Bio 502, Fall 2016, Lecture #11: Forearm

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ChathamBio502
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239741
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Bio 502, Fall 2016, Lecture #11: Forearm
Updated:
2016-10-19 14:11:39
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Forearm
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anatomy of the forearm
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  1. Pronation:
    A) Describe the path of the ulna during pronation
    B) list the muscles acting on the ulna during pronation and their specific functions
    • A) The ulna is mainly stable during pronation (the radius rotates about the ulna).
    • B) Anconeus abducts the ulna which maintains the center of the palm over approximately the same place as the hand turns over.
  2. List all of the motions produced by muscles in the forearm for which C8 provides primary spinal contribution.
    • 1) flex all 5 digits at the MCP joints
    • 2) flex all 5 digits at the PIP joints
    • 3) flex the 4 medial digits at the DIP joints
    • 4) palmarflex the hand at the wrist
    • 5) flex the 1st carpometacarpal joint
    • 6) pronate the forearm & hand
    • 7) abduct the ulna
    • 8) adduct the hand at the wrist
    • 9) (weakly) flex the forearm at the elbow
    • 10) resist shearing forces during gripping
  3. Describe the insertion of flexor carpi ulnaris.
    Flexor carpi ulnaris inserts directly onto the pisiform bone. It indirectly inserts onto the hamate via the pisohamate ligament and onto the base of the 5th MC via the pisometacarpal ligament.
  4. Where is the approximate location of the division of the brachial artery into the two primary arteries of the forearm and what are those two primary arteries?
    The brachial artery divides at approximately the radial head/apex of the cubital fossa into the radial and ulnar arteries.
  5. If a patient presented with lesions on spinal levels C6 and C7 rendering them non-functional, would the patient still be able to abduct the hand at the wrist using the extrinsic muscles of the forearm? If yes, list the muscle(s) that would enable this motion and the associated spinal levels of the muscle(s).
    Yes, via extensor carpi radialis brevis (C7, C8) & abductor pollicis longus (C7, C8)
  6. Why can palmaris longus help to resist shearing forces?
    Because it inserts into the palmar aponeurosis, which inserts directly into the skin of the palm and into the digits. The aponeurosis reinforces the soft tissues of the palm. When palmaris longus contracts, it pulls on the palmar aponeurosis, which pulls the skin and other soft tissue taut, thereby increasing their overall stability. Specifically, it works with the palmar aponrueosis to resist distally directed horizontal shearing forces (decreasing the likelihood that the skin of your hand will be degloved)
  7. List all of the muscles in the forearm that contribute to adduction of the hand at the wrist.
    • 1) flexor carpi ulnaris
    • 2) extensor carpi ulnaris
  8. Trace the motor innervation of extensor pollicis brevis back through the spinal levels specific to that muscle and on to the spinal cord (landmarks are not necessary).
    Extensor pollicis brevis / posterior interosseous nerve/deep radial nerve / radial nerve / posterior cord / posterior divisions of the inferior and middle trunks / anterior rami of C7&C8 / spinal nerve / anterior root
  9. Which manual digits are capable of independent flexion at their most distal interphalangeal  joint and why?
    the 1st and potentially the 2nd manual digits are capable of independent flexion at their most distal interphalangeal joints. Independent flexion in the first is achieved through recruitment of the flexor pollicis longus muscle, which is an independent muscle inserting into the pollical distal phalanx. If independent flexion occurs in the 2nd digit, it is achieved through recruitment of the flexor digitorum profundus muscle, which sends an independent muscle slip to the 2nd digit contrary to the condition in the 3rd-5th digits.
  10. True or false (if false, provide the correct information): biceps brachii assists pronator quadratus and pronator teres to pronate the forearm against resistance or during rapid movement.
    FALSE. biceps brachii assists supinator to supinate the forearm against resistance or during rapid movement.
  11. True or false (if false, provide the correct information): some of the muscles that control the movement of the thumb are located in the anterior forearm but not the posterior forearm.
    FALSE: three of the muscles operating on the thumb are located in the posterior forearm: abductor pollicis longus, extensor pollicis brevis and extensor pollicis longus
  12. True or false (if false, provide the correct information): abductor pollicis longus abducts the hand at the wrist, but does not abduct the thumb.
    FALSE. Abductor pollicis longus abducts both the hand at the wrist and the thumb at the carpometacarpal joint. When abducting the thumb, it is acting with abductor pollicis brevis. When abducting the hand at the wrist it is functioning with flexor carpi radialis and extensor carpi radialis brevis  longus.
  13. List the muscles of the forearm that originate from the medial humeral epicondyle. BE SPECIFIC.
    • 1) humeral head of flexor carpi ulnaris
    • 2) palmaris longus
    • 3) flexor carpi radialis
    • 4) humeral head of pronator teres
    • 5) humeral-ulnar head of flexor digitorum superficialis
  14. list all of the carpal bones that serve as insertion locations for the muscles of the forearm.
    • 1) pisiform
    • 2) hamate
  15. If lesions at the anterior rami of C6 - C8 rendered these fibers non functional, would the patient still be able to palmarflex the hand at the wrist? If yes, provide the remaining functional muscles and their spinal levels.
    • Yes, via:
    • 1) flexor carpi ulnaris (C7, C8, T1)
    • 2) flexor digitorum superficialis (C8, T1)
    • 3) flexor digitorum profundus (C8, T1)
  16. For the following question:
    Pick A if 1 is true
    Pick B if 1&2 are true
    Pick C if 1-3 are true
    Pick D if all are true
    Pick E if none are true

    1) two of the muscles in the posterior compartment of the forearm are able to flex the forearm at the elbow
    2) extensor carpi radialis longus and brevis have the same spinal levels
    3) extensor carpi radialis longus and brevis originate from the lateral supraepicondylar ridge
    4) the tendons of extensor digitorum profundus slip through the tendons of extensor digitorum superficialis to insert onto the distal phalanges.
    E
  17. For the following question:
    Pick A if 1 is true
    Pick B if 1&2 are true
    Pick C if 1-3 are true
    Pick D if all are true
    Pick E if none are true

    1) The radial tuberosity rotates into the ulnar notch during pronation
    2) The tendon of brachioradialis pushes the anterior fat pads into the radial and coronoid fossae during extension of the forearm
    3) The trochlear notch is formed by the trochlea and the olecranon process
    4) the anular ligament is the inferior expansion of the synovial membrane of the elbow joint
    E
  18. For the following question:
    Pick A if 1 is true
    Pick B if 1&2 are true
    Pick C if 1-3 are true
    Pick D if all are true
    Pick E if none are true

    1) The radial nerve carries fibers from C5-T1
    2) none of the muscles in the posterior compartment of the forearm receive fibers from spinal level T1
    3) only one muscle in the posterior compartment of the forearm is innervated by the deep radial nerve
    4) only one muscle in the posterior compartment of the forearm receives primary contribution from C5
    C
  19. Trace the primary blood supply/supplies of infraspanatus back to the arch of the aorta on the left side of the body, including all of the part of the relevant arteries and all relevant landmarks.
    • Primary blood supply: supraspinatus and circumflex scapular arteries.
    • Derivation of supscapular:
    • Arch of the aorta / 1st part of subclavian: from the arch to the medial border of the anterior scalene muscle / thyrocervical trunk / suprascapular artery, which travels over the suprascapular foramen, then wraps around the lateral margin of the scapular spine to enter the infraspinous fossa.


    • derivation of circumflex scapular:
    • Arch of the aorta / 1st part of subclavian: from the arch to the medial border of the anterior scalene muscle / 2nd part of subclavian: posterior to the anterior scalene muscle / 3rd part of subclavian: from 2nd part over to lateral margin of the 1st rib / 1st part of axillary artery: lateral margin of the 1st rib to superior margin of pec minor / 2nd part of axillary: posterior to pec minor / 3rd part of axillary artery: inferior margin of pec minor to inferior margin of teres major / Subscapular is the first artery off of the 3rd part of axillary / circumflex scapular artery passes into the scapular region by traveling through the triangular space.
  20. The radius and ulna lie parallel to each other in anatomical position or when the forearm is supinated?
    At both times because in anatomical position the forearm and hand are supinated.
  21. List all of the muscles in the upper limb that can slowly supinate the forearm
    supinator
  22. True or false (if false, provide the correct information): only nerves carrying fibers from the anterior divisions of the brachial plexus pass through the cubital fossa.
    TRUE (median nerve)
  23. True or false (if false, provide the correct information): even though the branch of the radial nerve innervating anconeus divides from the nerve as it passes between the heads of supinator, it is a branch of the radial nerve proper rather than deep radial.
    FALSE. The branch of radial that innervates anconeus travels from the medial head of triceps prior to the division of radial into deep and superficial and therefore before deep radial passes between the heads of supinator.

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