The external intercostal membrane is a structure that sits between the ribs and plays a crucial role in breathing. It is also known as the external intercostal muscle, external intercostal space, or external intercostal layer. The external intercostal membrane helps to raise the rib cage during inhalation and lower it during exhalation, aiding in the exchange of oxygen and carbon dioxide. This membrane is made up of tough, fibrous tissue and is located in the spaces between the ribs. Alternative words for this structure include external intercostal fascia, thoracic wall muscle, and lateral thoracic wall membrane. Whatever you choose to call it, the external intercostal membrane is an essential part of the respiratory system.