The Great Rift Valley and smoking
Viewed from outer space, the one thing that is very distinct about the earth is the Great Rift Valley. Named by a 19th Century British explorer, the rift valley is a wide trench that begins in northern Syria and runs 6,000km through Kenya to Tanzania. The rift valley exists because of the movement of the earth’s attempts to create new tectonic plates. A rift is, as the name suggests, an area where the earth’s surface has fractured and two plates slowly move apart from each other. The space left in between is filled with molten magma, which oozes from deep within the earth’s crust.
When this movement happens rapidly we have an earthquake. When it happens very slowly we have East African Rift Valley. One day the Nubian plate, which is what the western part of Kenya is sitting on, will separate from the Somali plate; which is what Somalia and the eastern part of Kenya is sitting on. Eventually Somalia will be an island. Some people might have an opinion about this, but it is happening very slowly and it is unlikely that in your grandchildren’s lifetime that you will see much difference in the Rift Valley. However there are two good reasons to pay attention to this phenomenon. First, as the plates are being created geothermal energy is being released, generating electricity for us. Secondly, the process mimics an aortic aneurysm.
The largest artery in the body is the aorta. It is about 30cm long and about 2.5cm in diameter - the thickness of a garden hose. Beginning from the left side of the heart it rises up curving over the heart and dividing into four. The bit that rises to the top of the heart is called the ascending aorta. The coronary arteries are branches of this part of the aorta. As it comes over the heart, the name changes to the aortic arch. It is here where it gives off the arterial branches that supply the head, neck and arms. The aorta then descends down in to the chest proper where as the descending thoracic aorta it gives off branches that supply the ribs. The main vessel continues into the abdomen. As it passes through the diaphragm its name changes again. As the abdominal aorta it splits into two even branches that eventually will go into each leg, but not before the major abdominal organs such as the liver are supplied with blood.
Just like any other artery the aorta has a thick wall. Looked at in cross-section, three layers can be identified. The innermost layer is smooth, providing the necessary surface for blood to flow. In the middle there is a layer of muscle and elastic fibre that allows the aorta to expand and contract with each heartbeat. Finally the outer layer, the adventitia, provides a more rigid structure and additional support. It looks just like the rubber garden hosepipes.
Occasionally in some people there can be a bulge in a section of the aorta. A bulge can form anywhere but is more common in the abdominal aorta. The major causes of such a weakness are high blood pressure and atherosclerosis (high cholesterol in layman’s terms). Sometimes the cause is not known and a person can be born with an area of weakness. Whether that is the case or there is a known cause, the bulge can rupture because the stretched area is weak and thin like a stretched balloon. Because the aorta carries so much blood, the result of a ruptured aorta is often death.
Even when it is not ruptured an aneurysm causes problems. The bulge behaves like a pothole, slowing down blood flow, which then starts to clot. Blood clots that break off from an aortic aneurysm in the abdomen can block blood flow to the belly or legs or even in the brain or heart leading to a stroke or heart attack. Unless it forms a clot or ruptures an aneurysm rarely have symptoms. Sometimes they are discovered during routine medical examinations or when the doctor is examining a patient for some other condition.
When a rupture has occurred treatment is emergency surgery to repair the aorta. If it has not occurred but has been discovered then treatment consists of reducing the risk factors. Apart from high blood pressure and atherosclerosis, tobacco smoking is the other major risk factor. So even though it looks from afar like the geothermal springs it is very different and there really is no benefit to smoking, only harm.