Metaphors and analogies have long been used to turn complex medical concepts into everyday ones, albeit with fancy terminology. Having been involved with many 3D animations on the topics of Blood Pressure, arteriosclerosis, cholesterol and the like, we find that often a metaphor goes a long way to building understanding, credibility and even compliance with patients. One of my favorite analogies is what we call the arterial highway. Much like their tarmacked counterparts, arteries act as conduits for all the parts that make your body go. A city typically uses highways, gas lines, water pipes, railways and other infrastructure to distribute important materials to its people. Your body is much the same, except that it does it all in one system, the cardiovascular system. This is used to deliver nutrients, extract waste, transport and deliver oxygen and even to maintain the temperature!
The arteries can do all these things because of their smart three-layered structure. Our arteries consist of a muscular tube lined by smooth tissue. They have three layers named – the Adventitia, Media and Intima. Each is designed with a specific function and through the magic of evolution has developed to perform its function perfectly.
The first is the Tunica Adventitia, or just adventitia. It is a strong outer covering over the arteries and veins. It has special tissues that are fibrous. The fibers let the arteries flex, expanding and contracting to accommodate changes in blood pressure as the blood flows past it. Unlike a steel pipe, arteries pulsate and so must be at once be flexible, and strong.
Tunica Media - the middle layer of the walls of arteries and veins is made up of a smooth muscle with some elasticity built in. This layer expands and contracts in a rhythmic fashion, much like a Wave at a baseball game, as blood moves along it.
The media layer is thicker in arteries than in veins, and importantly so, as arteries carry blood at a higher pressure than veins.
The innermost layer of arteries and veins is the Tunica Intima. In arteries, this layer is composed of an elastic lining and smooth endothelium - a thin sheet of cells that form a type of skin over the surface. The elastic tissue present in the artery can stretch and return, allowing the arteries to adapt to changes in flow and blood pressure. The intima is also a very smoothe, slick layer so that blood can easily flow past it.
Every layer of the artery has developed evolutionary traits that help your arterial system to maintain flexibility, strength and promote blood flow. Diseases and conditions like high cholesterol or high blood pressure, diabetes and others prevent the arteries from doing their function well by creating blockages or increasing the stress on one or more of the layers. For example, high blood pressure causes rips in the smooth lining of the Intima. Anybody who has experienced a pipe burst in a house knows that the damage can be extreme and can never fully be restored.
Understanding the delicate functions of the arterial structure gives good incentive to treat them better. Conditions like high blood pressure, high cholesterol and lifestyle diseases such as diabetes create tears, holes, blockages, and can disrupt the functions of one or more layers. Getting patients to visualize the effect of bad eating habits on their anatomy helps to increase patient compliance. In modern society, the concept of highways goes hand in hand with the concept of traffic jams. Patients understand that the arterial highway is one that can never be jammed.