. Cunningham's Text-book of anatomy. Anatomy. 868 THE VASCULAE SYSTEM. in different tissues. The small arteries which end in them are known as capillary arterioles, and the venous radicles which commence from them are appropriately termed capillary veins. Structure of Arteries and Veins.—The delicate elastic endothelial membrane which forms the wall of the simplest capillaries extends also, as a continuous lining, throughout the whole of the blood-vascular system. In the arteries the con- stituent cells are fusiform, narrow, and pointed, whilst in the veins they are some- what shorter and broa
. Cunningham's Text-book of anatomy. Anatomy. 868 THE VASCULAE SYSTEM. in different tissues. The small arteries which end in them are known as capillary arterioles, and the venous radicles which commence from them are appropriately termed capillary veins. Structure of Arteries and Veins.—The delicate elastic endothelial membrane which forms the wall of the simplest capillaries extends also, as a continuous lining, throughout the whole of the blood-vascular system. In the arteries the con- stituent cells are fusiform, narrow, and pointed, whilst in the veins they are some- what shorter and broader. The most essential structural difference between capillaries on the one hand and the arteries and veins which they unite together on the other, is the presence, in both of the latter, of involuntary muscular fibres which are interposed between the endothelial lining and the outer connective tissue sheath. In small vessels, capillary arte- rioles, the muscle cells are few in number and more or less scattered. In larger vessels the walls become stronger and thicker, muscular fibres - T. media Fig. C B A2 Ai -Structure of Blood-vessels (diagrammatic). A1, Capillary—with simple endothelial walls. A2, Larger capillary —with connective tissue sheath, "adventitia ; B, Capillary arteriole—showing muscle cells of middle coat, few and scattered. C, Artery—muscular elements of the tunica increase and form a COntinUOUS layer, media forming a continuous layer. , ., , ,, , , -t- . whilst yellow elastic and ordinary white connective tissue are added in varying proportions. The walls of the vessels thus become more complex, and numerous strata may be distinguished ; which, for convenience, are regarded as forming three layers, known as the tunica intima and the middle and outer tunics. Superadded to the tunics is the investing fibrous sheath or vagina basis. Structure of Arteries.—The walls of arteries are stronger and thicker than those of vein
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
