Veins and arteries are very important parts of our blood system, but they look and work differently. Here are some key differences between them:

1. Wall Structure:

   • Arteries have thick walls that can be about 1 mm. This helps them carry blood that flows under high pressure. For example, the pressure in arteries is usually around 120 mmHg.
   • On the other hand, veins have thinner walls that are about 0.5 mm. They have less muscle and not as many stretchy fibers because they deal with lower pressure. The pressure in veins is usually between 5-10 mmHg.

2. Lumen Size:

   • The inside of arteries, called the lumen, is narrower. This helps keep the blood pressure high.
   • Veins have a wider lumen that can be up to 2 cm. This makes it easier for them to bring a larger amount of blood back to the heart.

3. Valves:

   • Veins have special one-way valves. These valves stop blood from flowing backward. In fact, about 70% of all the blood in our bodies is in the veins at any time.
   • Arteries do not have valves because they carry blood straight from the heart.

These differences in structure help veins and arteries do their jobs well in moving blood around our bodies.