Lymphatic system

Lymphatic system – a complex of the vessels, which carry with lymph from tissue fluid into the blood stream electrolytes, water, proteins, etc. the Lymphatic system consists of branched organs and tissues lymphatic capillaries (lymphoepithelial), impacability networks, lymphatic vessels, trunks and ducts. Along the route of lymphatic vessels lie lymph nodes related to the immune system. Lymph is absorbed into the lymph capillaries and enters the lymph vessels, which have special valves that prevent the reverse flow of lymph. The lymphatic system consists of two large collectors – the thoracic duct and the right lymphatic duct, through which the lymph returns to the bloodstream (the thoracic duct flows into the left venous angle, the right lymphatic duct – into the right venous angle, formed by the merger of the internal jugular and subclavian veins).

Lymph is formed from tissue fluid, it contains about 20 g / l protein. During the day, an adult produces about 2 liters of lymph. The rate of lymph flow is small, but it increases by 10-15 times during exercise, because it is muscle contractions that mainly contribute to the movement of the lymph.

The function of the cardiovascular system

Myocardium is striated muscle tissue. Like all muscle tissues, myocardium has three important properties: irritability, excitability and contractility. The basis of all physiological reactions is irritability – the ability of a living cell to respond to an irritant. An irritant is any factor of the external or internal environment, which acting on the living structure (cell, tissue, organ, body) can cause its active reaction. Excitability-the ability to actively respond to irritation by generating an electric pulse that is transmitted over different distances. Contractility-the ability to reduce (to reduce the length of the fibers) and to do the work when reducing.

Since childhood, most men remember a simple experiment-an isolated (taken out of the body) frog heart can shrink for a long time without nerve impulse in the presence of oxygen and nutrients. Why? The heart has another important property-automatism (from the Greek. automatos-self-acting, spontaneous). This is due to the Autonomous conductive system of the heart, one of the elements of which generates a nerve impulse.

Conducting atrioventricular system of the heart consists of the sinus node (kitty – FLAC), which is the pacemaker (pejjsmeker), atrioventricular node (Asifa – Tawara), atrioventricular bundle (bundle branch block), his legs and branches (Purkinje fibers). Conducting system of the heart is formed by the conductive fibers are richly innervated by nerves of the autonomic nervous system. Atria are interconnected by a sinus-atrial node, and Atria and ventricles-atrioventricular bundle (Fig. 20 per cent. insert.) The sinus-atrial node generates 60-70 pulses per minute, which cause atrial contractions, the pulses are transmitted to the atrioventricular node, from it to the atrioventricular bundle, then to its legs, branching and ventricular myocardium. Myocardium is Contracting rhythmically.

The frequency, speed of the pulse and the force of contractions are regulated by the autonomic nervous system. Sympathetic nerves have a positive effect (increased heart rate and increase their strength), parasympathetic – negative (reduction of heart rate and decrease their strength). The cerebral cortex regulates the activity of the heart centers through the hypothalamus.

Contraction of the heart muscle provides the pumping function of the heart. The movement of blood through the vessels is mainly due to the injection function of the heart and the reduction of skeletal muscles. The heart is a pump that pumps blood into the blood vessels.

As shown by modern studies, each striated muscle fiber is a kind of” peripheral heart”, the reduction of which contributes to the promotion of blood in the microcirculatory bed. Muscles, Contracting, contribute to the movement of blood through the veins of the lower half of the body against gravity. Therefore, physical activity facilitates the work of the heart, and hypodynamia requires increased work of the heart, which is one of the important factors of violation of its function.

In the work of the heart alternate contraction (systole) and relaxation (diastole). During the General relaxation of the heart (diastole), blood from the hollow and pulmonary veins enters the right and left Atria, respectively. After this comes the reduction (systole) of the Atria. The process of contraction begins at the confluence of the superior Vena cava in the right atrium and spreads through both Atria, resulting in blood from the Atria through the atrioventricular orifices is pumped into the ventricles. Then a wave of ventricular contractions begins in the walls of the heart, which extends to both ventricles, and blood is pumped into the holes of the pulmonary trunk and aorta, at this time the atrioventricular valves are closed. After that comes the pause. Atrial systole lasts 0.1 s, ventricular systole-0.3 s, the total pause-0.4 s. These three phases make up the heart cycle-a set of processes occurring in the heart during one full cycle of contraction and relaxation. Thus, during one cardiac cycle, the Atria are reduced by 0.1 s and rest by 0.7 s; the ventricles are 0.3 and 0.5 s, respectively. During the day, the heart is reduced 8 hours and 16 hours rest.

Due to changes in pressure in the heart, the valves of the heart, pulmonary artery and aorta are opened or closed. At the beginning of the ventricular systole, the atrioventricular valves close and the semilunar valves of the aorta and pulmonary artery open. In the period of diastole ventricular systole occurs, the Atria, the atrioventricular valves open, ventricles fill with blood. The return of blood from the aorta and pulmonary trunk is prevented by semilunar valves.

Heart rate per minute is at the age of 1 year, about 125 beats/min, a 2 year – 105 in 3 years – 100, 4 – 97, ranging in age from 5 to 10-90, with 10 to 15-75-78, from 15 to 50-70, with 50 to 60-74, from 60 to 80-80 beats/min. Some interesting figures: during the day the heart beats about 108 000 times, during the life – 2,8–3,1 billion times; the heart is 225-250 million liters of blood.

The heart adapts to the ever-changing conditions of human life. At rest, the ventricles of an adult are pushed into the vascular system about 5 liters of blood per minute. This indicator – the minute volume of blood circulation (IOC) – with heavy physical work increases 5-6 times. The ratio between the IOC at rest and with the most intense muscle work speaks about the functional reserves of the heart, and therefore about the functional reserves of health. Adequate physical activity ensures optimal functioning of the cardiovascular system and high functional reserves of the heart. At the same time, blood flow through the vessels of the heart reaches 5% of the total IOC. Under intense physical work this figure increases in 3-4 times. The amount of blood released by each ventricle during systole ranges from 70 to 100 ml-a shock, or systolic, blood volume. This figure also increases with exercise.

The average weight of the heart of an adult is 300-320 g (0.5% body weight), while at rest the heart consumes about 25-30 ml 02 per minute – about 10% of the total consumption of 02 at rest. With intensive muscle activity, the consumption of 02 by the heart increases 3-4 times. Depending on the load, the efficiency of the heart is from 15 to 40 %. The efficiency of modern diesel locomotive reaches 14-15 %. The human heart works more efficiently than a locomotive!

The bioelectric activity of the heart is recorded by electrocardiography, the resulting curve is called an electrocardiogram (ECG). The first electrocardiogram was recorded in 1887 by G. A. Waller. At the beginning of the XX century, V. Einthoven developed a device for accurate registration of small fluctuations in electrical potentials – a string galvanometer. Einthoven also proposed three points of the body on which electrodes should be applied. In 1924, Einthoven was awarded the Nobel prize”for the discovery of the mechanism of electrocardiogram.” A normal ECG consists of several teeth and of the complex of vibrations which Einthoven called P, QRS and T. the Small prong R reflects the electrical activity of the Atria, and rapid high-amplitude QRS complex and slower the T wave is the electrical activity of the ventricles.

So, blood flows from the high-pressure area to the low-pressure area. Blood pressure (BP) is the pressure developed by the blood in the arteries. This is the most important indicator reflecting the activity of the cardiovascular system as a whole. The stability of blood PRESSURE is supported by many mechanisms of homeostasis. The maximum pressure during systole is called systolic pressure, the minimum during diastole is diastolic pressure, the difference between them is pulse pressure. In humans, traditionally, blood PRESSURE is investigated using a mercury manometer, so it is expressed in millimeters of mercury (currently, there are many modifications of devices for determining blood PRESSURE). To measure blood PRESSURE, the lower third of the shoulder is wrapped with an inflatable rubber cuff of the device, into which air is pumped with a hand-held rubber pear. To release the air is a valve, so you can set the pressure at any level and measure it with a pressure gauge connected to the cuff. A stethoscope placed on the skin of the front of the elbow region in the zone of passage of the brachial artery. As a result of air injection into the cuff, the brachial artery is compressed. Then slowly open the valve, the air begins to come out of it, and so the pressure in the cuff decreases. When it falls below sistolicheskogo, the blood passes through the artery, and begin to listen short clear sounds, pulse beats is determined by sistolicheskoe pressure. The pressure in the cuff, in which the sounds of pulse strokes disappear again quickly, corresponds to diastolic (Fig. 21 per cent. insert.) In a person aged 20 to 40 years systolic pressure is 100-120 mm Hg. art., diastolic 70-80 mm Hg. art.

Blood flow fluctuations associated with systole and diastole create a pulse wave. The heart rate (pulse) in an adult at rest is from 60 to 80 beats per minute. The pulse is studied by simply probing the radial artery in the region of the wrist joint, while paying attention to the pulse frequency, its rhythm (rhythmic, arrhythmic), height (high, low), tension (hard, soft). The pulse rate of a person depends on physical work and emotional state, height – on the shock volume, tension – on blood pressure. The total volume of blood in human vessels in men averages 75-77 ml/kg body weight (about 5.4 l), in women – 65 ml/kg (about 4.5 l). In an adult, only about 9% of all blood is in the vessels of the small circle of blood circulation, about 84% – in the vessels of the large circle of blood circulation and about 7% – in the cavities of the heart.

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