In: Biology
Epiglottis is the structure which prevents the entry of water and food into the lungs. In some cases people may eat or drink in careless manner or in a hurry, which may cause water or some food particles to go pass the epiglottis and enter the lungs.
The presence of fluid or water in the lungs makes it difficult to function. The presence of water in the alveoli of the lungs makes it difficult for carbon-di-oxide and oxygen molecules, as these molecules have to travel a great distance. This makes transfer of gasses between lungs and blood stream impossible. This condition leads to absence of oxygen in the blood, known as Pulmonary Edema (shortness of breath).
In normal scenario, air passes through mouth and nose, to reach trachea and into the bronchial tubes. These bronchial tubes gets branched into smaller segments to reach alveoli. In alveoli, air gets sepearted from RBC (Red blood cells) with the help of alveolus.