Author
Home > Science > What is the Difference Between Vein and Venule?

Guilherme Mazui

•4 minutes to read

What is the Difference Between Vein and Venule?

🆚 Go to Comparative Table 🆚

Veins and venules are both part of the circulatory system, but they have distinct roles and structures. The main differences between veins and venules are:

  1. Size: Veins are larger blood vessels that carry blood towards the heart, while venules are the smallest veins that collect blood from capillaries.
  2. Diameter: The diameter of veins is measured in millimeters, whereas the diameter of venules is measured in micrometers.
  3. Structure: Veins have three layers: tunica adventitia, tunica media, and tunica intima. Venules have a similar structure, but their walls are thinner, consisting of endothelium, a thin middle layer with a few muscle cells and elastic fibers, and an outer layer of connective tissue fibers that constitute a very thin tunica externa.
  4. Function: Veins transport blood towards the heart, while venules drain blood from capillaries to the larger veins.
  5. Valves: Veins have one-way valves inside them that allow blood to flow in a forward direction towards the heart. These valves are especially important in the arms and legs to prevent backflow of blood in response to the pull of gravity. Venules do not have valves.
  6. Blood Pressure: Veins have lower blood pressure compared to arteries, and they are designed to hold a high percentage of the blood in circulation at relatively low pressures. This feature is termed high capacitance.

In summary, veins and venules are both involved in the circulation of blood, but they differ in size, structure, function, and blood pressure. Veins carry blood towards the heart, while venules collect blood from capillaries and transport it to the larger veins.

On this page
  • What is the Difference Between Vein and Venule?
  • Comparative Table: Vein vs Venule

    • Comparative Table: Vein vs Venule

    Veins and venules are both blood vessels that return blood from the capillaries back to the heart. However, there are some differences between them:

    Feature Veins Venules
    Definition Veins are blood vessels that carry blood toward the heart. Venules are extremely small veins, generally 8–100 micrometers in diameter.
    Diameter Veins have larger diameters than venules. Venules have much larger lumina and thinner walls than corresponding arterioles.
    Wall Composition Veins have walls that are thinner than arteries and contain the same three layers as arteries (tunica adventitia, tunica media, and tunica intima) but with less smooth muscle and connective tissue. Venules consist of endothelium, a thin middle layer with a few muscle cells and elastic fibers, and an outer layer of connective tissue fibers that constitute a very thin tunica externa.
    Valves Veins have venous valves, similar to the semilunar valves associated with the heart, that help keep the blood flowing toward the heart. Venules do not have valves.
    Blood Flow Veins carry blood from the body tissue to the right atrium of the heart (systemic) or from the lungs to the left atrium of the heart (pulmonary). Venules are the primary sites of emigration or diapedesis, in which white blood cells adhere to the endothelial lining of the vessels and then squeeze through the walls.

    In summary, veins are larger blood vessels that carry blood towards the heart, while venules are extremely small veins that play a crucial role in the exchange of blood cells and nutrients between arteries and veins.

    Read more:

    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.