If you’re curious about how blood flows through our body, you’ve probably heard about valves. But which vessels have valves? In this ultimate guide, we’re going to talk about the different types of blood vessels and where valves are found.
The three types of blood vessels
Before we talk about valves, let’s review the three types of blood vessels: arteries, veins, and capillaries.
Arteries are muscular and elastic blood vessels that carry oxygen-rich blood away from the heart to other parts of the body. Because they receive blood directly from the heart, arteries are under high pressure.
Arteries do not have valves since the pressure from the heart’s pumping action is enough to propel the blood through the vessel.
Veins are blood vessels that carry oxygen-depleted blood from the tissues back to the heart. Unlike arteries, veins have thinner walls and are less muscular.
Most veins in the body have valves. This is because the flow of blood in veins is not propelled directly by the heart but relies on other mechanisms like muscles contractions in the limbs.
Capillaries are the smallest blood vessels in the body. Their walls are incredibly thin, and they connect arterioles to venules.
Capillaries do not have valves since their walls are so thin and fragile, and they mainly rely on diffusion to transport molecules between the blood and the body’s tissues.
Where do valves appear in the venous system?
As mentioned, most veins in the body have valves. But where do we find them?
Some of the most common areas where valves are found are in the veins of the lower extremities, namely the legs and feet. Valves in this area help the blood move back up towards the heart against the force of gravity.
When these valves are not functioning correctly, blood can pool in the veins, leading to varicose veins or even deep vein thrombosis.
Veins in the hands, arms, and shoulders also have valves. However, these valves are not as prominent as those in the legs.
Valves are also found in the veins in the pelvis area. These veins, also called gonadal veins, drain blood from the reproductive organs.
Head and neck
Veins in the neck, called jugular veins, also have valves. The jugular veins are responsible for draining blood from the head and neck regions back to the heart.
The function of valves in the venous system
Now that we know which veins have valves, let’s talk about their function in the venous system.
Prevent backflow of blood
The primary function of valves is to prevent the backflow of blood. They ensure that the blood flows in one direction towards the heart.
For example, in the lower extremities, valves create compartments that prevent the pooling of blood in the veins. When we walk or contract our leg muscles, the valves open and allow blood to flow upward towards the heart. Then, they close to prevent blood from flowing backward.
Assist in blood transport
Valves also assist in the transport of blood back to the heart. As mentioned, veins do not receive direct blood flow from the heart-like arteries, so they need other mechanisms to move blood. The valves work to aid in that transport by dividing the veins into compartments that help push blood toward the heart instead of allowing it to pool within one section of the vein.
Medical conditions that affect valves in veins
Now that we know how valves function, let’s discuss some medical conditions that can affect them.
When the valves in the veins, especially the lower extremities, become damaged, blood can pool in the vein and form a bulging, twisted, and sometimes painful vein. This condition is called varicose veins. Varicose veins are more common in women than men, and they can lead to complications like blood clots.
Deep vein thrombosis (DVT)
DVT occurs when a blood clot forms in a vein, usually in the legs, and obstructs blood flow. DVT can be challenging because it is often asymptomatic. However, it’s important to catch this condition early on as it can lead to a pulmonary embolism.
Chronic venous insufficiency (CVI)
CVI is a condition caused by damaged valves in the lower extremity veins. It causes blood to pool in the veins, leading to leg swelling, skin changes, and leg ulcers. CVI can be a progressive condition, and it’s important to manage it early on to prevent complications.
Valves are present mainly in the veins and not in the arteries. They work to ensure blood flows in one direction towards the heart and to assist in the blood’s transport without the force of the heart’s pumping. Dysfunction in these valves can lead to various medical issues, such as varicose veins, DVT, and CVI.
- Q: Which blood vessels have valves?
- A: Valves are mainly present in veins.
- Q: What is the function of valves in the venous system?
- A: Valves prevent backflow of blood and assist in the transport of blood back to the heart.
- Q: What are some medical conditions that can affect valves in veins?
- A: Some medical conditions that can affect valves in veins include varicose veins, deep vein thrombosis (DVT), and chronic venous insufficiency (CVI).