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If you have ever had a phone or music player stop working after you have been using it for a while, you know that things can wear down with time. The same thing happens to the human body, except in this case it's a much more serious problem than trying to figure out how you're going to get your iTunes fix. Heart valves can become problematic over time. When this happens it can be extremely harmful. A heart valve can have stenosis, which occurs when the valve no longer open as widely as it would normally. It can also become leaky, which means that blood can backflow into chambers that it should have already been pumped from. If you are trying to get ketchup out of a bottle when the tip is plugged, you know that you have to work extra hard to get the desired effect. This is exactly what the heart has to do to get all of the oxygen and nutrients required to the rest of the body. If it has to work too hard for too long, the heart can fail.
When valves begin to become problematic, they must be replaced. Many advances have been made in life saving valve replacement technology. Pig heart valves were discovered to be very similar to those of human hearts. The first successful valve xenograft (meaning a tissue implantation from one species to another) occurred in 1965. Since then, heart valves from pigs, horses, and cows have been utilized extensively to replace ailing heart valves throughout the world.
The major setback with using heart valves from other species is that the human body's immune system rejects foreign objects. This makes the replacement valves useless after a period of time. Recent attempts that have shown some success in alleviating these problems include using xenograft valves that have had all of the cells removed, leaving behind just the matrix. No, not that matrix. This allows the valve recipient's cells to replace the missing cells and avoid rejection of the valve. It's a win-win—maybe not for the animal that donated the valve.
Do you think your pet is the best animal in the entire world? You are not alone. People have been comparing animals since they were first domesticated. Many people believe that the only way to really determine which animals is truly better is to have a competition. Today, animals compete in racing, polo, rodeo, shows of training, and fighting (although this has been outlawed in many countries).
Animal racing is the most prevalent type of animal competition. Dogs, horses, and pigeons are among the most popular racing animals throughout the world. However, racing competitions can involve a variety of animals including: armadillos, buffalo, camels, cockroaches, frogs, hamsters, lizards, mice, ostriches, pigs, porcupines, snails, turtles, and yaks.
Violent or deadly animal competitions of yesteryear have largely been replaced by more humane contests such as Camel wrestling and Elephant polo which rarely lead to injury. Animal breed standard competitions are a particularly longstanding tradition. The Westminster Kennel Club Dog Show has been held since 1877 and is often watched around the world. Cat and rabbit shows are also popular amongst cat and rabbit lovers. Some animals have even been seen trying their paws at human sports as well.
Carbon monoxide is a colorless, odorless, and tasteless gas. It is toxic to humans, and in lower doses it can cause headaches and flu-like symptoms. There is a slight danger of carbon monoxide poisoning in residential homes, especially during the winter months because the home is sealed, and the furnace is on. A faulty furnace can release carbon monoxide. As a result, many states suggest having carbon monoxide detectors inside your home.
Carbon monoxide is also a danger when working in coal mines. Before the days of manufactured carbon monoxide detectors, coal miners knew that certain animals could act as living carbon monoxide detectors. Canaries and mice were often used, although canaries were the primary choice. Their small size and fast rate of respiration makes them more susceptible to the gas than humans, and they can act as an early warning system. Canaries will exhibit stressed behavior at low levels of carbon monoxide. At high levels, they will fall off of their perch. The first person into the mine would carry the canary cage. If the canary started acting oddly, miners knew to evacuate immediately or to put on a ventilator mask. Canaries were still officially used in British mines until the end of 1986 when official detection devices replaced them. Although canaries are no longer used in coal mines, the phrase, "canary in a coal mine" is still used to describe something that is a predictor of danger to come.