Fish are vertebrates. Such organisms have a skull, spine and paired limbs, in this case fins. The fish class is divided into two classes:

The class bony fish, in turn, is subdivided into several super-detachments:

  • Cartilage ganoids.
  • Lungfish fish.
  • Cistepere fish.
  • Bony fish.

The circulatory system of fish: cartilage and bone

The main difference of all fish is the presence of one circle of blood circulation, as well as a two-chamber heart, which is filled with venous blood, with the exception of only cross-shaped and double-breathing fishes. The structure of the circulatory system of fish (bone and cartilage) is similar, but still has some differences. Below will be considered both schemes.

Circulatory system of cartilage fish

The heart of cartilaginous fish is composed of two parts cameras. These cameras are called this way: the ventricle and the atrium. Near the atrium is a thin-walled venous sinus, it joins the venous blood. The end (if viewed from the side of blood flow) part of the ventricle is the arterial cone, which is part of the ventricle, but it looks like the beginning of the abdominal aorta. In all parts of the heart is cross-striped muscles.

The abdominal aorta moves away from the arterial cone. Five pairs of gill arteries originate from the abdominal aorta and depart to the gills. Arteries in which blood flows toward the gill filaments are called the gill-bearing arteries, and in which oxidized blood flows from the gill lobes — the outgoing gill arteries.

The carrying arteries fall into the roots of the aorta, and they, in turn, merge and form the dorsal aorta - the main arterial trunk. It is located under the spine and supplies blood to all the internal organs of the fish. From the aortic roots to the head, the carotid arteries stretch.

From the head, venous blood flows through the paired cardinal veins, which are also called jugular. The blood from the body flows through the paired posterior cardinal veins. They merge with the jugular veins near the heart and form the Cuvier ducts of the corresponding side, then flow into the venous sinus.

In the kidneys, the cardinal veins form the so-called portal blood circulation system. In the intestinal vein, blood flows from the intestine. The portal system of blood circulation is formed in the liver: the intestinal vein brings blood, and the hepatic vein carries it into the venous sinus.

Bone fish circulatory system

Almost all species of bony fish abdominal aorta has a swelling, which is called the arterial bulb. It consists of smooth muscles, but similar in appearance to the arterial cone of the circulatory system of cartilaginous fishes. It should be noted that the arterial bulb can't throb.

Arterial arcs (bringing and carrying out arteries) are only four pairs. In most species of bony fish, the venous system is designed so that the right cardinal vein is continuous, and the left one forms the portal system of the blood circulation in the left kidney.

The circulatory system of fish is simpler than that of amphibians and reptiles, but it has some rudimentary vessels like frogs and snakes.


Considering how the blood circulatory system of fish is arranged, it is worthwhile to pay special attention to the short-breathing ones, since they have some peculiarities.

The most important feature of this super-detachment is the presence of pulmonary, besides gill respiration. The organs for pulmonary respiration are one or two bladders that open near the esophagus on the ventral side. But these formations are not similar in structure to the swimming bladder of bony fishes.

Blood flows to the lungs through vessels that branch from the fourth pair of Gill arteries. They are similar in structure to the pulmonary arteries. From the so-called light going vessels. As it enters the blood in the heart. These special vessels are homologous in structure of the pulmonary veins of terrestrial animals.

The atrium is partially divided by a small partition into the right and left parts. From the pulmonary veins, blood enters the left half of the atrium, and all the blood from the posterior vena cava and the Cuvier ducts into the right half. Vena cava is absent in fish; it is characteristic only for terrestrial animal species.

The circulatory system of fish in the superorder is Laconstriated, evolved and is a precursor to the development of this system of terrestrial vertebrates.

Blood composition

  • Colorless liquid - plasma.
  • Red blood cells - red blood cells. They contain hemoglobin, which dyes the blood red. These same elements carry oxygen through the blood.
  • White blood cells - white blood cells. Take part in the destruction of foreign microorganisms in the body of the animal.
  • Platelets affect blood clotting.
  • Other elements of blood.

The relative weight of blood to body weight in fish is about 2-7%. This is the smallest percentage of all vertebrates.

The value of the circulatory system multifunction. The tissue, organs and cells of a living organism receive oxygen, minerals, fluid. Blood makes some products of metabolism: carbon dioxide, slag, etc.

It should be noted that the lymphatic system acts as a mediator between the blood and tissues. The lymphatic system is a system of blood vessels that contains a colorless liquid called lymph.

General conclusions

Blood refers to connective tissue. It enters the bloodstream from the intercellular space. The circulatory system of fish is not much different from other vertebrates.