3. 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
4. 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
5. 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
6. Purpose of artery
• The arteries
1. deliver the oxygen-rich blood to the capillaries
2. the actual exchange of oxygen and carbon
dioxide occurs
8. 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
9. 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
10. Purpose of vein
• Valves that are located inside the veins
• The valves are like gates that only allow traffic
to move in one direction
11. Purpose of vein
• Vein valves
1. to keep blood flowing toward the
heart
2. to allow blood to flow against the
force of gravity.
12. 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.
14. Capillary
• Capillaries
1. very thin
2. Fragile
3. one epithelial cell thick
4. blood cells can only pass through them in single file
15. 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.
16. 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
17. 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
