The heart
The heart: and so the beat goes on, on and on...
Our heart beats continually, 100,000 times a day, pumping 10,000 litres of blood through our body – day in, day out, every day of our lives. This is an incredible feat when one considers that this happens completely automatically, without any apparent driving force. But what exactly is going on down there?
Our blood circulation system is like a street with a ‘figure of 8’ shape.
If you look at our blood circulation system in this way, the heart (the most important muscle in the body) is at the crossroads of this figure of 8-shaped street. With the heart acting as a pump, blood is transported along “traffic arteries” and blood vessels throughout the entire body. It works like this...
Surrounded by a sac called the pericardium, the heart is divided lengthways by a muscular partition wall (the septum) into one right half and one left half. Each of these halves is further divided into an upper part (atrium) and a lower part (ventricle). These four sections are interlinked by special “doors” called valves, which are responsible for keeping the flow of blood in one direction.
Via the right ventricle, the heart pumps blood flowing back from the body (by now depleted or “used-up” and low in oxygen) into the lungs. Here, the blood absorbs oxygen from inhaled air and returns to the left part of the heart. The blood, now rich in oxygen and bright red as a result, is then pumped via the body’s main artery (aorta) into the circulation. Branching off from the aorta, arteries extend into different areas of blood vessels within the body, thereby supplying our various organs with oxygen-rich blood. In turn, used blood (which is low in oxygen) flows back into the right atrium via our veins. And so, the cycle starts again from scratch. Incidentally, there are certain blood vessels responsible for supplying the heart itself with oxygen-rich blood; these are known as coronary arteries.
How does the heart itself function?
The heart works like a rhythmic pump. Each contraction of the heart muscle is known as systole, whilst each recovery phase or resting period is called diastole. The sinus node is responsible for the regular pumping of the heart. It sends out measurable electrical impulses, which - via a special conduction system - reach all parts of the heart and ensure that they work together in close coordination. This function can be examined by means of an electrocardiogram (ECG).
The pulse rate is also dependent on the number of impulses sent out by the sinus node. Each heartbeat triggers off a shock wave within the body, which can be felt as a pulse in the arteries, particularly at the wrist or carotid artery. On average, the heart beats 60-80 times a minute in adults; in children, this rate is higher. Regarding the overall function of the heart, not only is it important how often the heart beats or how much blood it pumps, but also the pressure at which blood pulsates through the veins. This is known as blood pressure.
To gain a clearer picture, doctors always check two values when measuring blood pressure, i.e. an “upper” and “lower” value. Pressure is at its highest when the heart contracts (systole), as when this happens, the heart forces more blood into the circulation, causing the blood pressure to rise. Hence this “upper” pressure value is also known as ‘systolic blood pressure’. In the resting phase (diastole), pressure decreases once again, earning this “lower” value the title ‘diastolic blood pressure’.