• The blood carries nutrients from the intestines through the body;
• The blood brings oxygen to the cells, and carries away carbon dioxide and other metabolic products.;
• Blood cells protect us from harmful microorganisms.;
• The blood carries hormones and other biologically active substances that regulate the body’s activity throughout the body.;
• Blood maintains a constant temperature of vital organs

The heart must contract evenly and strongly to ensure a continuous flow of fluid, and the vessels must ensure the delivery of blood to every cell in the body. The heart is a hollow muscular organ formed by a special cardiac muscle tissue that makes up the myocardium. It is located in the pericardium sac, formed by two sheets of connective tissue. There is a liquid between them that reduces friction. The heart is divided by a continuous longitudinal partition into two halves: the right contains venous blood, and the left contains arterial blood. The heart is divided by transverse partitions into chambers: two atria and two ventricles. Thanks to special valves, blood can move only in one direction – from the atria to the ventricles, and from there through the arteries to the tissues of the body.

The wall of large blood vessels consists of three layers: the inner, formed by epithelial tissue, the middle, consisting of elastic fibers and muscle tissue, and the outer, formed by connective tissue. Due to elastic fibers and muscles, the arteries are able to withstand the high pressure of blood being pushed out of the heart. When muscle fibers contract, vascular tone increases, blood vessels narrow and blood pressure increases. The vein wall also consists of three membranes, but they contain fewer elastic fibers than the arteries, so they are less elastic and more stretchable. There are special valves inside the veins that prevent blood from flowing back. Since the pressure in the veins is low, blood flows slowly through them and can stagnate, especially in the legs, causing the veins to dilate. To prevent this process, it is advisable to use special exercises for the legs and generally move more. And vice versa: prolonged immobility “on your feet” can lead to varicose veins. The smallest human blood vessels are capillaries in which substances and gases are exchanged between blood and tissue fluid. Their wall consists of a single layer of cells that are permeable not only to many substances, but also to some blood cells (for example, phagocytes that devour microbes that enter our body). The diameter of the capillaries is small, and their total number in the human body is huge – more than 150 billion. For the normal functioning of capillaries, vitamins are needed, in particular vitamin C. It strengthens their walls and prevents hemorrhages.

Normal blood pressure in the brachial artery in young and middle–aged people is 110-120 mmHg during cardiac contraction (systolic pressure) and 70-80 mmHg during its relaxation (diastolic). Blood pressure tends to increase with age. Its persistent increase is called arterial hypertension. For some elderly people, a sharp increase in blood pressure can be fatal. Therefore, to increase your life expectancy, you should monitor your blood pressure, keeping it within certain limits. The amount of blood pressure depends on two factors: the intensity of the heart and the width of the vascular lumen. Thus, you can reduce blood pressure either by slowing down the work of the heart, or by dilating the blood vessels. To do this, in addition to pills, you can use various methods of self-regulation (for example, auto-training) and relaxation techniques, which we will discuss in the fifth chapter of the book. A healthy heart has the ability to flexibly adjust its work when external conditions change (slow down its rhythm during sleep and strengthen it during physical work), and blood vessels can change their lumen and tone depending on the situation. Over the years, most people’s hearts “wear out” and blood vessels become clogged with cholesterol, so the capabilities of the cardiovascular system in many older people are no longer the same as in their youth, and regulatory systems lose their flexibility. Nevertheless, if a person trains his heart and blood vessels throughout his life, they can remain in good condition for a very long time. It is not enough to have a healthy heart muscle and clean blood vessels that are not clogged with “toxins”. In addition, the heart must be properly controlled by the autonomic nervous system, which adapts its rhythm to changing situations. Actually, the heart has its own built‑in rhythm generator, which makes it contract about 75 times per minute (the so-called “rhythm driver”), but it is controlled by special nerve centers that can both slow down and accelerate its work. For example, if a person climbs the stairs to the 5th floor, then the heart should increase its activity in order to deliver more oxygen and nutrients to the muscles, and if the person is asleep, then the heart, on the contrary, should slow down the rhythm. When, with age, due to smoking, malnutrition, a sedentary lifestyle, or for any other reason, the vessels become “clogged” so that their lumen becomes smaller, the heart has to push blood with additional effort ‑ and a person’s blood pressure increases more than necessary. As a result, the risk of rupture of small vessels increases, which can lead to hemorrhages in vital organs. Blockage of blood vessels by blood clots (pieces of clotted blood) can lead to damage to the heart muscle (heart attack) or brain cells (stroke).

If you want to keep your cardiovascular system in good condition for decades, you need to train it and keep it in optimal shape. To do this, you need the following: 1. Aerobic exercises (long rhythmic loads that require increased breathing – running, brisk walking, swimming, skiing, etc.). 2. Emotional state management skills (you need to learn how to cultivate positive emotions and avoid negative ones). 3. Giving up bad habits (completely quitting smoking and reducing the amount of alcohol consumed). 4. Maintaining your weight within certain limits. 5. Periodically giving your body and brain a good rest. Shcherbatykh Yu.V. “How to stay young and live long” Photo: bitrenta.by