History Of Blood-vessel: Artificial blood vessels underwent a period of explosive evolution in the late 1950s. Very little was added after that time. Early in the history of blood-vessel surgery, about 1956, the only source for replacement of arteries was aortas removed from young persons dying of brain injury or accident. There was a great scarcity and doctors had to make agonizing decisions regarding which patient could receive an available graft. When Dacron artery grafts became available, it was found that these worked better than the human transplants. Following the development of Dacron grafts, one pioneer in vascular surgery said, "Once this was established, everyone stopped worrying about the shortage of human artery grafts."
An important factor in the response of the pituitary is its blood supply. Pituitary blood flow was receiving considerable attention with encouraging results. Because the blood of one portal vessel seems to enter a restricted zone of the anterior lobe of the pituitary, this suggests the possibility that particular hormones | are specifically controlled by restricted axes -parts of the hypothalamus, parts of the portal vessels, and parts of the anterior lobe. A method was developed that prevents contamination of the blood collected from the portal vessels in the rat, and with this technique it was expected to be possible to determine the rate of secretion of a given hypothalamic factor.
From the capillaries the blood, on the way back to the heart, empties into small vessels (venules) and then into larger and larger veins and finally reaches the great veins (venae cavae) which return the blood to the right atrium of the heart. . From this thin-walled chamber the blood empties into the more muscular right ventricle, which ejects it forcefully into the main pulmonary artery. This large vessel divides into right and left branches which supply each lung. By a se: of branches, similar to that described for aorta, these arteries divide in the lung into sma and smaller branches, finally becoming a i network of pulmonary capillaries.
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