Circulatory system , or cardiovascular, or vascular - is a great ramified transport system of animals and human. Continuously, throughout a humanrs

Circulatory system parts (organs) and function (meaning, role)

Circulatory system, or cardiovascular, or vascular — is a great ramified transport system of animals and human. Continuously, throughout a human’s life, it carries oxygen, nutrients, hormones throughout the body, taking away from the cells, tissues and organs waste products of metabolism, that is, performs hemodynamics (blood flow in the body). Consequently, the circulatory system provides: body feed, gas exchange, clearing it from the products of metabolism and humoral regulation of body functioning.

Blood moves through the blood vessels mainly due to the contraction of the heart. And its way into the body follows like this: heart → arteries → capillaries → veins → heart. The circulatory system — is a closed system. It consists of two circles of blood circulation — pulmonary and systemic. They were first described by an eminent English scientist William Harvey.


Heart is a hollow muscular organ. Its mass in an adult is 250-300 g. The heart is located in the chest cavity and is offset to the left of the middle line of the chest. It is contained in the pericardium formed by connective tissue. The inner surface of the pericardium secretes a fluid that moistens the heart and reduces friction during its contractions.

The structure of the heart meets his characteristic features. It is divided by solid partition into two parts — left and right, and each of them is divided into two interconnected sections: the upper — atrium and lower — ventricle. Therefore, the human heart, like in all mammals, four-chamber: it consists of two atria and two ventricles. The walls of the atria are much thinner than the ventricular wall. This is due to the fact that the work performed by the atria is relatively small. During their contraction, blood enters the ventricles, which perform significantly more work: push blood through the entire length of the vessel. The muscular wall (myocardium) of the left ventricle is thicker than the wall of the right ventricle, because it does a greater job. At the boundary between each ventricle and the atrium there are flap (cusp) valves (diagram 58) which are attached to the walls of the heart by tendon threads.

Diagram 58. Blood circulation: 1 — the temporal artery; 2 — temporal vein; 3 — front vein; 4 — jugular vein; 5 — carotid artery; 6 — upper hollow vein; 7 — aorta; 8 — pulmonary artery; 9 — pulmonary veins; 10 — shoulder veins; 11 — the heart; 12 — lower hollow vein; 13 — gastric artery; 14 — renal artery; 15 — ulnar artery; 16 — digital arteries; 17 — cubital vein; 18 — finger vein; 19 — femoral artery; 20 — femoral vein; 21, 22 — large tibial artery; 23, 24 — the tibia veins; 25 — plantar artery; 26 — plantar veins

During atrial contraction valve flaps hang down into the ventricles. Blood flows freely from the atria to the ventricles. When the ventricles are contracted, the valve flaps raise and close the entrance to the atrium. Therefore, the blood moves in only one direction: from the atria to the ventricles. It is ejected from the ventricles into the vessels.

Blood vessels

All human body is permeated with blood vessels. According to their structure, they are all different.


The arteries are the vessels that carry blood away from the heart. They have strong elastic walls that include smooth muscle. When contracting, the heart ejects blood into the arteries under a high pressure. Due to its density and elasticity of the artery walls withstand the pressure and stretch.


Large arteries branch out as go away from the heart. The smallest arteries (arterioles) branch into thin capillaries (diagram 59); there are about 150 billion of them in the human body. The walls of capillaries are formed by a single layer of flat cells. The substances dissolved in the blood plasma, come into tissue fluid and then get into cell through its wall. Cell waste products penetrate from the tissue fluid into the blood through the capillaries walls. Taken from

Coronary arteries: 1 — aorta; 2 — left main coronary artery; 3 — left circumflex artery; 4 — the left anterior descending artery; 5 — right coronary artery
Heart valves: 1 — aorta; 2 — pulmonary trunk; 3 — the valve of pulmonary trunk; 4 — aortic valve; 5 — mitral (two-folded) valve; 6 — tendon strands; 7 — tricuspid heart valve
Heart valve types: a) two-folded (two cusp); b) three-folded (three cusp)
Diagram 59. Capillary mesh: 1 — arterioles; 2 — venule; 3 — capillaries


Blood from capillaries flows in the veins — vessels through which the blood flows to the heart. The pressure in the veins is slight, so their walls are significantly thinner than arteries’.

  • What organs and parts are in circulatory system?

  • Describe the biological function of the circulatory system.

  • Sketch out the direction of blood flow in the cardiovascular system.

  • What are the advantages of the four-chamber heart?

  • Determine the relationship of structure and functions of the heart.

  • What parts has the heart?

  • Explain the function of the heart chambers.

  • Identify the relationship of the structure and functions of the heart walls.

  • Explain the biological significance of the heart valves.

  • Why all healthy heart valves open and blood passes only in one direction?

  • What is relationship between the structure and functions of blood vessels?

  • How the artery maintains a high blood pressure?

  • Describe the function of smooth muscles of arteries.