Discuss the anterior compartment of the arm. Include contents, compartments, relationships, boundaries, fascial specializations, vascularization, innervation, lymphatics, muscles and movements, and compensation in the case of nerve injury.

(note: Christi's document needs to be reformatted for a more readable display on this page. Download her word doc at the bottom of the page for a more easy to read version. I may find time to reformat this myself but your previous exams are beckoning for my attention. I reformatted the "general" section. You can look at my reformatting in "raw view" or "edit" mode to see what has to be done. Do not, however, spend time reformatting this if doing so compromises your study time. lae)

Does anyone have any ideas on “compartments” or “compensation in the case of nerve injury?” I couldn’t find anything about those parts of the question…

General

• The anterior compartment of the arm is responsible for flexing the forearm
• The major things contained in it are:
  • Muscles: coracobrachialis, brachialis, and biceps brachii
    • All of these muscles are innervated by the musculocutaneous nerve (C6 & C7) from the lateral cord of the brachial plexus, and they are innervated by muscular branches of the brachial artery. The brachialis also receives a minor branch from the radial nerve.
  • Vessels:
    • Arteries: brachial artery and its branches (deep brachial artery, superior ulnar collateral, inferior ulnar collateral)
    • Veins: cephalic, basilica, brachial
  • Nerves: musculocutaneous, median nerve, ulnar nerve, medial brachial nerve, medial antebrachial nerve, intercostobrachial
  • Nodes: infraclavicular and supratrochlear
• Boudaries
  • Posterior
    • Humerus
    • Medial and Lateral Intermuscular septum extending from humerus to brachial fascia
  • Anterior
    • Brachial Fascia, tela subcutanea, dermis, epidermis
    • Superolaterally anterior---anterior portion of deltoid
  • Inferior
    • Cubital fossa
  • Superior
    • Glenohumeral joint
    • deltoid

Muscles

Coracobrachialis General O: coracoid process of scapula I: middle 1/3 of medial humerus A: adduct arm, weakly flexes arm at glenohumeral joint N: musculocutaneous V: muscular branch from brachial artery Relations Superficial/medial to humerus Deep to biceps brachii At it’s insertion at the coracoid process, it inserts deep to the tendon of the short head of biceps brachii The musculocutaneous nerve pierces through the belly of the coracobrachialis to get into the anterior portion of the arm Bicpes Brachii General O: long head---supraglenoid tubercle of scapula. The tendon courses through the intertubercular sulcus of the humerus andis wrapped in a synovial diverticulum. While coursing through the intertubercular sulcus, it is covered superficially by the transverse humeral ligament Short head----coracoid process (superficial to coracobrachialis) I: posterior lip of radial tuberosity via tendon of insertion (between radial tuberosity and radial groove of ulna) and antebrachial fascia via bicipital aponeurosis A: 1. suppination of pronated forearm As the tendon of insertion contracts, it causes the radius to rotate medially along a longitudinal axis, causing it to cross over the ulna. Once prone, the tendon is no longer in between the radial tuberosity and radial groove of ulna, but instead wraps around the neck of the radius and is separated from the bone by the bicpitoradial bursa 2. Flexion of the forearm Biceps brachii is a week flexor of the forearm and is used for extra power to supplement the brachialis. It is able to flex because of the bicipital aponeurosis’s insertion into the antebrachial fascia. Contributes to flexion when the flexed forarem is supine or semiprone, but not when it is prone N: musculocutaneous V: muscular branch of brachial artery Relationships Superficial to coracobrachialis and brachialis. Tendon of insertion passes through cubital fossa between the radial nerve and brachial artery Superficial to musculocutaneous nerve (runs between biceps brachii and brachialis

Brachialis General O: distal half of anterior humerus (inferior to instertion of deltoid) and from the intermuscular septa of the arm I: anterior surface of coranoid process of ulna and ulnaru tuberosity A: flex forarem N: musculocuteneous and small branch of radial nerve (C7) V: muscular branch from brachial artery Relations Inferior to deltoid Deep to biceps brachii Deep to musculocutaneous nerve

Innervation:

Somatic Afferent and Efferent: Muscles of anterior compartment are innervated by musculocutaneous and a branch of radial nerve Cutaneous Cutaneous innervation of anterior compartment by medial brachial cutaneous nerve (from medial cord) Sympathetic Presympathetic Originate in lateral gray column neuros of T1 to T2 Go to upper cervical and upper thoracic sympathetic ganglia Postsympathetic Go to brachial plexus via gray rami communicans of C8 and T1 spinal nerves Distributed w/ fibers of brachial plexus (in this case, musculocutaneous) to smooth muscle of vessels, sweat glands, and hair follicles Parasympathetic

Other thoughts Nerves that pass through: musculocutaneous, lateral cutaneous nerve of forearm (continuation of musculocutaneous after it gives off its muscular branches), median, ulnar, radial (medial brachial cutaneous, medial antebrachial cutaneous, intercostobrachial Reflexes Tapping the biceps tendon in the cutibal fossa elicits the “biceps reflex” testing spinal cord segments C5 and C6, and the afferent/efferent limgs of the relflex arc

Vascularization

Arterial Branches of brachial artery Brachial artery is a continuation of axillary (changes names after passing inferior boundary of teres major) Terminates in cubital fossa by giving off radial and ulnar branches Runs medially down the arm superficial to coracobrachialis then brachialis, deep to biceps brachii Branches: Profunda brachii---leaves anterior compartment and courses posteriorly radial nerve Inferior and superior unlar collateral (of elbow anastomosis) Venous Brachial Veins (vena commatantes) ---drain deep structures Cephalic and basilic---drain superficial structures

Lymph

Supratrochlear nodes----locted above medial epicondyle of humerus, medial to the basilica vein. Drain C7 and C8 dermatomes (in hand/forearm)

• • • located in anterior arm but do not drain anterior arm

deltoidopectoral

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