Re: Flexor Region of the Forearm: Learning Objectives and Review Questions - 2011

Comments:
: : : Flexor Region of the Forearm: Learning Objectives and Review Questions : : : These questions were not submitted by the lecturer. : : : True/False - 2011 : : The posterior relationships of the medial humeral epicondyle include the ulnar nerve, inferior ulnar collateral artery, and the humeral head of origin of the flexor carpi ulnaris. : : F - superior ulnar collateral artery : Agree. : : The proximal margin of the trochlear notch is contributed by the coronoid process. : : F - distal : Agree. : : The interosseous membrane has fiber directions that resist proximal displacement of the radius. : : F - Wouldn't the distal-medial direction resist distal displacement? : True. The predominate fiber direction is, as you suggest, superior lateral (radius) to inferior medial (ulna). Forces that move the radius proximal are transfered to the ulna and, thus, diverted from the capitulum. : : The interosseous membrane limits forces transmitted to the capitilum. : : T : Agree. : : The styloid process of the ulna has an articular disk mediating articulations between the radius and the scaphoid bone. : : F - There is an articular disk between the radius and the ulna, though it adjoins the medial aspect of the radius. The scaphoid articulates with the distal-lateral aspect of the radius. : Agree. Triquetrum. See Gray's and upcoming lectures for triangular fibrocartilage complex (TFCC). Let's wait for Jess's lecture or read ahead to the wrist joint. : : The hook of the hamate provides attachment for the medial side of the transverse carpal ligament. : : T - or at least looks like it in Netter. : Agree. : : The medial epicondyle of the humerus provides a site of attachment for the common flexor tendon. : : T : Agree. : : Pronator teres has two heads of origin and, by one head, is a flexor of the elbow. : : T - by the humeral head : Agree. : : A complete lesion of the musculocutaneous nerve entirely eliminates flexion of the forearm. : : F - see previous question. Pronator teres can flex the forearm and is innervated by the median nerve. : Agree. : : A complete lesion of the musculocutaneous and radial nerves entirely eliminates flexion of the forearm. : : F - see above? : Agree. : : A complete lesion of the musculocutaneous, radial, and ulnar nerves entirely eliminates flexion of the forearm. : : F - see above? : Agree. : : A complete lesion of the musculocutaneous, radial, median, and ulnar nerves entirely eliminates flexion of the forearm. : : T - this would eliminate all the lines (branches?) of the brachial "M" descending into the forearm. : Agree. Plus the non-M radial nerve. : : A complete lesion of the radial nerve weakens flexion at the elbow. : : T - loss of brachioradialis : Agree. : : A complete lesion of the ulnar nerve is expected to cause the resting position of the wrist to be extended and radially deviated wrist. : : T - loss of flexor carpi ulnaris : Agree. And a shifting of balance toward wrist extensors and wrist abductors. Notably, extensor carpi radialis longus. : : A complete lesion of the radial nerve is expected to cause the resting position of the wrist to be adducted and flexed. : : T - loss of extensor carpi radialis? : Agree. And a shifting of balance toward ulnar deviation and wrist flexion. : : A complete lesion of the medial nerve is expected to cause the resting position of the wrist to be adducted and extended. : : There's a medial nerve? : Agree. All right. The median nerve. True. Flexor carpi radialis and the radial tendons of flexor digitorum profundus loose their contribution to balance. Adduction and extension at the wrist. : : A complete lesion of the musculocutaneous leaves the resting position of the wrist to be neutral. : : T? : Agree. There are no muscles that cross the wrist joint that are innervated by the musculocutaneous nerve. : : A complete lesion of the ulnar nerve is expected to cause the resting position radial two fingers to be hyperextended at the metacarpophalangeal joint. : : F - ulnar two fingers? : True. - Claw hand. More so for the ulnar two fingers. Why? Lumbricals plus interossei versus only interossei. : : A complete lesion of the ulnar nerve is expected to cause the resting position radial two fingers to be flexed at the interphalangeal joints. : : F - 4th and 5th digits (the ulnar two fingers) : True. Claw hand. Extension of the radial two fingers will be weakened by the loss of the interossei. The key to accepting this resides in knowing about the tethering of flexor tendons caused by hyperextension at the MP joints. I am planing an "optional" 15 min lecture devoted to grip and claw hand at the end of Jess's lecture on the joints. : : A complete lesion of the ulnar nerve is expected to cause the resting position ulnar two fingers to be hyperextended at the metacarpophalangeal joint. : : T : Agree. Same for the radial two fingers but less so. : : A complete lesion of the ulnar nerve is expected to cause the resting position ulnar two fingers to be flexed at the interphalangeal joints. : : T : Agree. : : The anterior interosseous nerve, but not the brachial artery, passes posterior to the humeral head of the pronator teres. : : T - brachial has usually already split into radial/ulnar somewhere in the cubital fossa : Agree. To be safe, this question should be reworded to read "the median nerve passes posterior to the humeral head of pronator teres and the ulnar artery passes posterior to the ulnar head of pronator teres." Thus, making the point that the ulnar head of pronator teres intervenes between the median nerve and the ulnar artery. As always, it is helpful to know the relationships of structures and they cross boundaries from one region (cubital fossa) to another region (forearm). : : The radial two heads of the flexor digitorum profundus muscle are innervated by the superficial branch of the radial nerve. : : F? - anterior interosseus branch of median nerve? It seemed like in lecture there were only two heads of this muscle (coming from ulna and coming from interosseus membrane), so I'm not sure what "radial two heads" means here. : Agree. I made this question doubly false to avoid forcing the interpretation of whether or not to equate the anterior interosseous nerve with the median nerve. Had I forced making this decision on a true/false question the question would, most likely, by neutralized on an exam. Further, to avoid your concern, I could have written "lateral two tendons." Nevertheless, I think I am safe in having heads from a common origin. Erector spinae. : : Flexion of the distal interphalangeal joints is provided for by one muscle only whereas intrinsic muscles and long extensors act together to extend the distal interphalangeal joints. : : F? - It looks like only flexor digitorum profundus flexes the DIP joints and only extensor digitorum extends them. : True. Lumbricals and interossei. Dorsal hood redux. : : The pronator quadratus receives the most distal motor innervation from the posterior interosseous nerve. : : F - I don't know what receives the most distal innervation of this nerve, but it can't be pronator quadratus. It's innervated by the anterior interosseus branch of median nerve. : Agree. The pronator quadratus receives the most distal motor innervation from the anterior interosseous nerve. "Motor" is critical to evaluating this question. : : The antebrachial fascia has medial and lateral intermuscular septae. : : F? - seems like in lab today I was dissecting through many small septae surrounding individual muscles, rather than a single medial or lateral septa on each side of the bones. : : Immediately posterior to the small gap between flexor carpi radialis and palmaris longus at the wrist is the median nerve. : Agree. Sort of. The forearm is compartmentalized. You can't define compartments by the interosseous membrane only. To be revisited. : 27. Immediately posterior to the small gap between flexor carpi radialis and palmaris longus at the wrist is the median nerve. : : F - between plantaris and flexor pollucis longus. : True. Gray's 49.13. : : At the mid-forearm level the ulnar artery and nerve are lateral to the flexor carpi ulnaris, medial to flexor digitorum superficialis, and anterior to the flexor digitorum profundus. : : T - they are medial to most of flexor digitorum superficialis, although I think it could also be argued that they are instead posterior. : Agree. No argument except for "instead." There is merit to medial/posterior. : : The pisiform bone and the tubercle of the scaphoid bone provide proximal attachments for the flexor retinaculum. : : T : Agree. : : The ulnar nerve lies lateral to the ulnar artery within Guyon's tunnel. : : F - medial : Agree. A mnemonic; the ulnar artery continues to the superficial palmar arch without crossing the ulnar nerve. The nerve has to be medial. : : : The tendon of flexor carpi radialis is at risk for compression ischemia if carpal tunnel syndrome is in effect. : : F - it's in its own little tunnel? Mechanistically though, I'm thinking that if there's inflammation/irritation of the carpal tunnel, it will tighten the anterior and posterior layers forming the tunnel for FCR, thus maybe compressing it. : Agree. Your reasoning is sound but let's not go there. My understanding of the syndrome is that FCR is not involved. Nevertheless, we are not asking you to know the specifics of clinical symptoms that can not be predicted solely by anatomical knowledge. : : Compression of the median nerve within the carpal tunnel may lead to a supinated resting position for the thumb (ape hand). : : T? If the thumb can supinate without the rest of the hand. The thumb is adducted and rotated (laterally?) and opposition is lost. : Agree. I am not sure why you have mentioned hand supination. The forearm supinates and the thumb supinates. Willful supination of the thumb is limited. Lesion the recurrent median nerve and the thumb will unwillfully supinate. : Thanks for going out on a limb (get it?) so that we could start a public dialog.

Link URL:  
Link Title:
Image URL: