A Few More Tasty Tid Bits of Information on the Upper Limbs!

Extensors of the Forearm

The extensor carpi radialis brevis is a short, wide, flattened muscle.  It arises from the humerus and narrows into a long, flat tendon about two-thirds of the way down the arm.  It lies between the extensor carpi radialis longus and the extensor digitorum along the outer surface of the radius.  This muscle extends and radially deviates the hand at the wrist joint.  The extensor carpi radialis longus is a short, flat muscle that arises from the humerus and extends down the arm.  This muscle helps to extend and radially deviate hand at the wrist.  It also helps flex the elbow joint.  The extensor carpi ulnaris is a superficial muscle on the forearm.  It is a narrow, elongated, flattened muscle that extends from the humerus to the dorsal aspect of the fifth metacarpal.   This muscle helps extend the wrist.  The extensor digiti minimi is a small, slender muscle that originates from the humerus and lies between the extensor digitorum and the extensor carpi ulnaris.  At the wrist, the muscle develops a double tendon, which inserts at the extensor expansion of the fifth digit.  The extensor digitorum is a wide, lateral muscle group that extends from the humerus and towards the lower half of the forearm and develops into four tendons that insert into the middle and distal phalanges of the fingers.  It does not insert into the thumb.  This muscle works to extend all the joints of the fingers.  It also extends the wrist.  The extensor indicis is located deep in the forearm, where it originates from the back of the ulna.  At the wrist it develops into a tendon that extends along the back of the hand with the extensor digitorum and inserts in the index finger.  It extends and adducts the index finger.

            A common injury to this muscle group is Elbow Tendinitis (also known as tennis elbow).  This injury occurs from repetitive use of the superficial extensor muscles.  The pain associated with this injury is felt along the lateral epicondyle down the posterior surface of the arm.  With this injury, simple tasks such as opening a door or lifting a book can be painful. 

Proximal end of the humerus

The humerus is the largest bone in the upper limb.  It contains several protrusions and processes.  The anatomical neck of the humerus provides the attachment of the gleno- humeral capsule.  The greater and lesser tubercles are the junction of the head and neck and are the attachment point to several scapulo-humeral muscles.  The interterbicular groove is the separation point of the greater and lesser tubercles and is the protective passageway of the tendon of the biceps brachii. 

Fractures to the proximal end of the humerus are common.  These fractures occur at the neck of the humerus and are common in elderly patients, especially those with osteoporosis.  It is common that the fracture becomes impacted due to a piece of the fractured bone being stuck into the spongy bone.  Due to the fractured area being impacted, the individual can still have stable movement and little pain. 

 

Clavicle

The clavicle is an important connection site between the upper limb and the trunk of the body.  It has two ends, the sternal end and the acromial end.  These ends allow attachment to the sternum and acromion of the scapula, respectively.  The clavicle gives the upper limb the ability to have a free range of motion by keeping it as far away from the trunk as possible.  In addition, it also provides more range of movement for the scapula via the scapulothoracic joint.  It also assists in the elevation of the ribs for inspiration, and provides a protective boundary for nerves that run to the upper limbs. 

            Fracturing the clavicle is one of the most common bone injuries in the body.  In fracturing the clavicle, a domino effect occurs in this region.  With the clavicle fractured, the trapezius can no longer hold up the lateral fragment, causing the upper limb to drop.  However, luckily the strong corococlavicular ligament usually keeps the AC joint from dislocating. 

Information Source:

Clinically Oriented Anatomy