FACTS & HINTS
HIGH-YIELD FACTS
Anatomic Points
Functional Overview
The upper limb is highly mobile and characterized by its ability to perform a wide range of controlled movements to manipulate the surrounding
environment. It is suspended from the trunk at the shoulder, and its stability has been sacrificed to gain mobility. Clinically the limb is divided into
four regions: pectoral girdle, arm, forearm and hand.
Upper Limb Development
The upper limb buds from the embryonic trunk and rotates 90 degrees laterally, such that in the anatomic position, the ventral structures face
anteriorly and the dorsal structures posteriorly. This contrasts with the medial rotation of the lower limb. Thus, the upper and lower limbs are 180
degrees out of phase. Flexors of all joints in the upper limb are anterior, and extensors are posterior.
Clinical Points
Winged Scapula
Normally the scapula is held closely against the posterior thoracic wall. Damage to the long thoracic nerve to serratus anterior (which
courses superficially over the muscle) causes "winging" of the scapula as its medial border lifts away from the thorax when the arm is
raised. This is accentuated when the individual leans on the hand or pushes the upper limb against a wall. Most importantly, the arm cannot
be abducted above the horizontal plane because glenoid cavity cannot be rotated upward without the action of the serratus anterior.