and observed under the scanning electron microscope. The carotid body received the proper carotid body artery from the common carotid body artery, which arose from the external carotid or occipital artery and gave off subsidiary branches to the tissues near the carotid body. The proper carotid body artery divided in the carotid body, ultimately breaking up into thick (main) or thin (subsidiary) arterial terminals to form the vascular plexus of the carotid body. This plexus contained both thick and thin capillaries. The thick capillaries arose from the thick and thin arterial terminals and formed the basic capillary network of the carotid body. The thin capillaries were only subsidiary, intercalated among the thick capillaries. A few accessory twigs of the proper carotid body artery passed through the carotid body and supplied the adipose and other tissues around the carotid body. Many venules arose from the thick capillaries of the carotid body and were collected into rostral and caudal efferent veins. These efferent veins received the veins from the tissues adjacent to the carotid body, and drained into the internal jugular vein. No arterio-venous anasto-mosis was found in, on or around the carotid body. The common carotid body artery and its subsidiary branches showed, at their origins, marked constrictions indicative of the arterial cushions, though the proper carotid body artery and its accessory twigs were not provided with such clear constrictions. These findings suggest that the inflow of blood into the common carotid body artery may be regulated by its constriction especially of its arterial cushion, and that the subsidiary branches of the common carotid body artery and the accessory twigs of the proper carotid body artery may act as bypass-routes to eliminate the excessive inflow of blood into the carotid body. It is considered that the thin arterial terminals and thin capillaries may act as buffer channels to homogenize the blood flow within the carotid body. The blood vascular bed of the rat carotid body was reproduced with methacrylate.
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