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A Closer Look at Blood Vessels

A Closer Look at Blood Vessels. Key Concepts What are the structures and functions of arteries? What are the structures and functions of capillaries and veins? What causes blood pressure?. Key Terms. Coronary artery Pulse Diffusion Blood pressure. Blood vessels.

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A Closer Look at Blood Vessels

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  1. A Closer Look at Blood Vessels Key Concepts What are the structures and functions of arteries? What are the structures and functions of capillaries and veins? What causes blood pressure?

  2. Key Terms • Coronary artery • Pulse • Diffusion • Blood pressure

  3. Blood vessels • Blood vessels can be as wide as your thumb, but most are much finer than a human hair • If all were hooked together end to end they would stretch almost 100,000 kilometers – long enough to wrap around the earth twice, with a lot left over!

  4. Arteries When blood leaves the heart it travels through arteries Aorta is the largest artery in the body Aorta soon branches into smaller arteries First branches called the coronary arteries – go to the heart muscle itself to supply the heart with O2 and nutrients Others branch out to brain, intestines and other organs

  5. Artery Structure • Walls are generally very thick, consist of three layers • Innermost layer is made of epithelial cells and is smooth – lets blood flow freely • Middle layer is muscle tissue • Outer wall made of flexible connective tissue • Arteries have both strength and flexibility to withstand the tremendous pressure of blood as it is pumped by the heart

  6. Pulse • Caused by the alternating expansion and relaxation of the artery wall. • Every time the heart’s ventricles contract, they send a spurt of blood out through arteries. It pushes on the artery wall and makes them expand, After the spurt of blood passes the artery wall becomes narrower again • When you count the number of times an artery pulses, you are determining how fast the heart is beating.

  7. Regulating Blood Flow • Layer of muscle in an artery acts as a control gate, adjusting the amount of blood sent to different organs • When the muscle contracts the opening of the artery becomes smaller. When it relaxes the opening becomes larger • The arteries leading to areas that need more blood relax and open up allowing more blood to flow through

  8. Capillaries • Blood flows through smaller and smaller arteries until it gets to extremely thin-walled blood vessels known as capillaries • Only room for 1 cell at a time • Transferring O2 and food to cells and taking CO2 and other wastes from cells occur in capillaries. This happens by diffusion

  9. Veins • After capillaries blood starts its journey back to the heart • Enters blood vessels known as veins • Veins have 3 layers like arteries, but veins are thinner walled than arteries • Pushing force of the heart is much less in veins • Contraction of skeletal muscles help the blood return to the heart • Valves help the blood from flowing backwards • Breathing movements squeeze against veins and force blood towards the heart

  10. Blood Pressure • Pressure is the force that something exerts over an area • Blood exerts a force called blood pressure against the walls of blood vessels • Blood pressure is caused by the force with which the ventricles contract • As blood moves away from the heart, blood pressure decreases • Blood flowing near the heart arteries exerts the highest pressure

  11. Measuring Blood Pressure • Blood pressure is measured with an instrument called a sphygmomanometer • Cuff is wrapped around the person’s arm and inflated until blood flow from the artery is stopped • The examiner listens to the pulse and records 2 numbers. • Pressure when the ventricle contracts and the pressure when the ventricle relaxes • The 2 numbers are expressed as a fraction • 120/80 or lower is typical for a healthy adult

  12. Sources • http://www.landholt.com/Graphics/Images/arteries_veins_01.jpg

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