Structure/Morphology
The external intercostal membrane (anterior intercostal membrane) is the thin aponeurosis that arises from the anterior end of the external intercostal muscles. Its fibers travel inferomedially, parallel to those of the external intercostal muscles, and are attached to the superior and inferior borders of costal cartilages and the sternum.
Anatomical Relations
The external intercostal membrane is found within the intercostal spaces of the costal cartilages, where it extends from the sternal ends of the ribs to the anteromedial ends of the intercostal spaces.
It is located:
- superficial to the internal intercostal muscles;
- deep to the pectoralis major and external abdominal oblique muscles;
- medial to the external intercostal muscles;
- lateral to the sternum.
Function
The external intercostal membrane provides structural support to the intercostal spaces that are located between the costal cartilages.
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Intercostal Muscle
The intercostal muscles are divided into the external group, fibres of which run in a caudal–ventral direction from their upper rib and are deficient anteriorly, and the less powerful internal group which have fibres running caudal–dorsal from their upper rib and are deficient posteriorly.
