Rabu, 30 Desember 2015


Our body also needs a transportation system to deliver nutrients, oxygen, and carbon dioxide. The transportation system in our body is the circulatory system, which consists of the heart, blood vessels, and blood.
A.        Blood Vessels
In the cardiovascular system, there are three types of blood vessels:
1.       Artery
(Picture. Human blood  circulation system)
Artery is a blood vessel transporting blood from heart throughout the body. They are hidden inside our body. The biggest artery is the one closest to the heart called aorta. Aorta branches into artery. Artery still brances into smaller artery called arteriole. At the tip of arteriole, it is formed many soft branches and it becomes capillary beds called artery capillaries.
2.       Vein
Vein is blood vessel transporting blood from the body back to heart. They are located near our skin surface and look bluish. The walls of veins are thin and not elastic. You cannot feel their pulse. Veins have valves along their length. Their function is to keep the blood flowing in one direction. Besides that, they also maintain blood flows since there is no pump in these veins.
The differences of artery and vein
Stream direction
Away from the heart
Toward the heart
Vessel’s wall
Thick and elastic
Thin and not elastic
Can be felt
Cannot be felt
Far from skin surface
Near skin surface
One near the heart
Along the vessels
Blood characteristic
Clean, except pulmonary artery ( carry blood to the lungs)
Dirty, except pulmonary vein ( carry blood from lungs back to the heart)
3.       Capillaries
The blood vessels branch into smaller vessels called capillaries.

At the tip of the capillaries, arteries and veins join. Therefore, our blood vessel is a closed blood vessel. Our blood always flows or remains in blood vessels.
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A.        Heart
Heart is necessary to pump the blood throughout the body and located slightly on left side in chest cavity. The heart size is almost the same as our fists. Heart muscle is similar with skeletal muscle, but it has branch structure (anastomose). Human heart is devided into four chambers:
a)      left atrium, have function to pumping blood into  the left ventricle
b)      right atrium, have function to pumping blood into  the right ventricle
c)       left ventricle, have function to pumping throughout the body through aorta              

d) right ventricle, have function to pumping blood into lungs through pulmonary artery.        
      The ventricle will has a thicker muscle wall than the atrium. It is because ventricles have to work harder, namely to pump blood to all parts of body. There are valves between the atrium and ventricle. The valves function as to prevent blood from flowing back to the atrium. Heart wall is composed of three layers, pericardium ( the outermost layer), myocardium ( central layers), and endocardium ( the innermost layer of heart chamber).
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