Anatomy Chapter 9 - vascular system

List the layers of blood vessel walls and their characteristics in order from outermost to innermost. Which layer forms capillaries?

1. Tunica externa aka adventitia - connective tissue layer

2. Tunica media - smooth muscle, elastic fibers, or mix of both

3. Tunica intima - endothelium

Capillaries are made of only tunica intima/endothelium

Name the three different types of arteries and their characteristics.

1. Elastic (conducting) arteries - primarily elastic fibers; just the aorta

2. Muscular (distributing) arteries - 50/50 smooth muscle and elastic fibers; capable of vasoconstriction/vasodilation

3. Arterioles - very small & all smooth muscle, also capable of vasoconstriction and vasodilation

Name the three different types of veins and their characteristics.

1. Large veins - inferior & superior vena cava

2. Small veins - way less tunica media than distributing arteries; have valves to prevent backflow

3. Venules - many small unnamed veins

What is the vasa vasorum?

Vessels supplying other blood vessels with blood.

What causes varicose veins?

caused by pooling of blood in broken/leaking valves

What blood vessels are smaller than venules and arterioles?

Capillaries

Describe the three mechanisms of venous return.

Vasoconstriction - tunica media (muscle and elastic fibers) creates small decrease in lumen diameter & squeezes blood along vein

Skeletal muscle pump - skeletal muscles surrounding veins squeeze blood upward

Respiratory pump - less thoracic pressure and more abdominal pressure during inhalation moves blood into thoracic veins and right atrium

What is fainting called and why does it happen?

Called syncope; caused by cerebral ischemia (not enough blood flow to brain)