Effects of High Blood Pressure on the Vessels

The blood is pumped by the heart through "pipes" into every remote corner of the body. These pipes are called vessels. They differ into arteries and veins. Arteries are the vessels that carry oxygen-rich blood from the heart to its destination. They are subjected to more stress from the pressure generated by the heart pump than veins. Veins transport the blood that has "delivered" nutrients and oxygen at the destination (thus now oxygen-poor) back to the heart.

Our vessels, both arteries and veins, are similar in structure. Both consist of three layers:

• The innermost layer ensures optimal exchange of nutrients and oxygen between blood and vessel wall. It consists of flat cells (endothelium) and connective tissue.
• The middle layer consists of smooth muscle cells, collagen, and elastic fibers. It regulates the width of the vessel through muscle contractions.
• The outermost layer consists of elastic networks formed from collagen fibers. It encloses the vessel from the outside, anchors it in the surroundings, and houses nerves and supplying blood vessels.

Arteries are structurally stronger and thicker than veins. Veins have thinner vessel walls and can expand more easily than arteries. Some veins are equipped with venous valves that prevent blood from flowing back into the extremities. This ensures the return flow to the heart.
However, blood pressure primarily affects the arteries. They can withstand the pressure of the heart by allowing particularly the arteries close to the heart to expand elastically and compensate for the pressure drop during the heart's relaxation phase through contraction (tightening).

However, if there is a persistent high blood pressure on the arteries, they become damaged. Specifically, in the aorta, which is closest to the heart, bulges can occur - known as aneurysms. In this case, the vessel wall can no longer withstand the pressure and forms expansions. Since the vessel wall at these points no longer has the normal strength, the risk of the vessel rupturing at this point is significantly increased.

There are different types of aneurysms: saccular, fusiform, dissecting (the vessel wall is split - bleeding occurs between the wall layers), and false aneurysms. In the case of a false aneurysm, a tear in the vessel wall occurs due to a blunt or sharp injury. The surrounding tissue can limit the resulting hematoma and thus delay bleeding in the event of injury to large arteries. However, this usually only works temporarily. Since this "aneurysm" forms outside the vessel wall, it is called false or spurium.

However, small damages to the innermost layer of the arteries can also occur. This allows blood lipids (for example, cholesterol) and inflammatory cells to stick and form so-called plaques. This is an ongoing process that increasingly narrows the blood vessel and restricts blood flow. The vessel loses its elasticity and hardens (arteriosclerosis). The ability to compensate for changing pressure conditions is lost, and thus blood pressure rises. In the further course, the plaques, which are only covered by a thin layer of endothelium, can break through the layer into the interior of the vessel. To repair this, platelets immediately deposit at this point. This can be compared to an external wound, where a scab forms to close the wound. The same happens now in the vessel: The platelets clump together and form a thrombus (blood clot). If the vessel is already severely narrowed due to arteriosclerosis or the thrombus is large enough, it can completely occlude the vessel. However, it can also detach, get stuck at another narrowing, and occlude the vessel there.

As a result, there is no longer any blood flow to the region supplied by the downstream vessels after the occlusion.
Depending on where in the body this occurs, serious consequences arise from this occlusion, such as heart attack, stroke, kidney failure, and the like.

• http://www.onmeda.de/anatomie/blutgefaesse.html
• http://www.medizinfo.de/kardio/hypertonie/folgen.shtml
• https://www.netdoktor.de/krankheiten/aneurysma/

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