Dorothy FarrarCardiovascular system
The cardiovascular system includes the heart, systemic circulation and pulmonary circulation. Blood takes about 60 seconds to circulate throughout the human body’s bloodstream. The cardiovascular system supplies the organism with vital nutrients and oxygen.
What is the cardiovascular system?
In humans, blood flows in a system of interconnected blood vessels, in a double closed circuit.
The heart pumps blood to all parts of our body. It is a hollow muscle about the size of a fist, which lies behind the breastbone and its tip points diagonally to the lower left.
The heart consists of two halves separated by a cardiac septum. Each half is divided into an atrium and a ventricle.
The valve-like flaps control the flow of blood from the atrium into the corresponding ventricles. The blood flow from the ventricles is regulated by semilunar valves.
In a resting adult, the heart beats 60 to 70 times per minute. With every heartbeat , around 70 ml of blood is pumped from the right ventricle into the pulmonary artery and from the left ventricle into the body artery (aorta).
Functioning of the heart
Our heart works continuously – for a lifetime. Both halves of the heart work simultaneously, with the atria and ventricles alternately contracting (systole) and expanding (diastole). First, the atria contract and deliver blood to the relaxing ventricles. The chambers of the heart then contract and push the blood into the arteries (arteries).
At the same time, the atria expand and thus absorb new blood from the veins. This is followed by a brief rest period of around 0.2 seconds, during which the heart muscle recovers. When the ventricles contract, the flaps close the opening to the atrium, preventing blood from flowing back.
Semilunar valves at the origin of the arteries branching off from the ventricles also prevent blood from flowing back into the expanding ventricles. The heart works like a pump, pressure and suction processes alternate rhythmically with each other.
Vascular system (blood vessels)
The blood vessels include arteries (carotid arteries, wrist arteries), veins and blood capillaries (hair vessels).
arteries
Arteries are blood vessels that carry blood away from the heart. They carry blood to all parts of our body. The artery wall consists of a thick and elastic layer of muscle. Due to the pressure of the inflowing blood, this is stretched and is therefore constantly exposed to great stress.
By contracting the wall muscles of the artery, the artery is pulled together again, pushing the blood a little further. This creates a pressure wave (pulse wave) in the rhythm of the heartbeat, which continues over the entire artery and enables a constant flow of blood.
Blood pressure decreases further away from the heart because the arteries branch more and more. They become thinner and thinner until they finally become hair-thin capillaries and are therefore connected to every cell in our body.
The pressure wave can be felt as a pulse at certain parts of the body (eg on the wrist and neck). Since the pulse wave is originally triggered by the heart muscle contraction, heart activity can be checked by measuring the pulse .
capillaries
Capillaries form a very fine network of very narrow tubes with a very large surface, which runs through all organs and tissues. Nutrient building blocks dissolved in the blood, oxygen, mineral salts , vitamins , enzymes and other active ingredients and supplements diffuse from the capillaries into the adjacent body cells. Metabolic end products (eg carbon dioxide), which are produced in the cell and are very harmful, are released into the blood at this point.
The capillaries are not very stretchy, consist of a cell layer (therefore very thin walls) and thus enable a quick and effective exchange of substances between blood and body cells. The capillaries in turn unite to form veins.
They come
Veins are blood vessels that bring blood back to the heart. They only have to withstand little pressure, their walls consist of a thin layer of muscle, they are thin, not very elastic and cannot actively contract like arteries.
Several devices support the venous blood transport: On the one hand, the veins are often accompanied by arteries, whose pulse activity is transmitted directly to the vein wall and thus supports the transport of venous blood to the heart. On the other hand, the blood is slowly moved towards the heart by the contraction of surrounding muscle groups , since the veins are repeatedly compressed by the muscle activity .
The direction of blood flow to the heart is determined by valves, which are mainly located in the medium-sized veins of the trunk and limbs. These valves = vein valves (pocket-like valves inside the veins) prevent the blood from flowing back. The blood is only additionally sucked in during diastole (relaxation) in the vicinity of the atria of the heart. Finally, the breathing-related pressure fluctuations in the chest cavity exert a rhythmic suction on the veins.
Blood circulation
Humans have a double closed blood circuit. Based on the function, a distinction is made between the small pulmonary and the large systemic circulation. The blood is pressed from the heart to the lungs, back to the heart and then into the body’s vessels. The total of all blood vessels in our body is 100,000 km in an adult. That is twice the circumference of the earth.
Pulmonary circulation
In the pulmonary circulation, the oxygen-poor blood coming from the body is pumped through the right ventricle via the pulmonary artery and then via the smallest branches, the pulmonary capillaries, into the lungs (alveoli). There it is enriched with oxygen and carbon dioxide is released into the air sacs (alveoli). As oxygen-rich blood, it is then transported via the pulmonary vein to the left atrium of the heart. The pulmonary circulation begins in the right ventricle and ends in the left atrium.
Body circulation
In the subsequent systemic circulation, the oxygen-rich blood coming from the lungs is pumped through the left ventricle via the body artery (aorta). The body artery branches into tiny hair-thin blood capillaries that supply all organs with blood rich in oxygen and nutrients and at the same time absorb metabolic end products such as toxic carbon dioxide.
The blood that flows through the capillaries of the villi of the small intestine is enriched with nutrient building blocks at this point and then introduced into the circulatory system. The blood, enriched with waste and pollutants, passes through small branched veins to the large vena cava in the right atrium of the heart and finally into the right ventricle. From here it is reintroduced into the pulmonary circulation. The systemic circulation begins in the left ventricle and ends in the right atrium.
Cardiovascular diseases
Training of the cardiovascular system
In the pulmonary circulation, the blood in the lungs is enriched with oxygen and gives off carbon dioxide. In the systemic circulation, the blood delivers oxygen to the cells and is enriched with carbon dioxide and nutrient building blocks.
The muscle layer of the left ventricle is about three times as thick as that of the right ventricle due to the different demands.
Since the systemic circulation is much more extensive, it needs a stronger and more powerful pump (left ventricle) to transport the blood through the vascular labyrinth without any problems.
With regular physical exertion ( endurance training ), the heart muscle cells enlarge so that the heart can contract more strongly. Heart rate decreases and stroke volume increases.
The heart works more effectively and efficiently under these conditions. In addition, it is better supplied with blood at a lower frequency, and therefore better supplied with nutrients and oxygen, since it has longer rest periods.
Daily training , in which the body is required to perform at around 50-75% of its capacity for at least 10 minutes (130-150 pulse beats per minute), makes a significant contribution to keeping the heart healthy. Suitable sports would include jogging , cycling, swimming or other endurance sports .
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.