Link to the lesson

The build of the heart

Cardiovascular system is a closed transporting system, which is composed of the heart and blood vessels. HeartheartHeart has the shape of a cone and the size of a closed fist. It is found in the middle of the chest, behind the sternum, and its tip is pointed to the left. It is composed of striated muscle tissue, which contracts regularly, forcing the blood to flow in blood vessels. There are 4 chambers of the heart: 2 atriaatriumatria (right and left) and 2 ventriclesventricleventricles (right and left). There are walls between particular parts of the heart. The walls of the ventricles are thicker and more muscular than the walls of the atria. This happens because the atria transport the blood only to the ventricles, and the ventricles transport it into all the arteries. The pressure of the blood pushed out by the ventricles must be this high in order for the blood to reach even the cells that are located the furthest from the heart. VeinsveinsVeins enter into the atria and transport blood into the heart, whereas arteriesarteriesarteries start from the ventricles and they transport the blood from the heart. Between the atria and the ventricles and at the place where the vessels exit the ventricles there are valvesvalvevalves. They open in one direction only, which means they force the blood to flow in one direction and prevent it from regressing.

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Rysunek przedstawia schemat budowy serca. Mięsień (jaśniejsze ściany, ciemniejsze wnętrze) leży ukosem. Białe strzałki wskazują kierunek przepływu krwi. Do prawego przedsionka, right vestibule wchodzi z góry błękitna żyła główna górna, main upper vein z dołu żyła główna dolna, the lower main vein. Między przedsionkiem a komorą znajduje się zastawka, valve. Z prawej komory, right ventricles krew wpływa do niebieskiej tętnicy płucnej, pulmonary artery rozgałęziającej się w kształcie litery T. Do lewego przedsionka dochodzi pomarańczowa żyła płucna, pulmonary vein. Z lewej komory, left vestibule krew wpływa do czerwonej aorty, aorta. Pomiędzy przedsionkami, vestibules znajduje się przegroda przedsionkowa, atrial septum. Pomiędzy komorami znajduje się przegroda komorowa, intraventricular septum.

In order to describe how heart works using a schematic drawing, we must first establish, which part is left and which part is right. In order to do this, we put the piece of paper with the schematic drawing of a heart to our own torso, as if we wanted to show the model of our own heart. The parts of the schematic drawing of the heart on our left side are the left ventricle and left atrium, and those on our right side – right ventricle and right atrium.

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Ilustracja przedstawia sylwetkę torsu człowieka. Oznaczono na środku klatki piersiowej jaskrawo czerwone serce. Koniuszek serca skierowany w bok. Na sercu rozgałęzienia, czyli tętnice wieńcowe, Coronary arteries. U góry i za sercem grube naczynia krwionośne: niebieskie żyły, czerwone tętnice.

How the heart works

If blood isn’t reaching an organ for several minutes, that place suffers from irreversible changes and necrosis of tissues, which is why the heart beats non‑stop. Heart beat is composed of contractions of the organ, one after the other. A doctor listens to cardiac cycle when putting stethoscope to our chest. He pays attention e.g. to the tones, which approximately are identical with contractions of the ventricles and them unflexing.

First, blood transported by the veins fills both atria. When the atria contract, they push blood into the chambers. Then, both ventricles contract, pushing the blood from the heart into the arteries. After that, heart has a short period of rest. When it is relaxed, the atria become filled with blood again.

The heart contracts between 60 and 80 times per minute, pushing around 80 cmIndeks górny 3³ of blood during every contraction. The pressure of the blood flowing from the heart can be felt in the arteries as pulsepulsepulse and measured with a blood‑pressure device. This device shows you the values of systolic pressuresystolic pressuresystolic pressure (120 mm Hg) and diastolic pressurediastolic pressurediastolic pressure (80 mm Hg). Blood pressure is measured during rest, because it becomes elevated during effort. The values of the pressure can change, depending on the physical activity, emotional state, temperature and food that we consumed.

Contracting heart works, which is why it requires large amounts of energy. This is why it has its own network of blood vessels called coronary arteries. They provide each cell of the heart muscle with elements necessary for cellular respiration. Cardiac cycle does not depend on us. The heart has a natural pacemaker, composed of highly specialized cells, which have the ability to move the heart muscle and make it contract.

Observation 2

Searching for arteries and measuring the pulse.

You will need

• you,

• a stopwatch.

Instruction

1. Sit comfortably. Using your index and middle fingers of the right hand search on the left side of the trachea for the carotid artery.

2. Feel the pulse with your fingers. Count pulse during 30 seconds, multiply the result by 2.

3. With your index finger and middle finger try to find the pulse on the radial artery above the wrist on the thumb side. Measure the pulse, the result is expressed in the number of beats per minute.

4. Compare the results.

5. Learn how to feel the pulse on the radial arteries of your classmates.

6. Explain, in which situation you can use this skill.

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Zdjęcie przedstawiające sposób pomiaru tętna. Na pierwszym obrazku kobieta przykłada dwa palce do tętnicy szyjnej lekko ją uciskając, tak by wyczuć puls. Jednocześnie spogląda na zegarek na drugiej ręce. Na drugim obrazku kobieta przykłada dwa palce do tętnic nadgarstka drugiej ręki. Lekko uciska tętnicę by wyczuć puls.

Summary

Pulse is the rhythm in which blood is moved into the arteries by the left ventricle, it basically equals the frequency of the contractions of that ventricle. Arteries are usually hidden between tissues which give them protection against injuries and pressure.

Summary

• Cardiovascular system includes the heart and blood vessels: Veins, arteries and capillaries.

• Heart is the suction and forcing pump, that makes the blood move in the vessels.

• Human heart is divided into 4 parts: 2 atria and 2 ventricles.

• Valves that are present in the heart and in veins force the blood to flow in one direction only.

• Arteries lead blood from the heart, whereas veins lead blood to the heart.

• Capillaries are wrapped around cells, provide them with nutrients and participate in gas exchange.

Keywords

heart, valves, aorta

Glossary