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They run between the pulmonary segments from which they drain the blood. [1] At the root of the lung, the right superior pulmonary vein lies in front of and a little below the pulmonary artery; the inferior is situated at the lowest part of the lung hilum. Behind the pulmonary artery is the bronchus. [2]
Arteries are further divided into very fine capillaries which are extremely thin-walled. [4] The pulmonary veins return oxygenated blood to the left atrium of the heart. [3] The pulmonary arteries have both an internal and external elastic membrane, whereas pulmonary veins have a single (outer) elastic layer. [5]
The pulmonary artery pressure (PA pressure) is a measure of the blood pressure found in the main pulmonary artery. This is measured by inserting a catheter into the main pulmonary artery. [ 13 ] : 190–191 The mean pressure is typically 9–18 mmHg, [ 14 ] and the wedge pressure measured in the left atrium may be 6–12 mmHg.
In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95–100%) with oxygen. In all veins, apart from the pulmonary vein, the saturation of hemoglobin is about 75%. [15] [16] (The values are reversed in the pulmonary circulation.)
The root of the right lung lies behind the superior vena cava and part of the right atrium, and below the azygos vein.That of the left lung passes beneath the aortic arch and in front of the descending aorta; the phrenic nerve, pericardiacophrenic artery and vein, and the anterior pulmonary plexus, lie in front of each, and the vagus nerve and posterior pulmonary plexus lie behind.
The anatomy of arteries can be separated into gross anatomy, at the macroscopic level, and microanatomy, which must be studied with a microscope.The arterial system of the human body is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs.
This concept is generally attributed to an article by West et al. in 1964, [1] but was actually proposed two years earlier by Permutt et al. [2] In this article, Permutt suggests "The pressure in the pulmonary arteries and veins is less at the top than at the bottom of the lung. It is quite likely that there is a portion of the lung toward the ...
Though veins might make it appear as such, human blood is never naturally blue. [3] The blue appearance of surface veins is caused mostly by the scattering of blue light away from the outside of venous tissue if the vein is at 0.5 mm deep or more. Veins and arteries appear similar when skin is removed and are seen directly. [4] [5]