The Heart

The heart is a muscularorgan found in all animals with a circulatory system (including all vertebrates), that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions.

The vertebrate heart is composed of cardiac muscle, which is an involuntary striated muscle tissue found only in this organ, and connective tissue. The average human heart, beating at 75 beats per minute. Resting cardiac output 5.25 L/min. At rest Stroke volume normally 60.00 ml.

The heart is an autorythmic structure that is able, by the help of the autorhythimc fiber, to excite itselfin order to contract. It has the system of blood flow, the pulmonary circulation, systemic circulation and coronary circulation.

The heart moves in a very systematic procedure, it has the processes of systole and diastole, and these processes divides according to the atrial and ventricular parts of the heart. Thus it achieves the ability to fill itself with blood thus increasing the pressure to send to the lung the deoxygenated blood receive the oxygenated blood through diffusion of CO2 and O2, and once more fill itself to gain pressure enough for transmitting the blood to the aorta, thus the entirecirculatory system. Also a very important aspect of the heart is its ability to supply itself with oxygenated blood and to re-oxygenate it deoxygenated blood. Thus it is a fully capable to run itself and supply itself alone.

Part 2 The Blood vessels

The blood vessels are the part of the circulatory system that transports blood throughout the body. They contribute to homeostasis by providing the structures for blood flow to & from the heart and the exchange of nutrients & wastes in tissues. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart.

Aorta is the main artery of the body from which all others derive. It arises from the left ventricle arches over the top of the heart and descends in front of the backbone, giving off large and small branches finally dividing to form right and liliac arteries. All arteries except pulmonary artery carry oxygenated blood. The walls of the arteries contain smooth muscle fibers, which contract or relax under the control of the sympathetic nervous system. Arteriole is a small branch of an artery leading into many smaller vessels- the capillary. By their constriction and dilation, under the regulation of the sympathetic nervous system, arterioles are the principle controllers of blood flow and pressure.

Vein a blood vessels conveying blood towards the heart. All veins except the pulmonary vein carry deoxygenated blood from the tissues, via the capillaries to the vena cava. Vein is much thinner and less elastic than

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