Final answer:
The arteries represent the high-pressure part and veins the low-pressure part of the circulatory system, with arteries transporting blood away from the heart under higher pressure and veins bringing it back at a lower pressure.
Step-by-step explanation:
The high pressure and low pressure parts of the circulatory system are represented by the arteries and veins, respectively. Arteries, which transport blood away from the heart into progressively smaller vessels, maintain a higher pressure due to the heart pumping blood through them. Veins, on the other hand, return the blood to the heart and have lower pressure. The capillaries serve as the connection points where these two systems meet, presenting the sites for exchange of nutrients and waste products between blood and tissues.
Arterial walls are much thicker than those of veins due to the higher pressure of the blood flowing through them. This difference in thickness is visible when comparing micrographs of these vessels.
In conclusion, arteries characterize the high-pressure part of the circulatory system, while veins represent the low-pressure part, with capillaries serving as the crucial exchange points between them.