Sometimes when anyone eats hurriedly, talks, laughs or does another similar activity while eating, the flap such as valve, epiglottis closing the passage of windpipe remains open. Thus, the food may enter the wind pipe and coughing helps to clear it. Pharynx is a common passage for food and air. This is a place which has openings for both food pipe and windpipe. A cartilaginous flap called epiglottis prevents the entry of food into the wind pipe by covering the opening of windpipe during swallowing.