What do veins look like?
Your veins make up an extensive network of blood vessels that wind their way through your entire body. Together, your veins and other blood vessels form a major part of your circulatory system. Your veins connect with venules and capillaries in many places. When mapped out in a drawing, your upper body circulatory system resembles the complex wires and circuits inside a computer. Your lower body circulatory system resembles an upside-down tree with two large branches (one on each leg) and many small twigs on each branch.
What color are veins?
Many people think veins are blue because they look blue through our skin. But that’s just a trick that our eyes play on us. Your veins are actually full of dark red blood — darker than the blood in your arteries, which is cherry red. The blood in your veins is darker because it lacks oxygen. Your veins look blue because of the way light rays get absorbed into your skin. Blood is always red both in your veins and arteries.
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What are veins made of?
Each vein is made of three layers of tissues and fibers:
- The tunica adventitia (outer layer) gives structure and shape to your vein.
- The tunica media (middle layer) contains smooth muscle cells that allow your vein to get wider or narrower as blood passes through.
- Thetunica intima (inner layer) has a lining of smooth endothelial cells, allowing blood to move easily through your vein.
Veins and arteries share this general structure. However, veins are different from arteries because they sometimes also contain one-way valves that keep blood flowing in the right direction. These valves are especially important in your legs, where they help blood move up toward your heart. If these valves get damaged, blood can leak backward and cause varicose veins or other problems.
Veins are also different than arteries when it comes to the thickness of their walls. Veins have thinner and less muscular walls. This is because veins have a lower level of pressure than arteries. So, their walls don’t need to be as thick to handle the pressure.
What are the different types of veins?
You have three types of veins that help your circulatory system function.
Deep veins
These veins can be found in your muscles and along your bones. Your deep veins do the important work of moving your oxygen-poor blood back to your heart. In your legs, your deep veins hold about 90% of the blood that travels back to your heart. Your deep veins contain one-way valves that keep your blood moving in the right direction.
Superficial veins
Your superficial veins are generally smaller than your deep veins. Like deep veins, they contain valves. Unlike deep veins, they’re not surrounded by muscle. Instead, your superficial veins can be found just underneath your skin. So, you can easily see them.
Your superficial veins carry blood from your outer tissues near the surface of your skin to your deep veins (via the perforating veins). But this blood moves more slowly since it’s not being directly squeezed into motion by surrounding muscles.
The largest vein in your body is a superficial vein called the great saphenous vein. It runs all the way from your ankle to your thigh in each leg.
Perforating veins
These veins are sometimes called connecting veins or perforator veins. They are short veins that carry blood from your superficial veins to your deep veins. Perforating veins contain valves that close when your calf muscles compress so that blood doesn’t flow backward from your deep veins to your superficial veins.
What makes blood flow in the veins?
Your veins need an external force to help push your blood in the right direction. One such force is your own breathing. As your lungs expand and your diaphragm moves, they create a suction force that helps your veins push oxygen-poor blood toward your heart. Another force is your body’s muscle movement, especially in your legs. In fact, your leg muscles play a vital role in helping your blood defy gravity and move upward from your feet and legs back to your heart. For this reason, the muscles in your calves are called your “second heart.”
The “second heart”
You might not realize that your lower leg muscles act as a powerful pump that squeezes the deep veins in your lower legs. This “second heart,” also called your peripheral heart, springs into action each time you take a step. When you place your foot onto the ground, your body weight squeezes the deep veins in the bottom of your foot. As a result, those veins push any blood that’s inside up toward your calf.
Then, when you lift your heel, your calf muscles squeeze the deep veins in your calf. Your blood keeps moving up toward your thighs and beyond. This incredible system allows the blood in your feet and lower legs to defy gravity and make its way back up to your heart.
Unlike your heart in your chest, your second heart only starts pumping when your legs move. And its pumping pace adjusts to however fast your legs are moving. So, if you’re running, your calf muscles will squeeze your veins more quickly than if you’re walking. No matter the pace, your second heart allows your blood to keep flowing and complete its circuits through your body. As a result, your organs and tissues continue to receive oxygen and nutrients to function at their best.
