Pleural effusion - image description

The illustration shows the lungs in the chest. It shows the windpipe (trachea) coming down from the neck into the chest. About halfway down the chest, the windpipe divides into two tubes. One tube goes into the left lung. The other tube goes into the right lung. There are ribs around the outer side of each lung. Underneath the lungs and going across the body is a muscle called the diaphragm.

Surrounding each lung are two thin membranes. These are called the pleura. The membrane closest to each lung is called the inner pleura. The membrane which lines the chest wall is called the outer pleura. There is a small space between the two layers of the pleura. This space is called the pleural cavity. Fluid has built up between the two layers of the left lung. This means the lung is smaller. The fluid is called a pleural effusion.