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The heart, blood vessels and blood form the system. cardiovascular or circulatory.
Blood circulation allows the transport and distribution of nutrients, oxygen gas and hormones to the cells of various organs. The blood also carries waste metabolism so it can be eliminated from the body.
A person's heart is about the size of his fist, and pumps blood all over the body, without stopping; It is located inside the thoracic cavity between the two lungs. The apex (tip of the heart) is facing down, left and forward. The average heart weight is approximately 300 grams, varying with the size and gender of the person.
Notice the scheme of the human heart, there are four cavities:
- Right atrium and left atriumat its top;
- Right ventricle and left ventricle, at its bottom.
Blood entering the right atrium passes into the right ventricle and blood entering the left atrium passes into the left ventricle. An atrium does not communicate with the other atrium, just as one ventricle does not communicate with the other ventricle. Blood passes from the right atrium to the right ventricle through the right atrioventricular valve; and passes from the left atrium to the left ventricle through the left atrioventricular valve.
The human heart is a cavity organ (which has a cavity), basically consisting of three layers:
- Pericardium - is the membrane that lines the heart externally, like a sac. This membrane provides a smooth and slippery surface to the heart, facilitating its uninterrupted movement;
- Endocardium - is a membrane that covers the inner surface of the heart cavities;
- Myocardium - is the muscle responsible for the involuntary vigorous contractions of the heart; It lies between the pericardium and the endocardium.
When for some reason the coronary arteries - aortic branches - fail to properly irrigate the myocardium, muscle cell death (necrosis) can occur, which characterizes myocardial infarction.
There are three basic types of blood vessels in our body: arteries, veins and capillaries.