IV. Speak about the functions of the muscles

- smooth /visceral/

- striated /skeletal/

- cardiac

Read the text about the cardiovascular and respiratory systems of the human body. Find the passage, which contains the description of the heart. Read and translate the passage.

HUMANS

Part II: The Circulatory System. Respiration.

The cardiovascular system is the system of blood circulation. By the cardiovascular system we mean the heart, the arteries, the veins and the capillaries of the human body. The centre of the circulatory system is the heart. It lies in the thoracic cavity and has four chambers. The right heart consists of an upper chamber - the atrium or the auricle - and a lower chamber - ventricle. Between these two chambers is a one-way valve, the tricuspid valve. The left heart has two chambers, but the valve that separates them is called the mitral valve. The right heart receives blood (which is a red fluid) from the veins and pumps it into the lungs by way of the lesser circulatory system. In the lungs the blood receives oxygen. Then it moves into the left heart. From the left heart the well-oxygenated blood moves into a large artery, the aorta. The blood returns to the heart by means of the veins.

Blood vessels that receive blood from the ventricle and lead it away from the heart and towards other organs are arteries. The arteries continue to divide and form smaller and smaller vessels and finally divide into capillaries. Gradually the capillaries begin to join into larger vessels - the veins. The pulmonary vein carries the freshly oxygenated blood to the left auricle. The pulmonary artery and the pulmonary vein make up the pulmonary circulation.

The term “respiration” means the exchange of gases, which takes place between the living organism and the environment. It is the process by which the body cells and tissues make use of oxygen and carbon dioxide or the waste products of respiration are removed. Air is breathed through either the mouth or nose into oral cavity (pharynx). It then passes through the voice box (larynx) into the trachea. The trachea divides into two smaller tubes (bronchi), one is going to each lung. The bronchi divide into tiny passage-ways that are named bronchioles, which lead to air sacs (alveoli). The exchange of life-giving gases is effected through the walls of the alveoli.

Inhaled air contains about 20 per cent oxygen and four hundredths of one per cent carbon dioxide. Exhaled air consists of approximately 16 per cent oxygen and 4 per cent carbon dioxide. Nitrogen, which makes up about 79 per cent of the atmosphere, is not involved in the breathing process. When the air is inhaled into the lungs, a portion of the oxygen is passing into the blood and is being circulated through the body. At the same time, carbon dioxide is being diffused of the blood into the lungs and exhaled.

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