B9.3 Blood vessels

What are blood vessels?

An extensive, interconnected network of hollow tube-like structures through which blood flows through

Describe the structure of arteries

• Carry blood away from the heart

• Thick outer wall to withstand high blood pressure being pumped out the ventricles

• They contain elastic muscle tissue that can stretch and relax with blood pressure changes

Describe the structure of the capillaries

• Smallest type of blood vessel

• They have thin walls (only a single cell thick) to:

  • Easily exchange substances (like nutrients + oxygen) with cells

  • Take away waste products (like CO2)

• Capillaries have low blood pressure, so it flows more slowly

Function of capillaries

• Provides oxygen and nutrients to the body’s cells

• Release waste and carbon dioxide from the body’s cells

Describe the structure of veins

• Carries blood to the heart

• Relatively thin walls, largest lumen

  • Blood enters the veins after capillaries with lower pressure, so the walls don’t need to be very strong

• They have valves to prevent backflow and keep blood moving towards the heart

• Skeletal muscle contractions help push blood through veins toward the heart

What are the names of the main blood vessels to and from the heart?

Blood comes to the heart via:

• Pulmonary veins (from the lungs)

• Vena cava (from the body)

Blood goes from the heart via:

• Pulmonary artery (to the lungs)

• Aorta (to the body)

What are the names of the main blood vessels to and from the lungs?

Blood comes to the lungs via:

• Pulmonary artery

Blood leaves the lungs via:

• Pulmonary vein