Describe the circulatory system of a frog.

(A) $\rightarrow$ The vascular system of a frog is a well-developed closed type. It also includes a lymphatic system.
$\rightarrow$ The blood vascular system involves the heart,blood vessels,and blood.
$\rightarrow$ The lymphatic system consists of lymph,lymph channels,and lymph nodes.
$\rightarrow$ Heart of Frog: The 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 the pericardium.
$\rightarrow$ $A$ triangular structure called the sinus venosus joins the right atrium. It receives blood through the major veins called vena cava.
$\rightarrow$ The ventricle opens into a sac-like conus arteriosus on the ventral side of the heart. The blood from the heart is carried to all parts of the body by the arteries.
$\rightarrow$ The veins collect blood from different parts of the body and return it to the heart,forming the venous system.
$\rightarrow$ Portal system: Special venous connections between the liver and intestine (hepatic portal system) as well as the kidney and lower parts of the body (renal portal system) are present in frogs.
$\rightarrow$ Blood: Blood consists of blood plasma and blood cells.
$\rightarrow$ Blood cells include $RBC$ (red blood cells) or erythrocytes,$WBC$ (white blood cells) or leucocytes,and blood platelets. The circulation of blood is maintained by the pumping action of the muscular heart.
$\rightarrow$ $A$ red-coloured pigment,namely haemoglobin,is present in red blood cells. These cells are nucleated.
$\rightarrow$ Lymph: Lymph is different from blood because it lacks proteins and red blood cells. During circulation,the blood carries nutrients,gases,and water to the respective sites.