Heart in The Sky Wallpaper 2560X1600
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|Description:||Heart in The Sky Wallpaper 2560X1600|
|Category||LOVE AND FRIENDSHIP WALLPAPERS|
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|Last view date||17.09.2014 10:08|
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The heart is a muscular organ in humans and many other animals, which pumps blood through the blood vessels of the circulatory system. The blood provides the body with oxygen and nutrients, as well as removing metabolic waste. The heart is located in the middle compartment (mediastinum) of the chest.
The heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Blood normally flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount fluid. The wall of the heart is made up of three layers: epicardium; myocardium; and endocardium.
The heart pumps blood through both circulatory systems. Blood low in oxygen from the systemic circulation enters the right atrium from the superior and inferior vena cavae and than passes to the right ventricle. From here it is pumped through the pulmonary circulation, to the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle and is pumped out through the aorta to the systemic circulation"where the oxygen is used and metabolized to carbon dioxide. Normally with each heartbeat, the right ventricle pumps the same amount of blood into the lungs as the left ventricle pumps out into the body. Veins transport blood to the heart, while arteries transport blood away from the heart, regardless of oxygenation-level, (e.g. the pulmonary arteries carry blood low in oxygen from the heart to the lungs). Veins generally have lower pressures than arteries.
The heart and circulatory system are required for life and cardiovascular diseases are major causes of death. The heart beats at a rate of 60 to 90 beats per minute (at rest). Exercise temporarily increases this rate, but lowers resting heart rate in the long term, and is good for heart health. Poor heart health increases the risk of CVD"preventable factors causing poor heart health are smoking, being overweight, not enough exercise, high cholesterol, and high blood pressure among others. Inherited factors such as some genetic disorders can also result in decreased heart function. The human heart and associated cardiovascular diseases are studied and primarily treated by cardiologists, although many specialties of medicine may be involved with their treatment. Diagnosis of CVD is often done by listening to the heart-sounds with a stethoscope, ECG or by ultrasound.
The heart is situated in the middle of the chest beneath the breastbone in the mediastinum, at the level of T5-T8. The largest part of the heart is usually slightly offset to the left (though occasionally it may be offset to the right). The heart is usually felt to be on the left side because the left heart is stronger, since it pumps to all body parts. The left lung in turn is smaller than the right lung because it has to accommodate the heart. The heart is supplied by the coronary circulation and is enclosed in the pericardial sac. The pericardium comprises two parts: the fibrous pericardium, made of dense fibrous connective tissue, and the serous pericardium. Between the outer parietal layer and the visceral serous layer is the pericardial cavity which contains the pericardial fluid which protects and lubricates the heart.
The pericardium separates the heart from the other mediastinal structures and also attaches to the mediastinal fascia, providing anchorage for the heart. The dorsal surface of the heart lies near to the vertebrae, and the anterior surface sits deep to the sternum and costal cartilages. The great veins, the superior and inferior venae cavae, and the great arteries, the aorta and pulmonary trunk, are attached to the superior surface of the heart, called the base, which is located at the level of the third costal cartilage. The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs near their articulation with the costal cartilages. The right side of the heart is deflected anteriorly, and the left side is deflected posteriorly.
The shape of the heart is similar to a pinecone, rather broad at the base and tapering to the apex. The apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. It is located posterior to the 5th intercostal space just medial of the left mid-clavicular line. An adult heart has a mass of 250"350 grams (9"12 oz). A typical heart is approximately the size of a fist: 12 cm (5 in) in length, 8 cm (3.5 in) wide, and 6 cm (2.5 in) in thickness. Given the general size difference between the sexes, the weight of a female heart is approximately 250"300 grams (9"11 ounces), and the weight of a male heart is approximately 300"350 grams (11"12 ounces). Well-trained athletes can have much larger hearts due to the effects of exercise on the heart muscle, similar to the response of skeletal muscle. Exercise results in the addition of protein myofilaments and this can result in hypertrophy where the size of individual cells are increased but not their number. The hearts of athletes can pump more efficiently at lower heart rates. However, enlarged hearts can have a pathological cause which can result in a heart of 1000 g (2 lb) in mass. Hypertrophic cardiomyopathy is one such cause. The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people.Source: Wikipedia