The upper limb is modified for prehension and tactile sensibility. Part of the adaptation for prehension is increased movement at the joints, often at the expense of stability. The “working tool” i.e. the hand is positioned at the end of a long strut with a freely mobile base (the shoulder joint complex) and two foldable members (the arm and forearm).
This shoulder joint complex allows a wide range of movement on account of the following factors:
Shallow glenoid cavity which accommodates only ½ the head of the humerus.
Laxity of the capsule of the glenohumeral joint.
Replacemnt of strong ligaments by a musculotendinous “cuff” (Rotator cuff) – often referred to as ligaments of variable tension
A synovial highly movable sternoclavicular joint.
Presence of a long clavicle that holds the upper limb away from the trunk.
The upper limb is modified for prehension and tactile sensibility. Part of the adaptation for prehension is increased movement at the joints, often at the expense of stability. The “working tool” i.e. the hand is positioned at the end of a long strut with a freely mobile base (the shoulder joint complex) and two foldable members (the arm and forearm).