Final answer:
The narrowest type of vessel in the cardiovascular and lymphatic systems that facilitates fluid exchanges with surrounding tissues is known as a capillary. These are smallest blood vessels critical for the transfer of substances between blood and tissues, as well as for the movement of interstitial fluid into the lymphatic system.
Step-by-step explanation:
The narrowest type of vessel in the cardiovascular and lymphatic systems that engages in fluid exchanges with surrounding tissues is called a capillary.
Capillaries are the smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid. These vessels connect arterioles and venules, facilitating the transfer of substances between blood and tissues. Within the lymphatic system, similar structures known as lymphatic capillaries, or terminal lymphatics, allow for interstitial fluid to enter the lymphatic system and become lymph fluid.
Found in almost every tissue, lymphatic capillaries are absent in the central nervous system, bone marrow, bones, teeth, and the cornea of the eye. The capillary walls are thin, allowing single red blood cells to pass through in a process essential for the body's microcirculation and homeostasis.