Blood Vessels

Artery

Artery• tough on the outside and smooth on the inside

• has three layers:

1. an outer layer of tissue

2. a muscular middle

3. an inner layer of epithelial cells

In the artery..• The muscle in the middle

1. Elastic

2. Very strong

• The inner layer

1. very smooth so that the blood can flow easily with no obstacles in its path

• The muscular wall of the artery

helps the heart pump the blood

What happens in the artery?

• When the heart beats, the artery expands - it fills with blood

• When the heart relaxes, the artery contracts, exerting a force - strong enough to push the blood along

Purpose of artery

• The arteries

1. deliver the oxygen-rich blood to the capillaries

2. the actual exchange of oxygen and carbon dioxide occurs

Vein

Vein

• Veins transport blood at a lower pressure

• Veins have three layers:

1. an outer layer of tissue

2. muscle in the middle

3. a smooth inner layer of epithelial cells

However, the layers are thinner, containing less tissue

Purpose of vein..

• Veins receive blood from the capillaries after the exchange of oxygen and carbon dioxide has taken place

• The veins transport waste-rich blood back to the lungs and heart

• Waste-rich blood

1. keeps moving in the proper direction

2. not be allowed to flow backward

Purpose of vein

• Valves that are located inside the veins

• The valves are like gates that only allow traffic to move in one direction

Purpose of vein

• Vein valves

1. to keep blood flowing toward the heart

2. to allow blood to flow against the force of gravity.

Purpose of vein

• Blood that is returning to the heart from the foot has to be able to flow up the leg.

• The vein valves

1. provide footholds for the blood as it climbs its way up.

Capillary

Capillary

• Capillaries

1. very thin

2. Fragile

3. one epithelial cell thick

4. blood cells can only pass through them in single file

In the capillary..• Red blood cells inside the capillary

1. release their oxygen which passes through the wall

2. into the surrounding tissue

• The tissue releases its waste products (CO2 )

1. which passes through the wall

2. into the red blood cells.

Purpose of capillary

1. Arteries pass their oxygen-rich blood to the capillaries

2. Capillaries then pass their waste-rich blood to the veins for transport

3. Back to the heart

Purpose of capillary

• Capillaries are also involved in the body's release of excess heat

• For example, your body and blood temperature rises

• To help release this excess heat, the blood delivers the heat to the capillaries which then rapidly release it to the tissue

Heart blood circulation

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