Circulatory system of fish

The circulatory system of bone fishes of any kind, like fish of cartilaginous, has a single structure. In the body there is only one circle of blood circulation. Schematically, the departments of the circulatory system of the fish represent the following chain of consecutive components: heart, abdominal aorta, arteries on the gills, dorsal aorta, arteries, capillaries and veins.

The heart of fish has only two chambers and is not adapted, like other creatures, to perform the function of separating the blood stream enriched with oxygen from blood not enriched with oxygen. Structurally the heart represents four chambers, located one after another. All these chambers are filled with special venous blood, and each of the heart divisions has its name - venous sinus, arterial cone, atrium and ventricle. The heart divisions are separated from one another by a valve, as a result of which the blood can move only in one direction, when contracting the cardiac muscles - in the direction from the venous sinus to the arterial cone. The circulatory system of the fish is arranged in such a way that the blood flow is carried out exclusively in this direction and in no other way.

The role of the channels for the distribution of nutrients and oxygen along the body of the fish is performed by arteries and veins. Arteries perform the function of transporting blood from the heart, and the veins to the heart. The artery contains oxygenated (oxygenated) blood, and in the veins - less oxygen-rich blood (deoxygenated).

Venous blood enters a special venous sinus, after which it is delivered to the atrium, ventricle and abdominal aorta. The abdominal aorta is connected to the gills through four pairs of vascular arteries. These arteries disintegrate into a number of capillaries in the gill petal area. It is in the gill capillaries that the process of gas exchange takes place, after which these capillaries merge into the outgrowth of the gill arteries. Arterial arteries are part of the dorsal aorta.

Closer to the head, branches of the dorsal aorta pass into the carotid arteries. The circulatory system of the fish implies the division of each carotid artery into two channels - internal and external. The internal carotid artery is responsible for the supply of blood to the brain, while the external one performs the function of blood supply to the visceral part of the skull.

Closer to the back of the fish body, the roots of the aorta merge into a single dorsal aorta. Sequentially unpaired and paired arteries branch from it, and the circulatory system of fishes in this part supplies blood to the somatic division of the body and important internal organs. The dorsal aorta ends with the caudal artery. All arteries branch into many capillaries, in which the process of changing the composition of the blood occurs. In the capillaries, the blood becomes venous.

Purification of blood and its further current is carried out according to the following scheme. In the head region, the blood concentrates in the anterior cardinal veins, and in the lower part of the head it gathers in the jugular veins. Passing from the head to the tail vein, in the back part is divided into two parts - the left and right renal portal veins. Next, the left portal vein branches, forming a system of capillaries that form the collar system of the kidney located on the left. In most bone species, the circulatory system of fish is arranged in such a way that the right portal system of the kidney is usually reduced.

From the kidneys, the circulatory system of fish drives the blood into the cavity of the posterior cardinal veins. The anterior, posterior, and cardinal veins on each side of the body merge into the so-called Cuvierian ducts. The Cuvierian ducts on each side are connected to the venous sinus. As a result, the blood transferred by the current from the internal organs enters the portal vein of the liver. In the region of the liver, the portal system branches into many capillaries. After that, the capillaries merge again and form a hepatic vein, which is connected to the venous sinus.