Blood circulation

The bloodstream is the closed vascular system in which the blood is pumped from the heart through the body. Read more about structure and problems here!

Blood circulation

Of the blood circulation is the closed vascular system in which blood is pumped from the heart through the body. The blood brings oxygen and nutrients to the body cells and transports waste products such as carbon dioxide. There are two successive circuits, the large circulatory system (circulatory system) and the small circulatory system (pulmonary circulation). Read all important information about the blood circulation!

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blood circulation

  • What is the blood circulation?

  • What is the role of the circulatory system?

  • How is the blood circulation regulated?

  • What problems can the bloodstream cause?

What is the blood circulation?

The blood circulation is a self-contained vascular system with supply and disposal function. All body cells must be supplied with vital substances such as oxygen (bound to the red blood pigment hemoglobin), nutrients, vitamins and minerals. By contrast, waste products (such as carbon dioxide) are transported away from the tissue by the blood. In addition, messenger substances (such as hormones) and defense cells of the immune system circulate in the blood.

The blood is driven by the heart. The powerful hollow muscle pumps blood through the blood vessels day and night, thus keeping the blood circulation going. Heart and vascular system together make up the cardiovascular system.

Low pressure system and high pressure system

A distinction is made in the blood circulation of humans, a low-pressure system and a high-pressure system. In the low-pressure system, the mean blood pressure is no more than 20 millimeters of mercury (mmHg). This vascular section includes all veins and capillaries, the pulmonary vessels, the right atrium and the right ventricle, the left atrium, and during diastole also the left ventricle. The low-pressure system contains about 85 percent of the total blood volume.

In the high pressure system - consisting of the left ventricle during systole and all arteries (including aorta and arterioles) - there is a much higher blood pressure: it varies between about 80 mmHg (during diastole) and 120 mmHg (during systole). The high pressure system houses about 15 percent of the total blood volume.

Small and big blood circulation

The circulatory system is made up of two interconnected circuits: the large circulatory system or the systemic circulation and the small circulatory or pulmonary circulation.

The large bloodstream or systemic circulation begins in the left ventricle, which pumps the high-oxygen-rich blood into the aorta (main artery). Via the aorta and its branches (arteries, arterioles) the blood reaches the finest vessels, which at the same time represent the transition to the venous system - the capillaries. Through its thin wall, the mass transfer (oxygen, nutrients, waste products such as carbon dioxide, etc.) takes place between the tissue and the bloodstream. The now low-oxygen and carbon dioxide-laden blood then returns via the veins to the heart, into the right half of the heart. There begins the small blood circulation or pulmonary circulation.

What is the role of the circulatory system?

The most important task of the blood circulation is the distribution and removal of nutrients, messengers and gases. For more information, see the following texts:

Pulmonary circulation

Everything important about the small blood circulation read in the article pulmonary circulation.

portal circulation

A special cycle section is the venous circulation, which transports the blood from the digestive tract via the liver to the inferior vena cava. You can read more about this in the article Pfortaderkreislauf.

How and where can you feel your pulse? And what should be considered when measuring the heart rate?

How is the blood circulation regulated?

Blood circulation or blood pressure is regulated by different mechanisms involving, among others, the autonomic nervous system and hormones.

A short-term regulation is possible about circulatory reflexes. This involves various sensors, such as pressure receptors (baroreceptors) in the vessel walls, which measure the prevailing blood pressure. The main baroreceptors sit in the wall of the aortic arch and carotid sinus. As the blood pressure increases, the vessel walls are stretched, which excites the baroreceptors. They pass on the information about nerves to the brain, which can then counteract by activating the parasympathetic nervous system: This part of the autonomic nervous system ensures, among other things, that the heart beats slower and blood vessels widen. As a result, the blood pressure drops.

Conversely, a drop in blood pressure is also registered by sensors and reported to the brain. Through activation of the sympathetic heart rate increases, and the vessels narrow - the blood pressure rises again.

Important sensors for blood pressure regulation also sit in the kidneys. They register it when the blood supply to the kidneys decreases.As a result, the neurotransmitter Renin is increasingly released, which in turn ensures the release of angiotensin II. This hormone causes the vessels to contract, pushing up the blood pressure.

In the long term, the blood circulation or blood pressure can be controlled via the water and electrolyte balance. With increased blood pressure, the body can increasingly excrete water through the kidneys and thus reduce the blood volume - the blood pressure drops. If the blood pressure is too low, the kidneys can increasingly retain water in the body to increase the blood volume and thus the blood pressure again.

What problems can the bloodstream cause?

High blood pressure (arterial hypertension) is a major burden for the heart and circulation: For those affected, the blood pressure is 140/90 mmHg or more over a longer period of time. Without treatment, this damages the heart and vessels.

If the first (systolic) blood pressure value is below 100 mmHg, hypertension is present (low blood pressure). This only has a medical effect if the person concerned shows symptoms such as a reduced ability to perform, an impaired ability to concentrate or cold hands and feet.

In some people, rapid sitting up from a lying or sitting position leads to a sudden drop in blood pressure (orthostatic hypotension): those affected are dizzy, they have tinnitus and a flicker in front of their eyes. Other symptoms such as heart palpitations, sweating and paleness to a circulatory collapse and syncope are possible.

Another health problem in the area of Blood circulation is the shock. This refers to a circulatory failure with critical reduced blood flow of organs. The cause can be for example a large blood loss (hypovolemic shock) or a pumping failure of the heart (cardiogenic shock). Another possibility is a severe allergic reaction of the immediate type, which leads to a failure of the blood circulationRegulation leads (anaphylactic shock).

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