Final answer:
The systemic veins are responsible for returning deoxygenated blood from the body's tissues back to the heart, specifically to the right atrium. They are part of the systemic circulation, distinct from the pulmonary circulation where the oxygenation of blood occurs. Option number a is correct.
Step-by-step explanation:
Function of Systemic Veins
The systemic veins function by returning deoxygenated blood back to the heart. After the body's organs and tissues have extracted oxygen from the blood for metabolic processes, the now oxygen-poor blood is collected by systemic veins. These veins transport the blood through a network that increases in size from capillaries to venules and eventually to larger veins, such as the inferior vena cava and the superior vena cava. The collected blood is then delivered to the right atrium of the heart. This is a crucial step in systemic circulation, contrasting with pulmonary circulation, where blood is oxygenated in the lungs and returned to the left atrium of the heart via the pulmonary veins.
The process of systemic and pulmonary circulation is vital for the ongoing oxygenation and removal of carbon dioxide from the bloodstream. Remember that systemic veins do not deliver blood to the capillaries but rather gather the deoxygenated blood from them. Additionally, the pulmonary veins are the ones tasked with carrying oxygen-rich blood, a unique characteristic as they are the only veins that do so.