Elbow & Forearm. Notes. Notes. Lecture Slides - A.D.A.M. Lab Pics. Bones & Joints: Elbow & Forearm

Transcription

1 Elbow & Forearm Elbow & Forearm Notes Lecture Slides - A.D.A.M. Lab Pics Notes Bones & Joints: The elbow joint is a combination of joints but common reference is usually to the articulation of the distal humerus with the two forearm bones - radius and ulna. Medially the "elbow" is the trochlea of the humerus with the matching notch of the ulna (ulnotrochlear joint). Laterally it is the articulation of the capitulum of the humerus with the matching cup in the radial head (radiocapitular joint). Together they share one capsule and are considered a hinge joint as the specific type of synovial joint - just as the shoulder is a ball-and-socket type synovial joint. The movements are flexion/extension around a side-toside axis. Forearm joints are the proximal and distal radioulnar joints. The proximal is actually within the elbow joint capsule just described and consists of the radial head spinning within the matching notch of the proximal ulna. The distal is associated with the wrist joint capsule and consists of the ulna head around which the radius spins. Make sure to review the bones on either the McMinn or the A.D.A.M. CD.

2 elbow: Joint Classification Movements Possible & Comments ulnotrochlear synovial: together considered a hinge joint flexion/extension (s-s axis/sagittal plane) radiocapitular forearm: proximal and distal radioulnar joints synovial: both are pivot joints in which the radius pivots within the ulnar notch proximally and around the ulnar head distally pronation/supination (up-down axis/horizontal plane) Lecture Slides Following info is on elbow and forearm muscles - muscles running mostly from the (A) proximal or mid humerus, crossing the elbow joint, and attaching to one of the forearm bones - moving the forearm at the elbow joint into either flexion of extension; (B) from the distal humerus to either the radius or ulna causing pronation or supination. (While attachments are listed below, the McMinn CD has illustrations of the exact attachments. It isn't necessary that you see this, but it might help. Can see the same in lab on the painted skeletons.)

3 Left Distal Humerus - Anterior View A - Medial epicondyle B - Trochlea C - Capitulum D - Lateral Epicondyle Biceps Brachii Prox Attachment: supraglenoid tubercle of scapula (long head); corocoid process (short head) Distal Attachment: proximal radius, between radius and ulna Action: elbow flexion, shoulder flexion, forearm supination Innervation: Musculocutaneous n. (C5, 6)

4 Brachialis Prox Attachment: Anterior humerus Distal Attachment: Proximal anterior ulna Action: Flexes forearm Innervation: Musculocutaneous n. (C5, 6) Triceps Brachii (long head in red; lateral head just to the right of long head; medial head not shown) Prox Attachment: Infraglenoid tubercle of scapula (long head), lateral and medial humerus (lat and med heads) Distal Attachment: All three heads into the olecronon of the ulna Action: Both - Extension of the forearm; shoulder extension via long head Innervation: Radial n. (C6, 7, 8)

5 Brachioradialis (A) Prox Attachment: Distal lateral humerus Distal Attachment: Distal lateral radius Action: Elbow flexion; forearm supination and pronation Innervation: Radial n. (C5-6) Pronator Teres (B) A.D.A.M. Sofware, Inc. Prox Attachment: Medial epicondyle of humerus Distal Attachment: lateral mid radius Action: Forearm pronation (also elbow flexion) Innervation: Median n. (C6, 7) Pronator Teres (A) Supinator (B, in red) Prox Attachment: Lateral epicondyle of humerus Distal Attachment: lateral mid radius proximal to pronator Action: Forearm supination Innervation: Radial n. (C5, 6)

6 Supinator (posterior view) Here shown wrapping around the radius Lab Pics Biceps Brachii - anterior view of the left UE A is short head to corocoid process of scapula B is long head passing through bicipital groove C is deeper brachialis D is brachioradialis All are anterior to side-to-side axis for elbow flexion/extension = all function as elbow flexors.

7 Here the forearm has been pronated, winding the biceps tendon zround the radius, in between the radius and ulna. The arrow show the direction of pull of the biceps when it contracts to supinate the arm out of the pronated position. The green line represents the axis for supination/pronation. Brachioradialis - looking at the forearm in neutral supination/pronation - hand is at the bottom Brachioradialis (yellow) pulls parallel to pro/sup axis and has no effect on pronation or supination in this neutral position of the forearm.

8 Here the forearm has been supinated (passively). The yellow arrow represents the pull of the brachioradialis crossing the axis to pronate the forearm to neutral from this supinated position. A is the distal end and attachment of the biceps brachii. B is the pronator teres. Here the forearm has been pronated (passively). Brachioradialis (yellow) crosses the axis to supinate the forearm to neutral from this pronated position. As above, A is distal end of the biceps brachii; B is the pronator teres.

9 Pronator Teres The forearm is at rest in a supinated position; contraction of pronator (yellow) crosses the axis, and is anterior to it, so pronates the forearm. Supinator The forearm has been passively moved into a pronated position; contraction of supinator (yellow arrow) crosses the axis (blue) in a posterior relationship and supinates the forearm (as seen below). Supinator has shortened through contraction and forearm is now supinated. Triceps Brachii - Posterior view of left arm Triceps contraction (yellow arrow) shown crossing the s-s axis for flexion/extension. It is posterior to the axis, attaching to the ulna, and, therefore extends the forearm at the elbow.