Yes there are two one to prevent reflux at the the bottom where it connects to the stomach and one at the top which stops are feom going to the stomach and food from going into your lungs (Sauce ) .

According to the Wikipedia article there are 50 types/kinds but I haven't found how many we can control. One of the most important though is the urethral sphincter which controls urine exiting the body (or sperm in people that produce it).