The heart
Acts as a pump for blood in the body. The heart is a wall divided into two separate pumping systems, right and left. Right half pumps blood to the lungs, and left half pumps blood to the rest of the body. Each of these halves are subdivided into a pre-chamber, an atrium, and a heart, ventriklen.  When blood comes to the heart received it from the body's two major veins, superior vena cava (upper), and inferior vena cava (the lower). These two veins have received afiltet blood from the rest of venesystemet (see bloodstream). The blood runs into the right pre. From here, run it, partly passive and partly by contraction of the pre-chamber, into the right heart through a cardiac valve (tricuspidalklappen) (see heart valves. When the right arteries subsequently pulling together, prevents this noon After the blood has been oxygenated in the lungs turning it back to the heart, left pre which at the same principle as before, headed to the left arteries (over mitralklappen). From there the oxygenated blood pumped out through aortaklappen, and out of hovedpulsåren, aorta. The two forkamre, and the two ventricles pulling together synchronously, so the heart is emerging as one pump. Heart wall is almost overwhelmingly made up of the heart muscle (myocardial), and left heart half is much thicker than the right, then it must make a significantly higher blood pressure. On the inside is the heart lined with flat cells, called endothel, which represents endokardiet and which continues in the endothel located on the inside of blood vessels' Supporting (see below).
Extremely at heart, it is surrounded by a double layer pericardial sac. The innermost layer of the heart bag holding the heart, and the outer layer is attached to the surrounding organs, including diaphragm and lungs. In between the two layers, there is a thin liquid film, which makes the heart can beat almost smooth. Pulse Årer, arteries
Arteries (arteries pulse) is the blood vessels leading from the blood to the heart tissue. (See bloodstream). They are made of three layers, which makes them unable to resist, and continue the high pressure generated in the heart when it strikes. Extremely there is a thin bindevævslag, including anchoring the artery to the surroundings. The middle layer is by far the largest, and consists of muscle cells and elastic fibers, which makes the tank strong, and able to pursue a high pressure in the blood.
Internally, there is a endothellag surrounded by a little connective tissue. Endothelet is an extension of the heart endokardium, and it gives the tank a smooth inside, so the blood flowing smoothly, and without creating turbulence. If endothelet damaged, can cause blood clot formation and arteriosclerosis.Resistance Skarsholm, arterioles
The smaller arteries are, the less their muskellag. The smallest arteries called arterioles, and the smallest arterioles has only a single muskelcellelag around him. In English, called the opposition cut because the muscle layers can pull together so much that the artery will close. This increases the resistance. Artery muskellag can also pull together, and reduce karrets diameter. The increased resistance increases blood pressure. The blood from the artery will run for the exchange cut clean.Exchange Skarsholm, capillarity
The very smallest blood vessels consist only of single endothel layer, and there are "gaps" between endothelial cells. This allows oxygen, nutrients, and individual cells are exchanged for a tissue. The higher pressure in capillary driver substances out, pressure falls gradually, and wastes from the tissues "sucked" into the last end of kapillærnettet. The entries also exchanged because of differences in concentration.Blood Årer, veins and venoler
The smallest veins called venoler, and they receive it by-oxygenated blood from capillaries. Venolerne timber in the larger veins, veins, which in turn timber in even larger veins. Blood pressure in the veins is very low, so their walls are nowhere near as thick as arterial.
They also consists of three layers, but the middle muskellag is very thin. Therefore, the veins expand greatly, and approx. 80, the body's blood found in the rest of the veins.
Since there is a high pressure to bring veneblodet back to the heart, veins are equipped with veneklapper, only allowing the blood to run against her heart. Ben and armes large veins is close to the muscles, and when the muscles are used, squeezes the veins empty of blood. Because the flaps kept blood from the heart. |
