20.1a Comparison of the different vessel types

What are companion vessels?

Arteries and veins that lie next to each other and serve the same body region.

Why are arteries and veins considered companion vessels?

They supply and drain the same tissues in a region.

How does the tunica media of arteries compare to veins?

Arteries have a thicker tunica media than veins.

How does the lumen of arteries compare to veins?

Arteries have a narrower lumen than veins.

Why do arteries have a thicker tunica media?

To handle higher pressure and control blood flow.

What fibers are abundant in arteries?

Elastic and collagen fibers.

What is the function of elastic fibers in arteries?

They allow the vessel to stretch and recoil.

Why are arteries more resilient than veins?

They have more elastic and collagen fibers.

Arteries are resistant to changes in what?

Blood pressure.

How does the tunica externa of veins compare to arteries?

Veins have a thicker tunica externa than arteries.

How does the lumen of veins compare to arteries?

Veins have a larger lumen than arteries.

Why do veins have less elastic and collagen fibers?

They operate under lower pressure.

What happens to a vein if there is no blood inside?

The wall collapses.

Why can veins collapse easily?

They have less structural support and lower pressure.

What layer do capillaries contain?

Only the tunica intima.

What structures make up capillaries?

Endothelium and a basement membrane.

Do capillaries have a subendothelial layer?

No, they do not.

Why are capillary walls thin?

To allow rapid exchange of gases and nutrients.

Which vessel type is specialized for exchange?

Capillaries.

Which vessel type is most resistant to pressure changes?

Arteries.

Which vessel type can collapse when empty?

Veins.