The parts of your circulatory system are your: Heart, a muscular organ that pumps blood throughout your body. Blood vessels, which include your arteries, veins and capillaries. Blood, made up of red and white blood cells, plasma and platelets.

Arteries are thin, muscular tubes that carry oxygenated blood away from the heart and to every part of your body. 

Vena Cava. It consists of collagen and elastic connective tissue. It is this outmost layer that is primarily responsible for the superior vena cava’s flexibility.

Venule. A venule is a small blood vessel in the microcirculation that allows deoxygenated blood to return from capillary beds to larger blood vessels called veins.

References:
Circulatory System. (2021 September 9). Cleveland Clinic. Retrieved from https://my.clevelandclinic.org/health/body/21775-circulatory-system

White, H. J., & Soos, M. P. (2021 July 26). Anatomy, Thorax, Superior Vena Cava. National Center for Biotechnology Information. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK545255/

Venules. (2020 August 14). Libre Texts. Retrieved from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/18%3A_Cardiovascular_System%3A_Blood_Vessels/18.3%3A_The_Venous_System/18.3A%3A_Venules