Frog Heart Structure & Vena Cava — NEET Biology

The vascular system of frog is well-developed closed type. Frogs have a lymphatic and blood vascular system composed of heart, blood vessels and blood. The lymphatic system consists of lymph, lymph channels and lymph nodes. Heart is a muscular structure situated in the upper part of the body cavity. It has three chambers, two atria and one ventricle and is covered by a membrane called pericardium. A triangular structure called sinus venosus joins the right atrium. It receives blood through the major veins called vena cava. The ventricle opens into the left atrium. From the heart, purified blood goes into the ventral aorta on the ventral side of the heart. The ventral aorta then branches into aortic arches. The veins collect blood from different parts of body to the heart and form the venous system. Special venous connection between liver and intestine is present in frogs called hepatic portal system; similarly, the one present is called hepatic portal system and the latter is called renal portal system. The blood is composed of plasma and cells. The blood cells are RBC (red blood cells or erythrocytes, WBC (white blood cells or leucocytes and platelets. RBCs are nucleated and contain red coloured pigment namely haemoglobin. Blood carries nutrients, gases and other important proteins and RBCs. The blood carries nutrients, gases and water to the respective sites during the circulation. The circulation of blood is achieved by the pumping action of the heart.