Where do external intercostal muscles originate from?

The external intercostal muscles originate from the lower border of the ribs. These muscles run in a downward and forward direction between adjacent ribs, allowing for the elevation of the rib cage during inhalation. Their primary function is to assist in expanding the thoracic cavity, which increases lung volume and facilitates breathing.

The anatomical arrangement of these muscles, starting from the lower border, enables them to effectively pull the upper rib upward when they contract. This action is essential for the mechanics of respiration, particularly during deep breaths or physical exertion, as it aids in the expansion of the thoracic cavity.

Understanding the origin of the external intercostals helps clarify their role in respiratory mechanics and highlights the importance of each muscle's anatomical positioning in facilitating effective breathing patterns.