ELASTIC MATERIAL IN THE AORTA
A site that contains a large amount of elastic material is the wall of the aorta and the wall of the beginning of its most important branches.
A cross-section of the aorta shows in its middle part (tunica media) a large amount of lines of material that stains positively for elastic fibers. These lines are parallel one to another and concentric with respect to the aortic lumen. These lines are in fact plates of elastic material. They are therefore not fibers, but their composition is similar to that of the elastic fibers seen previously.
The figures show regions of the aortic wall at three different magnifications. Observe the cross sections of the plates of elastic material.
See the important role of this large amount of plaques:
– after each systole (contraction), the heart releases a certain volume of blood into the aorta;
– at this moment the wall of the aorta dilates;
– after the blood has passed through, the wall returns to its previous size thanks to the elastic material of its walls, until the next systole occurs.
As a result, after each systole there is a certain increase in blood pressure (systolic pressure) which soon returns to a lower level (diastolic pressure).
What would happen if the wall of the aorta did not go through this cycle of giving way, dilating and returning to its previous size:
– the blood flow would behave as if it were inside a tube with rigid walls, such as a plastic tube that carries water. The pressure in the aorta would rise significantly after systole and fall significantly during diastole. In the remaining arteries and capillaries of the whole circulatory system, the blood would advance in leaps and bounds from systole to systole, instead of maintaining the continuous flow provided by the elasticity of the aorta wall.
A cross-section of the aorta shows in its middle part (tunica media) a large amount of lines of material that stains positively for elastic fibers. These lines are parallel one to another and concentric with respect to the aortic lumen. These lines are in fact plates of elastic material. They are therefore not fibers, but their composition is similar to that of the elastic fibers seen previously.
The figures show regions of the aortic wall at three different magnifications. Observe the cross sections of the plates of elastic material.
See the important role of this large amount of plaques:
– after each systole (contraction), the heart releases a certain volume of blood into the aorta;
– at this moment the wall of the aorta dilates;
– after the blood has passed through, the wall returns to its previous size thanks to the elastic material of its walls, until the next systole occurs.
As a result, after each systole there is a certain increase in blood pressure (systolic pressure) which soon returns to a lower level (diastolic pressure).
What would happen if the wall of the aorta did not go through this cycle of giving way, dilating and returning to its previous size:
– the blood flow would behave as if it were inside a tube with rigid walls, such as a plastic tube that carries water. The pressure in the aorta would rise significantly after systole and fall significantly during diastole. In the remaining arteries and capillaries of the whole circulatory system, the blood would advance in leaps and bounds from systole to systole, instead of maintaining the continuous flow provided by the elasticity of the aorta wall.
Aorta. Staining: Weigert. Low, medium, large magnification.