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Veins have a much higher compliance than arteries (largely due to their thinner walls.) Veins which are abnormally compliant can be associated with edema. Pressure stockings are sometimes used to externally reduce compliance, and thus keep blood from pooling in the legs.
However, transmural pressure across the wall of the blood vessels increases down this zone due to gravity. Consequently the vessels wall are more stretched so the caliber of the vessels increases causing an increase in flow due to lower resistance. Zone 4 can be seen at the lung bases at low lung volumes or in pulmonary edema.
Transmural pressure is the difference in pressure between two sides of a wall or equivalent separator. According to myogenic theory smooth muscle contract in response to increased transmural pressure and relax to decreased transmural pressure For body vasculature or other hollow organs, see Smooth muscle#External substances
A list of veins in the human body: Veins of the heart. Coronary sinus. Great cardiac vein; Oblique vein of left atrium; Middle cardiac vein; Small cardiac vein; Pulmonary veins; Superior vena cava. Brachiocephalic vein. Inferior thyroid vein; Inferior laryngeal vein; Pericardial veins; Pericardiophrenic veins; Bronchial veins; Vertebral vein ...
The jugular venous pressure (JVP, sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system via visualization of the internal jugular vein. It can be useful in the differentiation of different forms of heart and lung disease .
The venous valves serve to prevent regurgitation (backflow) due to the low pressure of veins, and the pull of gravity. [1] They also serve to prevent the over-widening of the vein. [20] [21] A venous valve is bicuspid (having two leaflets) and is formed by an infolding of part of the tunica intima on either side of the lumen of the veins.
In a standing position, the main outflow from the head is through the vertebral venous system because the internal jugular veins, located primarily between the carotid artery and the sternocleidomastoid muscle are partially or completely occluded due to the pressure from these structures, and in a supine position, the main outflow is through ...
Intrapleural pressure depends on the ventilation phase, atmospheric pressure, and the volume of the intrapleural cavity. [2] At rest, there is a negative intrapleural pressure. This provides a transpulmonary pressure, causing the lungs to expand. If humans didn't maintain a slightly negative pressure even when exhaling, their lungs would ...