Question

Complete each sentence by dragging the proper label into the appropriate position. The ____ is the first vessel blood enters upon exiting the heart. The ____ expand and recoil with every heart beat due to a histologically dominant network of elastic tissue in the tunica media. Just prior to entering capillary beds, ____ have become extremely thin and present only a few layers of smooth muscle. The site of gaseous exchange, or ____, are characterized by extremely thin walls with only endothelium and basal lamina, which better suits diffusional requirements. After exiting the capillary, ____ contain no muscle and are the first vessel that blood enters on its way back to the heart. The ____ contain abundant but irregularly spaced smooth muscle with frequent valves present in the tunica interna. The superior vena cava is an example of a ____ that includes smooth muscle circularly and longitudinally arranged in the tunica media and , respectively.

Answer 1

Answer:

1. The aorta is the first vessel blood enters upon exiting the heart.

2. The large (elastic) arteries expand and recoil with every heartbeat due to a histologically dominant network of elastic tissue in the tunica media.

3. Just prior to entering capillary beds, arterioles have become extremely thin and present only a few layers of smooth muscle.

4. The site of gaseous exchange, or capillaries, are characterized by extremely thin walls with only endothelium and basal lamina, which better suits diffusional requirements.

5. After exiting the capillary, venules contain no muscle and are the first vessel that blood enters on its way back to the heart.

6. The medium veins contain abundant but irregularly spaced smooth muscle with frequent valves present in the tunica interna.

7. The superior vena cava is an example of a large vein that includes smooth muscle circularly and longitudinally arranged in the tunica media and externa respectively.