Final answer:
Arterioles are the primary contributors to resistance in the systemic arterial system due to their small lumen size and capacity for vasodilation and vasoconstriction, despite capillaries being smaller.
Step-by-step explanation:
The greatest resistance to blood flow in the arteries of systemic circulation is contributed by arterioles. Arterioles are termed resistance vessels due to their small lumen, which significantly slows the flow of blood from arteries, creating the greatest resistance in the vascular network. Although capillaries are smaller in size, there are many more capillaries which collectively have a larger total cross-sectional area, so the resistance across them is less than that across arterioles. Vasodilation and vasoconstriction of arterioles are critical mechanisms regulating systemic blood pressure by altering resistance.
It is also important to note that conditions like arteriosclerosis can further increase resistance within the arteries. When compliance of arterial walls is reduced, pressure and resistance increase, making it harder for the heart to pump blood and leading to higher blood pressure and complications such as heart disease.