Disinguish between a venule and vein?

Venules and veins are both blood vessels that carry blood back to the heart, but there are some key differences between the two.

Venules

* Venules are small blood vessels that collect blood from capillaries and carry it to veins.

* Venules are typically less than 1 millimeter in diameter.

* Venules have thin walls that are made up of a single layer of endothelial cells.

* Venules do not have valves.

Veins

* Veins are larger blood vessels that carry blood from venules to the heart.

* Veins are typically more than 1 millimeter in diameter.

* Veins have thicker walls that are made up of three layers of tissue: the tunica intima, the tunica media, and the tunica adventitia.

* Veins have valves that help to prevent blood from flowing backward.

In general, venules are smaller than veins, have thinner walls, and do not have valves. Veins are larger than venules, have thicker walls, and have valves.