Last updated:10-15-2008
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The body's blood circulation consists of two separate circuits. The largest is called thesystemic circulation, And it supplies the entire body with iltmættet and nutrient-rich blood. The second is calledlung circuit, And it runs only blood to and from the lungs. The blood flowing to the lungs, the blood, as the body's other tissues has been drained of oxygen. The blood, flowing from the lungs, is here once again become saturated with oxygen, which is inhaled, and then exchanged with the blood in the outer sections of the lungs.

In between the two circuits sit-hearted. It is divided into two halves separated by a partition. The right half afiltede it pumps blood into the pulmonary circulation, and the left half heart pumps oxygenated blood to the systemic circulation (see cardiac structure).

When the heart pulling together, pumped blood into blood vessels with a certain pressure. Blood pressure is significantly higher in the systemic circulation than in the pulmonary circulation, as this blood must be spread further afield and to a greater resistance.

Pulse Årer (arteries)
The vessels, which leads blood away from the heart, called arteries or the arteries and the arteries, which carry blood transported back to the heart, known as veins or veins.

The body's largest artery is hovedpulsåren,aorta. It is about. 30 mm in diameter. Aortic receive blood from the heart, and from the departure of other major arteries to the head, neck, arms, legs and internal organs.
Arteries are built to have to continue with high blood pressure. They have a thick, strong muscular wall that allows blood to pass at high speed, without the pressure decreases much. It is, therefore, that a blood pressure measured at the upper arm or hand led for practical purposes, equals the pressure with which the blood leaving the heart.

Arteries prospering several times and ends inarterioles, The so-called resistance cut. They have in their wall of a spiral-shaped muscle that, when pulling together, making it possible to completely close the artery. This is the body able to control where the blood must run, and where it should not be run.

Capillarity (exchange cut)
Following the arterioles are the so-called capillary, the exchange cut clean, which is the smallest blood vessels. Their wall is only one cell wide, and contains gaps between cells. Through them exchanged oxygen and nutrients to the surrounding tissue.
(see similar blood vessels' Supporting structure).

Blood Årer, veins and venoler
From capillaries running the afiltede blood into venesystemet.
The pressure has now dropped so that only a few millimeters of mercury (mm Hg). Veins have thin walls relax, not built to withstand pressure. You can expand greatly, and the body uses venesystemet as storage of blood. About 80% of the body's blood in the veins.

The smallest veins statesvenolerne, Which collects in other veins. The major vein calledvena cavaAnd keep the body's blood to the right side of the heart from an upper and lower arm.

Nutrients receive vena cava from gastrointestinal agencies veins.

The lungs are a great arteriegren for each lung. It contains carbon-rich and afiltet blood. In lungekapillærerne exchanged these gases to the smallest parts of the lung tissue, alveoli, so the carbon dioxide can udåndes, and the indåndede oxygen can be brought into the body. Pulmonary veins leading the oxygenated blood to the heart.

The circuit has other functions than the transport of oxygen and nutrients. The blood contains a lot of other components, including white blood cells and platelets (see blood components).

Blood flows into the various organs and tissues is constantly evolving. It is, for example. appropriate with much blood to muscles and less blood to the gut when you grow hard physical work and vice versa after a meal. It may sometimes be appropriate to increase heart pumping ability, which increases blood pressure. These regulations governed mainly by hormonal systems, for example. by adrenaline.

The body also includes a lymfekredsløb that carries excess fluid, proteins and immune cells from the tissue and back to venesystemet. During the "cleaned" and "examined" by the lymphatic immune cells in the lymph nodes.





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