ANGIOLOGY 



Angiology is the description of the organs of circulation of the blood and lymph 

 — the heart and vessels. The heart is the central hollow muscular organ which 

 functions as a suction and force pump; the differences in pressure caused by its 

 contraction and relaxation determine the circulation of the blood and lymph, 

 It is situated in the middle mediastinal space of the thorax and is enclosed in a fibro- 

 serous sac — the pericardium. The vessels are tubular and run through almost all 

 parts of the body. They are designated according to their contents as blood- and 

 lymph-vessels. 



THE BLOOD- VASCULAR SYSTEM 



The blood-vascular system consists of: (1) The arteries, which convey blood 

 from the heart to the tissues; (2) the capillaries, microscopic tubes in the tissues, 

 which permit of the necessary interchange between the blood and the tissues; 

 (3) the veins, which convey the blood back to the heart. 



The blood-vessels are divided into the pulmonary and the systemic. The 

 pulmonary artery conveys the blood from the right ventricle of the heart to the 

 lungs, where it is arterialized, and is returned by the pulmonary veins to the left 

 atrium of the heart, and passes into the left ventricle. The systemic arteries 

 convey the blood from the left ventricle all over the body, whence it is returned by 

 the venae cav£e to the right atrium, and passes into the right ventricle.'- 



The term portal system is often applied to the portal vein and its tributaries 

 which come from the stomach, intestine, pancreas, and spleen. The vein enters 

 the liver, where it branches like an artery, so that the blood in this subsidiary 

 system passes through a second set of capillaries before being conveyed to the heart 

 by the hepatic veins and the posterior vena cava. 



The arteries (Arterife), as a rule, divide at an acute angle, giving off finer 

 and finer branches. In some cases branches come off at a right angle, and others 

 are recurrent, i. e., run in a direction opposite to that of the parent stem. The 

 intercommunication of branches of adjacent arteries is termed anastomosis. Most 

 commonly the connections are made by a iietwork of numerous fine branches which 

 constitute a vascular plexus (Plexus vasculosus). Relatively large communicating 

 branches (Rami communicantes) occur in certain places; they may be transverse 

 or in the form of arches. Wide-meshed networks of vessels are termed retia vas- 

 culosa. Terminal or end arteries are such as form isolated networks, i. e., do not 

 anastomose with adjacent arteries. A rete mirabile is a network intercalated in 

 the course of an artery. A collateral vessel (Vas coUaterale) is one which pursues 

 a course near and similar to that of a larger vessel. 



The veins (Venae) are in general arranged like the arteries, but are usually of 

 greater caliber. When a vein accompanies an artery, it is termed a vena comitans 

 or satellite vein and is usually homonymous ; in many places two veins accompany 

 a single artery. The primitive venous trunks do not run with the arteries, and most 

 of the superficial veins (Venae cutaneae) pursue independent courses. They anas- 

 tomose even more freely than the arteries, and large communicating branches 

 are very common. Venous plexuses (Plexus venosi) occur in many places. Some 

 veins which are enclosed bydense membranes and run usually in bony grooves are 



' It should be noted, however, that the lungs also receive arterial blood through the systemic 

 bronchial arteries. This blood is returned in part by the bronchial veins to the right atrium (ia- 

 directly), in part by the pulmonary veins to the left atrium. 



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