Overview of Upper Limb

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Remove skin and subcutaneous tissue (superficial fascia) of BOTH upper limbs, and examine the superficial veins

Find these structures:

- Basilic v.
- Cephalic v.
- Median cubital v.

1.) Beginning with the shoulder region., remove the skin and subcutaneous tissue of both upper limbs. Do NOT remove the superficial tissues distal to the wrist (radiocarpal) joint. You will observe cutaneous nerves and superficial veins (cephalic & basilic vv.) in this step; however, these can be removed in order to better visualize the muscles of the upper limb.

Note: Like most veins, the superficial vv. of the upper limb are inconstant. One may generally conceptualize two major vv.: a cephalic v. coursing along the lateral border of the upper limb, and a basilic v. coursing along the medial border of the upper limb. Veins draining the digits and hands flow into these major vv. Frequently, the median cubital v., a venous anastomosis between these vv., may be found in the vicinity of the cubital fossa, and any of these three vv. may be a common vessel for venipuncture of the upper limb. The basilic v. pierces the brachial fascia to join the brachial vv. to form the axillary v. The cephalic v. travels through the deltopectoral triangle to join the axillary v.

Photo 1. Superficial veins

2.) Observe or conceptualize (if removed in previous step) the deep (investing) fascia.

Note: The upper limb is colloquially referred to as the arm, but anatomically, the arm (or, brachium) is the region of the upper limb occupied by the humerus, and the forearm (or, antebrachium) is occupied by the radius and ulna. Therefore, the deep fascia of the arm is called brachial fascia, while the deep fascia of the forearm is the antebrachial fascia.

Photo 2. Deep (investing) fascia

Examine the deltoid muscle & neurovasculature of the shoulder

Find these structures:

- Deltoid m.
- Axillary n.
- Posterior circumflex humeral a.

3.) Locate the deltoid m.

Photo 3. Deltoid m.

4.) Detach the deltoid m. from the spine of the scapula, and reflect the deltoid laterally to see the neurovasculature of the deltoid m., the axillary n. and posterior circumflex humeral a.

Note: With the deltoid m. reflected laterally and from the posterior, one can see some of the rotator cuff mm. in association with the scapula and proximal humerus. The neurovasculature which serves the deltoid m. (axillary n. & posterior circumflex humeral a.) is transmitted through the quadrangular space (the area bounded laterally by the surgical neck of the humerus, medially by the long head of triceps brachii m., superiorly by teres minor m., and inferiorly by teres major m.).

Photo 4. Axillary n. & posterior circumflex humeral a.

Examine the muscles & neurovasculature of anterior compartment of the arm

Find these structures:

- Biceps brachii m.
- Coracobrachialis m.
- Brachialis m.
- Musculocutaneous n.
- Brachial a. and Brachial vv.

5.) Make a vertical incision through the brachial fascia of the anterior compartment sagittally, and reflect medially and laterally.

6.) Identify the muscles of the anterior compartment of the arm: biceps brachii m., coracobrachialis m., and brachialis m. If there is limited muscle mobility in this compartment, unilaterally reflect the biceps brachii m. to identify the coracobrachialis and brachialis mm.

Note: The muscles of the anterior compartment of the arm are innervated by the musculocutaneous n. and predominately supplied by the brachial a.

Photo 5. Anterior compartment of arm, superficial

Photo 6. Anterior compartment of arm, deep

7.) Identify the musculocutaneous n. It is easiest to locate proximally as it pierces the coracobrachialis m. Move (do not reflect) the muscles to locate the brachial a. & v.

Note: Brachial a. is the direct continuation of the axillary a., the transition is the inferior border of the teres major m. tendon. The brachial a. splits into two terminal branches (radial and ulnar) just distal to the elbow joint. The brachial vv. are venae comitantes (accompanying veins) of the brachial a.

Note: The deep veins of the upper limb are typically venae comitantes of their arterial counterparts. Venae comitantes are frequently paired, although they may be unpaired, and the return of blood is aided by forces from both the contraction of muscles surrounding the veins and the pulsations of the arteries that they accompany.

Photo 7. Musculocutaneous n. and brachial a. & vv.

Examine the muscles & neurovasculature of posterior compartment of the arm

Find these structures:

- Triceps brachii m.
- Radial n.
- Deep artery of arm & Deep veins of arm

8.) Identify and clean the long & lateral heads of the triceps brachii m. You will need to make a vertical incision through the brachial fascia to better view the muscle.

Note: Triceps brachii m. has 3 heads (long, lateral, & medial). The long head crosses the shoulder and elbow joints and the lateral & medial heads cross the elbow. The distal attachment for the three muscle bellies is the olecranon of the ulna. Triceps brachii m. is a powerful extensor of the elbow joint, and is innervated by the radial n. and supplied by the deep artery of arm.

Photo 8. Triceps brachii m., long & lateral heads

9.) With scissors, cut the long head of triceps brachii m., mid-belly. Locate the medial head of triceps brachii m. and the radial n. and deep artery & veins of arm.

Note: The deep artery of arm (profunda brachii a.) is a branch of the brachial a. that travels in close association with the radial n. in the radial groove of the humerus. This portion of the humerus is a common area for fracture, and can have clinical implications for the posterior compartments of the arm and forearm.

Photo 9. Triceps brachii m., medial head & neurovasculature

Examine the muscles & neurovasculature of the anterior compartment of the forearm

Find these structures:

- Anterior (flexor) compartment of forearm
  - Superficial layer
    - Pronator teres
    - Flexor carpi radialis m.
    - Palmaris longus m.
    - Flexor carpi ulnaris m.
  - Flexor digitorum superficialis m.
  - Deep layer
    - Flexor digitorum profundus m.
    - Flexor pollicis longus m.
- Radial a. & vv.
- Ulnar a. & vv.
  - Common interosseous a.
    - Anterior interosseous a.
    - Posterior interosseous a.
- Ulnar n.
- Median n.

10.) With scissors, open the antebrachial fascia, to find and identify the superficial muscles of the anterior forearm and related structures.

Note: The anterior (flexor) compartment of the forearm is organized in three layers, largely with superficial muscles acting upon proximal joints, and intermediate and deep layers acting upon progressively more distal joints.

Photo 10. Superficial forearm

11.) Locate the bifurcation of the brachial a. and its terminal branches -- the radial a. and ulnar a. -- in the vicinity of the cubital fossa.

Note: The brachial a. divides into its terminal branches (radial and ulnar aa.) in the vicinity of the cubital fossa. These arteries dive deeper within the forearm, and re-emerge in the superficial aspect of the distal forearm.

Photo 11. Brachial a. and terminal branches

12.) Using blunt dissection, locate the three layers of muscles of the anterior (flexor) compartment of the forearm.

Note: The common flexor tendon, a robust tendon originating from the medial epicondyle of the humerus, serves as a common tendon for many of the muscles of anterior (flexor) compartment of the forearm. Injury (repetitive) and/or inflammation of this area is known as medial epicondylitis (golfer’s elbow).

Note: The superficial layer of the forearm muscles consists of four muscles (including pronator teres m. and the highly variable palmaris longus m.). The superficial layer is mostly innervated by the median n. (excepting flexor carpi ulnaris m., which is innervated by the ulnar n.), and supplied by the ulnar a. The muscles of the superficial layer primarily act to flex, adduct, or abduct the wrist.

Note: The median n. is visible entering the forearm between the heads of the pronator teres m.

Photo 12. Superficial layer of anterior forearm muscles

Photo 13. Flexor digitorum superficialis m.

Note: The deep layer of the forearm muscles consists of three muscles primarily innervated by the median n. (except for the ulnar half of flexor digitorum profundus m., which is innervated by the ulnar n.) and served by the ulnar a. (either directly, or by one of its branches, the anterior interosseous a.).

Photo 14. Deep layer of anterior forearm muscles

13.) Follow the ulnar a. into the anterior (flexor) compartment, and locate the common interosseous a. deep to pronator teres m. Follow the common interosseous a. to find its bifurcation into anterior & posterior interosseous aa.

Note: The common interosseous a. branches from the ulnar a. a short distance from the origin of the ulnar a. Deep to the anterior (flexor) compartment of the forearm is the interosseous membrane of the forearm. The anterior & posterior interosseous aa. are named for their relative positions (and subsequent compartments served) to the interosseous membrane of the forearm.

Photo 15. Common interosseous a. and branches

Examine the muscles & neurovasculature of the posterior compartment of the forearm

Find these structures:

- Posterior (Extensor) Compartment of Forearm - Muscles
- Brachioradialis m.
  - Superficial layer
    - Extensor carpi radialis longus m.
    - Extensor carpi radialis brevis m.
    - Extensor digitorum m.
    - Extensor digiti minimi m.
    - Extensor carpi ulnaris m.
  - Deep layer
    - Supinator m.
- Posterior interosseous a. & vv.

14.) Locate the posterior (extensor) compartment of the forearm, and identify and examine its muscles and neurovasculature.

Note: The posterior (extensor) compartment of the forearm is conceptualized in two layers of muscles: superficial and deep.

Note: The brachioradialis m. is the most lateral (radial) muscle of the superficial posterior compartment. It shares common neurovasculature (radial n. & a.) with the superficial layer of extensor mm., however, the brachioradialis m. acts proximally upon the elbow joint rather than upon joints distal to the forearm, which is standard for the superficial layer mm.

Photo 16. Superficial layer of posterior forearm muscles

Note: Most of the muscles of the superficial layer originate via a common extensor tendon, which attaches to the lateral epicondyle of the humerus. Injury (repetitive) and/or inflammation of this area is known as lateral epicondylitis (tennis elbow).

Photo 17. Common extensor tendon

Photo 18. Deep layer of posterior forearm muscles

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