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 isenclosed 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 amet ange 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 vene cave 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 hepatie veins and the posterior vena cava. 
The arteries (Arteriw), 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, 7. 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 network 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, 7. e., do not 
anastomose with adjacent arteries. A rete mirabile is a network intercalated in 
the course of an artery. <A collateral vessel (Vas collaterale) is one which pursues 
a course near and similar to that of a larger vessel. 
The veins (Ven) are in general arranged like the arteries, but are usually of 
greater caliber. When a vein accompanies an artery, it is ter med a vena comitans 
or satellite vein and is usually homonymous; in many places two veins accompany 
asingle artery. The primitive venous trunks do not run with the arteries, and most 
of the superficial veins (Ven cutanex) 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 by dense membranes and run usually in bony grooves are 
Tt should be noted, however, that the lungs also receive arterial blood through the sy stemic 
bronchial arteries. This blood is returned in part by the bronchial veins to the right atrium (in- | 
directly), in part by the pulmonary veins to the left atrium. 
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