HSF/Dissection/Upper limb

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Contents 1 Notes 1.1 Muscles of upper extremity 1.2 Nerves, vessels, and their courses 1.3 Structures to identify 2 Quiz

Notes

Muscles of upper extremity

Muscle	Action	Innervation
Anterior chamber of arm
Biceps brachii	Flex at shoulder, flex at elbow, supinate at radioulnar joint	Musculocutaneous n.
Coracobrachialis	Flex at shoulder	Musculocutaneous n.
Brachialis	Flex at elbow	Musculocutaneous n.
Posterior chamber of arm
Triceps brachii	Extend at shoulder, extend at elbow	Radial n.
Anterior forearm
Pronator teres	Pronate at radioulnar joint	Median n.
Flexor carpi radialis	Flex at elbow, flex and abduct at wrist	Median n.
Palmaris longus	Flex at wrist and elbow	Median n.
Flexor carpi ulnaris	Flex and adduct at wrist, flex at elbow	Ulnar n.
Flexor digitorum superficialis	Flex at MP and PIP joints, flex at wrist and elbow	Median n.
Flexor digitorum profundus	Flex at MP, PIP, and DIP joints, flex at wrist	Median (deep) and ulnar nn.
Flexor pollicis longus	Flex thumb at MP and IP joints, flex at wrist	Median (deep) n.
Pronator quadratus	Pronate at radioulnar joints	Median (deep) n.

Nerves, vessels, and their courses

Partners	Passageway
Median n. Brachial a.	Medial intermuscular septum of arm (medial to biceps brachii, superficial to brachialis)
Radial n. Profunda brachii a.	Triangular interval
Axillary n. Posterior circumflex humeral a.	Quadrangular space
Median n.	Between ulnar and humeral heads of pronator teres

Structures to identify

Cubital fossa, lateral to medial:

• Biceps brachii tendon
• Brachial a.
• Median n.

Forearm, lateral to medial:

• Brachioradialis
• Radial a.
• Flexor carpi radialis
• Median n.
• Palmaris longus
• Flexor digitorum superficialis
• Ulnar a.
• Ulnar n.
• Flexor carpi ulnaris

Others:

• Lateral antebrachial cutaneous n. (the cutaneous branch of the musculocutaneous n.)
• Medial antebrachial cutaneous n. (the final branch off of the medial cord of the brachial plexus)
• Supinator muscle (deep to brachioradialis)
• Anterior interosseus a. (anterior branch of ulnar a., inferior to pronator teres)
• Pronator quadratus (deep to flexor digitorum profundus tendons)
• Anconeus (posterior forearm, between olecranon and lateral epicondyle of ulna)
• Profunda brachii a. (approximately one-third of the way down the humerus)
• Superior ulnar collateral a. (halfway down humerus)
• Inferior ulnar collateral a. (approximately 5cm proximal to cubital fossa)

If time permits:

• Flexor pollicis longus and brevis (lateral to brachioradialis)
• Anterior interosseus n. (branches from medial n. near pronator teres)

Quiz

1. What are the muscles of the forearm, from lateral to medial?
   • Brachioradialis
   • Radial a.
   • Flexor carpi radialis
   • Median n.
   • Palmaris longus
   • Flexor digitorum superficialis
   • Ulnar a.
   • Ulnar n.
   • Flexor carpi ulnaris
2. What are these muscles innervated by?

   All by median n. except for brachioradialis (radial n.), and flexor carpi ulnaris (ulnar n.), and the ulnar half of the flexor digitorum profundus (ulnar n.)

3. What nerve branches from the median n. at the cubital fossa?

   Anterior interosseus n.

4. What muscle lies deep to the flexor digitorum superficialis?

   Flexor digitorum profundus

5. What are the actions of the flexor digitorum muscles?

   Flex the MP and PIP joints of digits 2-5

6. What artery do the anterior and posterior interosseus arteries branch from?

   Ulnar a. (which is itself a branch of the brachial a.)

7. What ventral rami contribute to the median nerve?

   C6, C7, C8, T1

8. What nerve pierces the coracobrachialis?

   Musculocutaneous n.

9. What nerves and vessels can be seen in the quadrangular space?

   Axillary n., posterior circumflex humeral a.

10. What nerves and vessels are found between the long and lateral heads of the triceps brachii (ie, within the triangular interval)?

    Radial n., profunda brachii a. (aka, deep artery of the arm)

11. What vessels and/or nerves travel together in the medial intermuscular septum of the arm?

    Brachial a. and median n.

12. What are the branches of the brachial artery?

    Profunda brachii a., superior ulnar collateral a., and inferior ulnar collateral a.

13. Why is the ulnar nerve most susceptible to injury at the elbow?

    It passes the elbow superficially to the medial epicondyle, making it vulnerable.