It is much larger than the supraspionous fossa. The portion of the dorsal surface below the spine is called the infraspinous fossa. The portion of the dorsal surface above the spine is called the supraspinous fossa. The acromion forms the cavity of the glenohumeral joint. The spine ends in a process called the acromion. The back of the scapula is divided into two unequal parts by the spine of the scapula. Margo medialis Medial border, parallel to the longitudinal axis of the spine Margo lateralis Lateral, or axillary border Margo superior Superior border Angles īorders of the scapula connect in three angles:Īngulus superior Superior and medial border Angulus inferior Medial and lateral border Angulus lateralis Lateral and superior border Surfaces Dorsal surface When the upper limb is abducted 180°, 60° of those 180 occur by rotation of the scapula and 120° by movement of the humerus itself. The scapula and humerus move in a 1:2 ratio. To move the upper limb above the horizontal plane, the coracoacromial ligament ( fornix humeri) needs to be engaged. Moving any more, the humerus' head would collide with the coracoid process of the scapula.
Moving the upper limb Īs is, the humerus can only move 90° upwards, into the horizontal plane. The scapula protects the thoracic cavity form the dorsal side The scapula is the origin and instertion of various muscles
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