A mule is the result of a horse that has been bred with a donkey. Mules are generally sterile, meaning that they cannot be bred with each other in most cases. They also have 63 chromosomes. In appearance, mules may look very similar to donkeys. They also have stiff hair. Much like donkeys, mules are strong animals and tend to have calmer personalities.
Air Embolism. An air embolism is an obstruction in a vein or artery caused by a bubble of gas. Air enters the circulatory system when the pressure gradient favors movement of air or gas from the environment into the blood. A venous air embolism is the most common form of air embolism.
Smoking is the most common cause of a serious lung condition called emphysema. With emphysema, the air sacs (alveoli) weaken and lose their ability to contract after expanding. Air can also get trapped in these sacs, causing some to break. This can make breathing difficult and ultimately decrease the amount of oxygen you get into your blood stream.