Final answer:
The simple squamous epithelial tissue called endothelium forms the inner linings of the tunica interna of blood vessels and is essential for various cardiovascular functions.
Step-by-step explanation:
The simple squamous epithelial tissue that forms the inner linings of the tunica interna of blood vessels is known as the endothelium. This specialized layer is continuous throughout the entire vascular system, playing a crucial role in cardiovascular health by facilitating capillary exchange, regulating blood flow, and potentially contributing to conditions like hypertension when endothelins are overproduced. The endothelium also lines the lymphatic system and is integral in processes such as filtration and diffusion across its surface, thanks to the thin, flat structure of its cells.