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The externa, alternatively known as the tunica adventitia, is composed of collagen fibers and elastic tissue—with the largest arteries containing vasa vasorum, small blood vessels that supply the walls of large blood vessels. [3] Most of the layers have a clear boundary between them, however the tunica externa has a boundary that is ill-defined.
Galen believed the arterial blood was created by venous blood passing from the left ventricle to the right through 'pores' between the ventricles. [92] Air from the lungs passed from the lungs via the pulmonary artery to the left side of the heart and created arterial blood. [95] These ideas went unchallenged for almost a thousand years. [92] [95]
The tunica intima (Neo-Latin "inner coat"), or intima for short, is the innermost tunica (layer) of an artery or vein. It is made up of one layer of endothelial cells (and macrophages in areas of disturbed blood flow), [1][2] and is supported by an internal elastic lamina. The endothelial cells are in direct contact with the blood flow.
The vascular wall is subdivided into three layers known as the tunica externa, tunica media, and tunica intima. The aorta is covered by an extensive network of tiny blood vessels called vasa vasorum, which feed the tunica externa and tunica media, the outer layers of the aorta. [13]
The heart is a muscular organ situated in the mediastinum.It consists of four chambers, four valves, two main arteries (the coronary arteries), and the conduction system. The left and right sides of the heart have different functions: the right side receives de-oxygenated blood through the superior and inferior venae cavae and pumps blood to the lungs through the pulmonary artery, and the left ...
Capillaries join the arteries and veins. The circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. [1][2] It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek kardia ...
As a part of the aorta, the entire body, with exception of the respiratory zone of the lung and the heart. The aortic arch, arch of the aorta, or transverse aortic arch (English: / eɪˈɔːrtɪk / [1][2]) is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of ...
Pericardium. Walls of the heart, showing pericardium at right. The pericardium (pl.: pericardia), also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. [1] It has two layers, an outer layer made of strong inelastic connective tissue (fibrous pericardium), and an inner layer made of serous ...