2.3 The heart and circulatory system
The engine of the circulatory system is the heart; it has the function of a pump that propels the blood in the vessels. The heart is an organ that works automatically, i.e. the electrical impulses that lead to the contraction of the heart muscles and thus to the heart work arise in an excitation center in the heart itself, in the area of the right atrium. However, the work of the heart is influenced by the autonomic nervous system and by hormones (changes in pulse rate and contraction force) depending on the body load.
In response to the electrical impulse from the arousal center, the muscles in the atria first contract and force the blood into the ventricles. 0.1~~0.2 seconds later, the excitation also reaches the musculature of the two heart chambers via a special power system, which eject the blood into the pulmonary artery and the body artery.
The used blood coming from the systemic circulation flows from an upper and a lower large vena cava into the right atrium. The blood is transported through a valve to the right ventricle. The valves on the heart have the task of a valve, which only allows blood to flow in one direction (atrium-ventricle, ventricle-artery). When the right ventricle contracts, blood is ejected—again through a valve—into the pulmonary artery. This is divided into the pulmonary vessels up to the hair vessels (capillaries), which surround the alveoli. This is where the gas exchange of °2 and CO₂ takes place . The pulmonary vessels then unite again and the oxygen-rich blood reaches the left atrium via the pulmonary vein.
The blood passes through another valve from the left atrium into the left ventricle, which squeezes the blood into the large artery (aorta) when it contracts; The blood also has to pass through a heart valve between the left ventricle and the aorta.
The path of blood from the right heart through the pulmonary vessels to the left heart is called the minor or pulmonary circulation, that from the left heart through all the vessels of the body back to the right heart is called the major or systemic circulation.
Right at the beginning, the coronary arteries branch off from the large aorta to supply the heart muscle, followed by the arteries for the right arm, the head, the left arm, the abdominal organs, the organs of the pelvis and finally for the legs. The arteries branch into smaller and smaller branches up to the hair vessels (capillaries). There, the oxygen is released from the blood to the tissue and carbon dioxide is absorbed.
The vessels then unite again to form the veins, which become increasingly thick towards the center and which finally lead the blood back to the heart as the upper and lower large vena cava.
A distinction is made between blood vessels:
Arteries (arteries), which lead away from the heart and allow the pulse to be felt,
blood vessels (veins), which return the blood to the heart,
capillaries (capillaries), which form a network between arteries and veins and in which gas exchange takes place.
2.4 Breathing
Respiration is used to absorb oxygen (°2), which the organism needs to generate energy, and to release carbon dioxide (CO₂), which is the end product of the "combustion" of food.
The processes of energy generation using oxygen (°2) and the release of carbon dioxide (CO₂) in the cell are referred to as internal respiration .
The gas exchange in the lungs is called external respiration .
The lungs are preceded by the upper airways . This includes:
Noses, mouth, pharynx, larynx, trachea, main bronchi for the two lungs .
The outside air is humidified, heated and cleaned in the upper airways. The main bronchi branch into lobar bronchi, which, after further branching into smaller and smaller bronchial branches, finally end in the alveoli . The pulmonary sacs (alveoli) arranged in a grape-like manner are surrounded by a network of the finest blood vessels (hair vessels or capillaries). The thickness of the layer between the blood in the capillaries and the air in the alveoli is so thin here (less than 1/1,000 mm) that °2 can pass into the blood and CO. into the interior of the alveoli.
The inhaled air contains around 21% °2 and 0.04% CO₂, and the exhaled air contains approx. 17% °2 and 4% CO₂. The body absorbs around 4% °2 of the outside air and releases 4% CO₂. These values change under load.
The two lungs are protected by the ribs and are located in the chest, they are separated from the abdomen by the diaphragm. Air is inhaled by tensing the intercostal muscles. This leads to a lifting of the ribs and thus to an expansion of the thorax in depth and width diameter. The simultaneous flattening of the diaphragm causes a further enlargement of the thorax downwards. This enlargement of the thoracic cavity creates a negative pressure in the thorax, which is compensated for by the air flowing in via the airways supplying it. The inhaled air fills the afferent airways and the alveoli; gas exchange can take place.
Exhalation occurs under resting conditions by passive lowering of the ribs when the inspiratory muscles relax and by contraction of the elastic elements in the lung tissue. With increased exhalation, special exhalation muscles are also activated.
2.5 The blood
2.5.1 Tasks of the blood
The blood primarily assumes the function of a transport system in the body. Its primary tasks are:
— transport of oxygen and carbon dioxide
— transport of nutrients and metabolites
— maintenance of the acid balance and mineral metabolism
— transport of cells and proteins for the body’s defenses
— transport of hormones and other active substances (medicines).
2.5.2 Constituents of blood
The blood consists of 55-60% blood fluid (plasma) in which, among other things, protein molecules, salts, nutrients and hormones are dissolved;
40-45% from blood cells, from which one distinguishes:
— red blood cells (erythrocytes), task: transport of °2 and CO₂,
— white blood cells (leukocytes), task: defense against infection,
— blood platelets (thrombocytes)
2.5.3 Task of blood coagulation
In the area of the alveoli, oxygen enters the blood from the inhaled air in the blood, the oxygen attaches itself to the red blood cells, which are carriers of the red blood pigment hemoglobin . Oxygen forms a loose chemical compound with this hemoglobin, whereby the hemoglobin takes on a bright red colour, that of fresh arterial blood.
In the organs and tissues that need oxygen for their metabolism , there is less oxygen than in the blood. The binding to the hemoglobin is broken, the oxygen passes from the blood into the tissue.
The opposite is the path of carbon dioxide. It is produced during tissue metabolism and is absorbed by the blood, e.g. T. bound to hemoglobin, e.g. T. dissolved in the blood fluid and excreted in the lungs from the capillaries into the alveoli and exhaled.
Dizziness or states of collapse after intense physical activity (middle and long-distance running) are more likely to cause injury from a fall than a real danger in and of themselves. They usually occur as a result of the rapidly falling blood pressure after stress due to a lack of blood and thus a lack of oxygen supply to the brain. To avoid such incidents, athletes should definitely keep moving after intense exertion.
In the event of a collapse, the shock positioning (head down, legs up) should be carried out. A subsequent medical examination must always take place.
However, the possibility of real damage to the heart from sports is present in the following cases:
1.) In the case of congenital or acquired heart valve defects or other anatomical changes in the cardiovascular system that put increased strain on a part of the heart,
2.) in the case of constriction of the coronary arteries with reduced oxygen supply to the heart muscle under stress conditions,
3.) in the case of increased blood pressure, which already exceeds the Increased stress on the heart muscle,
4.) in all inflammatory diseases of the organism (febrile infections, tonsillitis!) during and after the illness (1 to 2 weeks). In this case, a doctor should decide.
2.3 The heart and circulatory system
The motor of the circulatory system is the heart ; it has the function of a pump that propels the blood in the vessels. The heart consists of muscles that enclose two atria and two ventricles; the heart is therefore also referred to as a hollow muscle . The heart is an organ that works automatically, ie the electrical impulses that lead to the contraction of the heart muscles and thus to the work of the heart, arise in an excitation center in the heart itself, in the area of the right atrium. However, the work of the heart is influenced by the autonomic nervous system and by hormones (changes in pulse rate and contraction strength) depending on the body load.
In response to the electrical impulse from the arousal center, the muscles in the atria first contract and force the blood into the ventricles. 0.1~~0.2 seconds later, the excitation also reaches the musculature of the two heart chambers via a special power system, which eject the blood into the pulmonary artery and the body artery.
The used blood coming from the systemic circulation flows from an upper and a lower large vena cava into the right atrium. The blood is transported through a valve to the right ventricle. The valves on the heart have the task of a valve, which only allows blood to flow in one direction (atrium-ventricle, ventricle - artery ). When the right ventricle contracts, blood is ejected—again through a valve—into the pulmonary artery. This is divided into the pulmonary vessels up to the hair vessels (capillaries) which form the alveolisurround. This is where the gas exchange of °2 and CO₂ takes place (No. 327). The pulmonary vessels then unite again and the oxygen-rich blood reaches the left atrium via the pulmonary vein .
The blood flows from the left atrium into the left ventricle through another valve, which squeezes the blood into the large artery (aorta) when it contracts ; The blood also has to pass through a heart valve between the left ventricle and the aorta. The path of blood from the right heart through the pulmonary vessels to the left heart is called the minor or pulmonary circulation, that from the left heart through all the vessels of the body back to the right heart is called the major or systemic circulation .
Right at the beginning, the coronary arteries branch off from the large body artery to supply the heart muscle, followed by the arteries for the right arm, the head, the left arm, the abdominal organs, the organs of the pelvis and finally for the legs. The arteries branch into smaller and smaller branches up to the hair vessels (capillaries). There, the oxygen is released from the blood to the tissue and carbon dioxide is absorbed.
The vessels then unite again to form the veins, which become increasingly thick towards the center and which finally lead the blood back to the heart as the upper and lower large vena cava.
A distinction is made between blood vessels:
Arteries (arteries), which lead away from the heart and allow the pulse to be felt, blood vessels ( veins ), which return the blood to the heart, capillaries (capillaries), which form a network between arteries and veins and in which gas exchange takes place.