Morphological and Functional Characteristics of Blood and Lymphatic Vessels

Abstract

Blood vessels constitute the blood-containing circulation, representing a closed system of arteries and veins, which are connected by the capillaries. The blood vascular system provides all tissues with oxygen, nutrients, and immune cells and undertakes the evacuation of metabolites. Arteries deliver oxygenated blood from the lung to the arterioles and further to the capillaries in the periphery of the body where a bidirectional exchange between blood and tissue occurs. The task of veins is to collect deoxygenated blood and to transport it back to the heart. The lymphatic system works auxiliary to the venous vasculature by collecting excess interstitial fluid, proteins, particles, and cells that have leaked into tissues, returning these into the blood. It takes over approximately 10% of the capillary filtrate residuum. Importantly, lymphatic vessels directly absorb dietary lipids from the gut and deliver them to the blood circulation. Before returning lymph fluid into the blood, it is passed through lymph nodes for presentation of foreign components to immune cells. Concomitantly, lymphatic vessels guide immune cells to the lymphoid organs.