Circulatory system in fish

• The circulatory system of fishes is responsible for transporting blood and nutrients throughout the body.
• It has a closed circulatory system, i.e. blood travels across the body through the network of blood vessels.
• Fish heart carry only deoxygenated blood that is why it is called as Venous heart.
• The circulatory system of fish is quite simple and consists of

Heart

Blood

Blood Vessels

a) Blood vessels

• The blood vessels are of two types, arteries and veins.
• The arteries are responsible for carrying oxygenated blood from the heart to the rest of the body, while the veins return deoxygenated blood from the different parts of the body to the heart.

b) The Heart

• In fishes, heart is a simple, two chambered, muscular structure that is located below the pharynx and immediately behind the gills.
• It is enclosed by the pericardial membrane or pericardium.
• In most of the fishes, the heart consists of an atrium, a ventricle, a sac-like thin-walled structure known as sinus venosus and a tube, known as bulbus arteriosus.