Acureflex Points Formed By The Brachial Plexus

The brachial plexus enters the upper limb to provide both sensory and motor functions, which include the following:

• Sensory innervation to the skin and joints

• Motor innervation to the muscles

• Influence over the diameters of the blood vessels via the sympathetic vasomotor nerves

• Sympathetic secretomotor supply to the sweat glands

The brachial plexus arises just lateral to the scalenus anterior muscle. The ventral rami of C5, C6, C7, and C8 and the greater part of T1, in addition to a communicating loop from C4 to C5 and one from T2 (sensory) to T1, form the five roots, three trunks, six divisions (three anterior and three posterior), three cords, and five terminal branches (see Fig. 8-7).

The anterior divisions form the lateral and medial cords, which give rise to their peripheral nerves innervating anterior or flexor muscles of the upper extremity. The posterior divisions form a posterior cord, which gives rise to its peripheral nerves innervating the posterior or extensor muscles of the upper extremity. With this 5-3-6-3-5 scheme, it is easier to understand the logical configuration of the brachial plexus.

The five roots form the three trunks: superior, middle, and inferior. The superior trunk consists of jointed ventral rami of C5 and C6 fibers. The middle trunk contains C7 fibers. The inferior trunk contains joint C8 and T1 fibers. Each of the three trunks splits into two branches: the anterior and posterior divisions for flexor (preaxial) and extensor (postaxial) muscles, respectively.

The three cords—the lateral, medial, and posterior—are formed by the six divisions. The anterior divisions from the superior and middle trunks, composed of C5, C6, and C7 fibers, unite to form the lateral cord. The anterior division from the inferior trunk, composed of C8 and T1 fibers, forms the medial cord. The posterior divisions from all three trunks, composed of C5 through C8 fibers, unite to form the posterior cord.

The cords then divide and reunite into branches that become peripheral nerves. The posterior cord branches into the axillary and radial nerves. The medial cord, after receiving a branch from the lateral cord, terminates as the ulnar nerve. One branch of the lateral cord becomes the musculocutaneous nerve; the other branch unites with one from the medial cord to form the median nerve.

The brachial plexus extends from the neck into the axilla, situated partly in the neck and partly in the axilla. The supraclavicular part (rami and trunks with their branches) is in the posterior triangle of the neck, and its infraclavicular part (cords and their branches) is in the axilla (Fig. 8-15). Peripheral nerves innervating muscles of the shoulder and a few muscles of the upper arm exit directly from various components of the plexus.

Brachial plexus, infraclavicular part

Medial cord Posterior -i cord

Lateral cord

Lateral root Medial root Median nerve Axillary nerve Superior lateral cutaneous nerve of arm Musculocutaneous nerve Radial nerve

Posterior cutaneous nerve of arm Inferior lateral cutaneous nerve of arm

Lateral cutaneous nerve of forearm

Superficial branch Deep branch

Posterior cutaneous nerve of forearm

Communicating branch with ulnar nerve

Common palmar digital nerves

Brachial plexus, supraclavicular part

Proper palmar digital nerves

Posterior cutaneous nerve of forearm

Communicating branch with ulnar nerve

Common palmar digital nerves

Proper palmar digital nerves

Axillary artery

Medial cutaneous nerve of arm

Medial cutaneous nerve of forearm

Ulnar nerve

Anterior interosseous nerve

Dorsal branch (ulnar nerve) Palmar branch (ulnar nerve)

Figure 8-15 The brachial plexus.

Axillary artery

Medial cutaneous nerve of arm

Medial cutaneous nerve of forearm

Ulnar nerve

Anterior interosseous nerve

Dorsal branch (ulnar nerve) Palmar branch (ulnar nerve)

Deep branch (ulnar nerve) Superficial branch (ulnar nerve) Common palmar digital nerves Proper palmar digital nerves

Figure 8-15 The brachial plexus.

A general survey of upper limb anatomy is necessary to better understand the innervation and configuration of the brachial plexus. The upper limb is the organ of manual activity. It consists of two parts: the shoulder (junction of the arm and the trunk) and the free arm. The free arm includes four parts: the arm (brachium, between the shoulder and the elbow), the forearm (ante-brachium, between the elbow and the wrist), the wrist (carpus), and the hand (manus). The bones of the upper limb are the clavicle (collar bone) and the scapula (shoulder blade) in the shoulder; the humerus in the arm; the radius and ulna in the forearm; the eight carpal bones in the wrist; the five metacarpal bones in the hand; and the 14 phalanges in the digits (fingers) of one hand. More than 50 big and small muscles are attached to the bones of the upper limb.

The shoulder girdle and its muscles, such as the pectoralis, rhomboid, supraspinatus, and infraspi-natus muscles, in the anterior and posterior walls of the thorax are considered as belonging to the upper limb. With the exception of a small area of skin on the shoulder, the brachial plexus supplies the innervation to the skin of all those regions and all of the muscles of the upper limb.

The anterior divisions innervate two pectoral muscles in the anterior thoracic region, muscles of the anterior compartment in the brachium, muscles in the medial compartment of the antebrachium, and intrinsic muscles on the palms of the hands. The posterior divisions innervate the levator scapulae, the rhomboid major and minor, the supraspina-tus and infraspinatus in the shoulder and posterior thoracic regions, muscles in the posterior compartment of the brachium, and muscles in the lateral compartment of the antebrachium.

The cutaneous branches from the plexus have similar configuration. The cutaneous nerves from the anterior division include the medial brachial cutaneous, the medial antebrachial cutaneous and the lateral antebrachial cutaneous nerves. The posterior

Figure 8-16 The flexor and extensor compartments of the upper arm.

divisions give off branches of the posterior brachial cutaneous, the posterior antebrachial cutaneous, and the superficial radial nerve. All of the ARPs attributed to the brachial plexus are formed along these nerves, and so the points can be named according to nerves innervating the points.

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