Anatomy for MRCEM primary exam

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Upper limb Anatomy

Pectoralis Major muscle

Surface markings, actions and nerve supply of Pectoralis major

OriginClavicle, aponeurosis of the abdominal external oblique muscle, Sternum + upper 6 costal cartilages
InsertionLateral lip of Bicipital groove of Humerus
Nerve supplyMedical and Lateral Pectoral nerves
ActionsFlexion, Adduction and Medical rotation of arm
Pectoralis major Origin and insertion

Pectoralis major Origin and Insertions – Image modified from BodyParts3D, © The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan

The Pectoralis Major muscle makes the bulk of chest muscles. It originates from 3 different zones – Clavicular, Abdominal and Sterno-costal. Check the images above.

Regarding actions, if the muscle contracts what happens to the Humerus? As it’s attaching on the front side of bone, you’ll expect some rotation to happen.