How do pulse and blood pressure differ?

Circulation, pulse and blood pressure measurement

Blood flows - with a lot of pressure and in a circle

The Babylonians already knew about 2000 years before our era that blood flows through the body in veins or vessels. When cutting up food or sacrificial animals, they also made a distinction between light and dark blood, which they called "blood of the day" and "blood of night".

In Europe, on the other hand, as late as the 16th century, people insisted on the idea that blood was completely used up on its way through the body. The liver should constantly produce new blood from food components.

At the beginning of the 17th century, the English doctor William Harvey calculated that no human being could ingest and digest as much food as needed to constantly renew the total amount of blood. He found that the blood is not used up in the body, but keeps coming back to the heart. The blood circulates through the body.

A contemporary of Harvey, the English physician Lower, also found that the color of the blood in the lungs changed from dark to light. This change in color is caused by the connection between the blood and the oxygen in the air in the lungs.

Oxygen is vital for every single cell in the body. In order for the blood to reach all of the body's cells, it has to be pumped through the veins at a certain pressure. The heart takes on this task. In a resting adult, it beats about 70 times a minute.

With each heartbeat, around 80 milliliters of blood are pumped into the main artery. That is just under five liters of blood per minute or around 10,000 liters in a day.

100,000 km long conduction pathways - the blood vessels

In addition to an efficient heart, the blood vessels are also of great importance for a functioning blood circulation. With a total length of around 100,000 kilometers, they run through the human body.

The heart pumps blood into the blood vessels. When the heart contracts (the so-called tension phase or systole), the blood is pressed into the large vessels leading away from the heart, the arteries. The arteries have to withstand this direct pressure wave. Its wall consists of a strong muscle layer that is located between the inner and outer skin of the blood vessels.

When the heart presses blood into the artery, the vessel wall is briefly stretched. Immediately afterwards it contracts again and thus drives the blood on. In this way, the blood flow is maintained even in the subsequent relaxation phase of the heart (diastole).

The further the blood moves away from the heart on its way through the body, the weaker the pressure becomes. In the smallest blood vessels, the capillaries, the blood pressure has finally almost completely disappeared. The return of the blood to the heart must therefore take place with very low blood pressure and also against gravity. This is made possible by the so-called muscle pump.

The muscle pump supports the transport of blood in the veins, the large blood vessels that lead to the heart. Veins have a much thinner vessel wall than arteries. In them, the blood is transported through the contraction of adjacent muscles. These muscles compress the veins.

In addition, the veins have pocket flaps that prevent the blood from flowing back. If these valves no longer function properly, the direction of blood flow is reversed. This leads to blood congestion and dilatation of the veins, which then become visible as varicose veins.

The pulse - blood transport can be felt

Unlike breathing, we cannot observe, feel or control the transport of blood through our body. But there are measured values ​​that give us information about the transport of the blood: heart rate and blood pressure. Doctors refer to the number of heartbeats per minute as the heart rate.

The heart rate can be easily measured by feeling the pulse. The pulse is the rhythmic expansion of the arteries as the heart pushes blood into the arteries in spurts. It can be easily felt on the inside of the forearm, near the wrist. On average, a healthy young person at rest has a heart rate of around 70 beats per minute.

Blood pressure and blood pressure measurement

Blood pressure is the pressure with which the arterial wall is stretched. In 1896, the Italian doctor Scipione Riva-Rocci invented a simple method of measuring blood pressure using an inflatable cuff and a column of mercury.

Even today, blood pressure is usually given in millimeters of mercury (mmHg), although the current measure of pressure is kilopascals (kPa). For example, a blood pressure value of 120 mmHg means that the pressure is sufficient to force the mercury in a column 120 millimeters upwards.

First, the cuff is placed on the upper arm and inflated until the artery in the upper arm no longer lets blood through. No pulse can then be detected below the cuff. By releasing the air there comes a point at which the heart can push blood into the artery again in spurts.

The pressure at this point is the systolic blood pressure, which is the result of the contraction of the heart. The systolic pressure gives the higher of the two blood pressure values.

The cuff is gradually deflated until the blood flows freely through the artery and the pulse beats below the cuff disappear. This blood pressure is the lower blood pressure or diastolic value.

According to the German Hypertension League and the World Health Organization (WHO), the optimal blood pressure is a systolic value of 120 mmHg and a diastolic value of 80 mmHg. Doctors speak of high blood pressure from 140 mmHg to 90 mmHg. Permanently high blood pressure can lead to serious cardiovascular diseases.