Key Questions for Understanding the Blood Vessels 1

Key Questions for Understanding the Blood Vessels

1. Three Different Tunics of the Arteries and Veins: o Tunica interna: lines the lumen (interior of the vessel) and is a thin layer of endothelium. It forms a slick surface that decreases friction as blood flows through it

1. Three Different Tunics of the Arteries and Veins: o Tunica media: bulky middle coat made of smooth muscle and elastic tissue. This muscle is active in changing the diameter of blood vessels

1. Three Different Tunics of the Arteries and Veins: o Tunica externa: is composed largely of fibrous connective tissue. Its function is to support and protect the vessels

2. Why do arteries have heavier tunica media than veins? o Arteries are closer to the heart, and must be able to expand as blood is forced into them and then recoil passively as blood flows off. Their walls must be strong and stretchy enough to take these changes in pressure. Thus, they have thicker muscle

3. Why do large veins have valves inside their lumens? o To prevent backflow of blood and to ensure that the amount of blood returning to the heart equals the cardiac output

4. How do skeletal muscles aid in venous return? o As the muscles surrounding veins contract and relax, the blood is “milked” through the veins to the heart.

5. What are capillary beds? o Capillary beds are interweaving networks of capillaries that exchange blood between tissue cells

6. What causes varicose veins to form? o When the valves of veins in the legs give way, they cause pooling of blood and inefficient venous return. Veins become twisted and dilated.

7. Why is a continuous supply of blood crucial to the brain? o A lack of blood for even a few minutes causes delicate brain cells to die due to a lack of oxygen

8. How does the circle of Willis protect the brain? o The circle of Willis protects the brain because it provides more than one route for blood to reach brain tissue in case of a clot or impaired blood flow

9. What do the veins of the hepatic portal circulation do? o These veins drain the digestive organs, spleen, and pancreas; and they deliver this blood to the liver. It is unique because hepatic veins feed capillaries in the liver, not arteries

10. What happens to blood in the liver? o The liver processes glucose, fat, and proteins and removes them from the blood for storage, and it later releases them to the blood when they are needed by the body’s cells

11. What blood vessels are contianed in the umbilical cord? o o One umbilical vein carries blood rich in nutrients and oxygen to the developing fetus Two umbilical arteries carry carbon dioxide from the fetus to the placenta