood only circulates through the blood vessels and heart. The circulatory system of frogs composes of two parts: the cardiovascular system and the lymphatic system. The main function of the cardiovascular system is to supply oxygen and nutrients to the tissues and to aid in the elimination of metabolic wastes while the lymphatic system drains the remaining plasma to the heart.
Key Areas Covered
1. Frog – Definition, Facts
2. How Does a Frog’s Circulatory System Work
– Blood Circulation of a Frog
Key Terms: Blood, Cardiovascular System, Circulatory System, Heart, Frog, Lymphatic System
Frog – Definition, Facts
Frogs are a type of amphibians. Hence, they are a kind of primitive vertebrates. Frogs live in both land and water. They lay their eggs in moist environments. The larval stage of frogs lives in water. They do not have legs and their respiration occurs through gills. The adult stage moves onto the land by developing legs. Since frogs have a larval stage, which is morphologically different from the adult stage, they undergo complete metamorphosis. Since frogs are one of the first primitive vertebrates to migrate to the land, their skin is thin, soft, hairless, and porous. It may contain both mucous and poison glands. The aquatic, larval stage breathes through gills while the terrestrial, adult stage breathes through the lungs. However, a part of the breathing occurs through the skin. Furthermore, frogs are cold-blooded animals and depend on sunlight for the regulation of body temperature. A frog is shown in figure 1.
Figure 1: A Frog
How Does a Frog’s Circulatory System Work
The circular system of a particular organism is composed of both the cardiovascular system and the lymphatic system. The main function of the cardiovascular system is to supply oxygen and nutrients to the tissues while that of the lymphatic system is to drain the remaining plasma in the form of lymph to the heart. The circulatory system of a frog is described below.
Cardiovascular System
Frogs have a closed circulatory system in which the blood flows only through blood vessels and the heart.
Blood
Blood is the circulating fluid within the circulatory system of frogs. 60% of blood contains plasma. The two types of frog blood cells found suspended within the plasma are red blood cells and white blood cells. Frog’s blood is red in color since it consists of hemoglobin.
Blood Vessels
The three types of blood vessels found in a frog are arteries, veins, and capillaries. Arteries are the thick-walled blood vessels that drain blood from the heart to all parts of the body. Veins are the thin-walled blood vessels that drain blood from tissues and organs to the heart. They consist of valves that prevent the backflow of blood. Capillaries are the smallest type of blood vessels through which the respiratory gases and nutrients exchange between the blood and the extracellular matrix of the tissues.
Heart
The heart of a frog is composed of three chambers: right auricle, left auricle, and a ventricle. The wall of the heart is made up of three layers; inner endocardium, middle myocardium, and outer epicardium. The two auricles are thin-walled while the ventricle is thick-walled. The right and left auricles are separated by the interauricular septum. The right auricle is larger than the left. The ventricle is muscular and spongy.
Mechanism of Blood Circulation
The right auricle receives deoxygenated blood from vessels that drain it from various organs of the body. It receives oxygenated blood from the skin and buccal cavity. Left auricle receives oxygenated blood from the lungs. Both right and left auricles drain blood into a single ventricle. Ventricle supplies blood to all parts of the body through three pairs of arches of aortae.
Figure 2: Frog’s Heart
Lymphatic System – Components and Mechanism
The lymphatic system of a frog is composed of lymph, lymphatic vessels, lymph heart, lymph spaces, and spleen. Lymph is the colorless fluid, which lacks some of the components of blood such as red blood cells and plasma proteins. Lymphatic vessels are equal to the veins and they drain lymph to the heart. Lymphatic capillaries arise from the lymphatic spaces, forming lymphatic vessels. Two pairs of lymph hearts are responsible for draining lymph into the veins from lymphatic vessels. The spleen is the reservoir of blood. It has many functions such as the production of antibodies and blood cells.
Conclusion
The circulatory system of a frog is composed of the cardiovascular system and lymphatic system. The cardiovascular system is composed of blood, blood vessels, and heart. The main function of the cardiovascular system is to supply oxygen and nutrients to the cells of the body. The lymphatic system of a frog is composed of lymph, lymphatic vessels, lymph spaces, lymph heart, and the spleen. The main function of the lymphatic system is to drain the remaining plasma in the form of lymph to the heart.
Reference:
1. “Circulatory System of Frog.” KULLABS.com, Available here.
2. “Lymphatic System of Frog (With Diagram) | Vertebrates | Chordata | Zoology.” Zoology Notes, 14 July 2017, Available here.
Image Courtesy:
1. “2516809” (CC0) via Pixabay
2. “The biology of the frog (Page 265, Fig. 72) BHL7720628” By Holmes, Samuel J. – (Public Domain) via Commons Wikimedia
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