ARTERIES
The highways of our circulatory system are muscular tubes responsible for delivering oxygen-rich blood throughout the body. They branch out extensively, starting with the aorta, the largest artery leaving the heart, and progressively narrow into smaller vessels. This elaborate network ensures efficient transport of vital oxygen, nutrients, and hormones to nourish our cells and tissues. The thick, elastic walls of arteries are specially adapted to withstand the strong, pulsating force of blood ejected from the heart. However, unhealthy lifestyle choices like smoking can damage these walls, leading to a buildup of plaque and potentially life-threatening conditions like atherosclerosis.

THE SPLEEN
Acts as a filter and storage unit within the circulatory system. Located in the upper left abdomen, this fist-sized, spongy organ filters blood, removing old or damaged red blood cells and cellular debris. It also serves as a reservoir, storing platelets needed for clotting and white blood cells that fight infection. In cases of blood loss, the spleen can contract and release additional blood cells back into circulation. However, due to its location, the spleen is susceptible to injury and may require removal in certain situations.
VEINS
They are responsible for carrying deoxygenated blood back to the heart. Unlike arteries, which have thick, muscular walls to handle the pumping pressure, veins have thinner, more flexible walls. One-way valves lining the veins prevent blood from flowing backward and ensure efficient delivery of oxygen-depleted blood towards the heart. The largest vein, the vena cava, delivers blood from the entire body to the right atrium of the heart, completing the circulatory loop. Maintaining healthy veins is crucial for proper blood circulation and overall well-being. This includes preventing conditions like varicose veins, which can develop due to weakened valves or increased pressure in the veins.

VENA CAVA
A singular but paired vascular structure reigns supreme as the largest vein in the human body. This duo, the superior and inferior vena cava, acts as a highway system, responsible for delivering deoxygenated blood back to the heart. The superior vena cava collects blood from the upper body, head, and arms, while the inferior vena cava gathers blood from the lower body, legs, and organs. Both vena cavae culminate in the right atrium of the heart, completing the circulation loop and ensuring a constant flow of blood for oxygen replenishment. Maintaining a healthy vena cava is vital for proper blood return and overall cardiovascular function. Conditions like thrombosis, blood clot formation within the vena cava, can impede blood flow and require medical attention.

References:
American Heart Association. (2020, February 27). Understanding adult cardiovascular diseases. Centers for Disease Control and Prevention.
Cleveland Clinic – Spleen: Function, Location & Size, Possible Problems
Kenhub – Spleen: Anatomy, location and functions
Marieb, E. N., & Hoehn, K. N. (2010). Human anatomy & physiology (8th ed.). Pearson Education
Mayo Clinic – Splenectomy
Moore, D. R., & Robson, K. D. (2012). Arteries. In D. R. Moore (Ed.), Clinically oriented anatomy (7th ed.) (pp. 172-173). Lippincott Williams & Wilkins. [ScienceDirect Source]
National Institutes of Health. (2021, April 12). How Does the Circulatory System Work? National Institutes of Health.
Science Direct – The spleen: structure and function
Tortora, G. J., & Derrickson, B. (2016). Principles of anatomy and physiology (15th ed.). John Wiley & Sons