|Structures - Arm and Forearm|
Brachial intermuscular septa
- Extend from the brachial fascia, a portion of the deep fascia, enclosing the arm.
- Consist of medial and lateral intermuscular septa, which divide the arm into the anterior compartment (flexor compartment ) and the posterior compartment (extensor compartment).
- Is a V-shaped interval on the anterior aspect of the elbow that is bounded laterally by the brachioradialis muscle and medially by the pronator teres muscle.
- Has an upper limit that is an imaginary horizontal line connecting the epicondyles of the humerus with a floor formed by the brachialis and supinator muscles.
- Has a lower end where the brachial artery divides into the radial and ulnar arteries, with a fascial roof strengthened by the bicipital aponeurosis.
- Contains (from lateral to medial) the Radial nerve, Biceps tendon, Brachial artery, and Median nerve.
Interosseous membrane of the forearm
- Originates from the medial border of the biceps tendon.
- Lies on the brachial artery and the median nerve and passes downward and medially to blend with the deep fascia of the forearm.
- Is a broad sheet of dense connective tissue that extends between the radius and the ulna. Its proximal border and the oblique cord (which extends from the ulnar tuberosity to the radius) form a gap through which the posterior interosseous vessels pass.
- Is pierced (distally) by the anterior interosseous vessels.
- Provides extra surface area for attachment of the deep extrinsic flexor, extensor, and abductor muscles of the hand.
|Characteristics of the arm and forearm|
Pronation and supination
- Is formed laterally by the axis of the arm and forearm when the elbow is extended, because the medial edge of the trochlea projects more inferiorly than its lateral edge.
- Is wider in women than in men and disappears when the forearm is flexed or pronated.
- Occur at the proximal and distal radioulnar joints and have unequal strengths, with supination being stronger.
- Are movements in which the upper end of the radius nearly rotates within the annular ligament.
- Supination - The palm faces forward (lateral rotation).
- Pronation - The radius rotates over the ulna, and thus the palm faces backward (medial rotation about a longitudinal axis, in which case the shafts of the radius and ulna cross each other).
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