axilla and brachial plexus abba

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Page 1: Axilla and brachial plexus abba
Page 2: Axilla and brachial plexus abba

AXILLA (CERVICOAXILLARY CANAL)The Axilla , or armpit, is a pyramidal-shaped space

between the upper part of the arm and the side of the chest.

It forms an important passage for nerves, blood and lymph vessels as they travel from the root of the neck to the upper limb.

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Key muscles of the Axilla Pectoralis minor: is a thin triangular

muscle that lies beneath the pectoralis major . It arises from the 3rd, 4th& 5th ribs and runs upwards and laterally to be inserted by its apex into the coracoid process of the scapula. It crosses the axillary artery and the brachial plexus of nerves. It is used when describing the axillary artery to divide it into 3 parts

Clinical Notes: Absent of Pectoralis Major. The sternocostal origin is the most commonly missing part, and this causes weakness in adduction and medial rotation of the shoulder joint.

Clavipectoral fascia is a strong sheet of connective tissue that is attached above to the clavicle. Below, it splits to enclose the pectoralis minor muscle and then continues downward as the suspensory ligament of the axilla and joins the fascial floor of the armpit.

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Axilla

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Boundaries of the AxillaThe walls, Floor and Roof of the Axilla are made up as

follows: Apex: The upper end of the axilla, is directed into

the root of the neck and is bounded in front by the clavicle, behind by the upper border of the scapula, and medially by the outer border of the first rib.

Base: It is bounded in front by the anterior axillary fold (formed by the lower border of pectoralis major muscle), behind by the posterior axillary fold (formed by the tendon of latissimus dorsi and teres major muscles), and medially by the chest wall.

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Boundaries of the AxillaAnterior wall: By the pectoralis

major, subclavius, and pectoralis minor muscles

Posterior wall: By the subscapularis, latissimus dorsi, and teres major muscles, from above down.

Medial wall: By the upper four or five ribs and their costal spaces covered by the serratus anterior muscle

Lateral wall: By coracobrachialis and biceps muscles related to the upper portion of the humerus

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Contents of the Axilla

The axilla contains: Axillary artery and its branches, which supply blood to the

upper limb; Axillary vein and its tributaries, which drain blood from

the upper limb lymph vessels and lymph nodes, which drain lymph from

the upper limb and the breast and from the skin of the trunk, down as far as the level of the umbilicus.

Lying among these structures in the axilla is an important nerve plexus, the brachial plexus, which innervates the upper limb and these are embedded in fat.

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Axillary artery

The axillary artery begins at the lateral border of the 1st rib as a continuation of the subclavian artery and ends at the lower border of the teres major muscle, where it continues as the brachial artery.

Throughout its course the artery is closely related to the cords of the brachial plexus and their branches; and enclosed with them in a connective tissue sheath called the axillary sheath, which is continuous with prevertebral fascia. The pectoralis minor muscle crosses in front of the axillary artery and divides it into three parts as follows:

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Relationship of the brachial plexus to the axillary artery

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3 parts of Axillary artery

1st part of the Axillary Artery: extends from the lateral border of the 1st rib to the upper border of the pectoralis minor

2nd part of the Axillary Artery: lies behind the pectoralis minor muscle

3rd part of the Axillary Artery: lies between the lower border of pectoralis minor muscle and lower border of teres major.

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Parts of Axillary artery

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Branches of the axillary arterythe branches of the axillary artery supply the thoracic

wall and the shoulder region. They are:The 1st part of the artery gives off one branch (the

highest thoracic artery),The 2nd part give off two branches (the

thoracoacromial artery and the lateral thoracic artery),

And the 3rd part gives off three branches (the subscapular artery, the anterior circumflex humeral artery, and the posterior circumflex humeral artery)

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Branches of axillary artery 1st part (1 br.), 2nd part (2 brs.) & 3rd part

(3 brs.) 1 superior thoracic a. ;(supreme

thoracic a.; highest thoracic a.) 2 thoracoacromial a. 3 lateral thoracic a. 4 subscapular a. 5 anterior humeral circumflex a. 6 posterior humeral circumflex a. 4a thoracodorsal branch of

subscapular 4b scapular circumflex branch of

subscapular 8 brachial artery (continuation of the

axillary) below lower border of teres major (tm)

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Branches of axillary artery cont.The highest thoracic artery is small and runs along

the upper border of the pectoralis minor. The thoracoacromial (acromio-thoracic) artery

immediately divides into terminal branches (CHAP; Clavicular, Humeral (Deltoid), Acromial and Pectoral).

The lateral thoracic artery runs along the lower border of the pectoral minor.

The subscapular artery runs along the lower border of the subscapularis muscle.

The anterior and posterior circumflex humeral arteries wind around the front and the back of the surgical neck of the humerus respectively.

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Axillary artery and vena commitantes of brachial artery

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Axillary vein

The axillary vein is formed at the lower border of the teres major muscle by the union of the venae comitantes of the brachial artery and the basilic vein. It runs upward on the medial side of the axillary artery and ends at the lateral border of the first rib by becoming the subclavian vein.

The vein receives the cephalic vein and tributaries, which correspond to the branches of the axillary artery.

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Clinical notes

1. BRACHIAL NERVE BLOCKBecause the axillary sheath encloses the axillary vessels and thebrachial plexus, a brachial plexus nerve block can easily be obtained.The distal part of the sheath is closed with finger pressure, and asyringe needle is inserted into the proximal part of the sheath. Theanesthetic solution is then injected into the sheath. And the solution ismassaged along the sheath to produce the nerve block. The positionof the sheath can be verified by feeling the pulsations of the third part ofthe axillary artery.2. SPONTANEOUS THROMBOSIS OF THE AXILLARY VEINSpontaneous thrombosis of the axillary vein occasionally occurs afterexcessive and unaccustomed movement of the arm at the shoulderjoint.

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LYMPH NODES OF THE AXILLA

The axillary lymph nodes drain lymph vessels from the lateral quadrants of the breast, the superficial lymph vessels from the thoracoabdominal walls above the levels of the umbilicus, and the vessels from the upper limb. The lymph nodes are arranged in six groups.

Anterior (pectoral) group: Lying along the lower border of the pectoralis minor behind the pectoralis major, these nodes receive lymph vessels from the lateral quadrants of the breast and superficial vessels from the anterolateral abdominal wall above the level of the umbilicus.

Posterior (subscapular) group: Lying in front of the suscapularis muscle, these nodes receive superficial lymph vessels from the back, down as far as the level of the iliac crests.

Lateral group: lying along the medial side of the axillary vein, these nodes receive most of the lymph vessels of the upper limb (except those superficial vessels draining the lateral side.

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LYMPH NODES OF THE AXILLAcontdCentral group: lying in the center of the axilla in the axillary fat,

these nodes receive lymph from the above three groups. Infraclavicular (deltopectoral) group: these nodes are not strictly

axillary nodes because they are located outside the axilla. They lie in the groove between the deltoid and pectoralis major muscles and receive superficial lymph vessels from the lateral side of the hand, forearm and arm.

Apical group: lying at the apex of the axilla at the lateral border of the first rib, these nodes receive the efferent lymph vessels from all the other axillary nodes.

The apical nodes drain into the subclavian lymph trunk. On the left side, this trunk drains into the thoracic duct; on the right side, it drains into the right lymph trunk, the lymph trunks may drain directly into one of the veins at the root of the neck.

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BRACHIAL PLEXUSThe nerves entering the upper limb provide the following important functions:

Sensory innervation to the skin and deep structures, such as the joints,

motor innervation to the muscles; influence over the diameters of the blood vessels by

the sympathetic vasomotor nerves; and sympathetic secretomotor supply to the sweat gland.

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FORMATION OF BRACHIAL PLEXUS At the root of the neck, the nerves that are about to

enter the upper limb come together to form a complicated plexus called the brachial plexus. This allows the nerve fibres derived from different segments of the spinal cord to be arranged and distributed efficiently in the different nerve trunks to the various parts of the upper triangle of the neck by the union of the anterior rami of the 5th, 6th, 7th, and 8th cervical and the first thoracic spinal nerves (C5, C6, C7, C8, T1).

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Nura onyango

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Formation Cont. The plexus can be divided into roots, trunks,

divisions and cords. The roots of C5 and 6 unite to form the upper trunk, the root of C7 continues as the middle trunk, and the root of C8 and T1 unite to form the lower trunk.

Each trunk then divides into anterior and posterior divisions. The anterior divisions of the upper and middle trunks unite to form the lateral cord, the anterior division of the lower trunk continues as the medial cord, and the posterior divisions of all three trunks join to form the posterior cord.

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Location of parts of the brachial plexus

Roots: Between Scalene MusclesTrunks: Posterior Triangle of the neckDivisions: Behind the ClavicleCords: In the Axilla

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Location of parts of the brachial plexus cont.

The roots, trunks and divisions of the brachial plexus reside in the lower part of the posterior triangle of the neck.

The cords are arranged around the axillary artery in the axilla.

Here, the brachial plexus and the axillary artery and vein are enclosed by a sheath of fascia called the axillary sheath.

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Brachial plexus

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Naming the cords

All the three cords of the brachial plexus are related to the second part of the axillary artery and thus named accordingly.

The medial cord crosses behind the artery to reach the medial side of second part of the artery.

The posterior cord lies behind the second part of the artery, and

the lateral cord lies on the lateral side of second part of the artery.

Most branches of the cords that form the main nerve trunks of the upper limb continue this relationship to the artery in its third part. The branches of the different parts of the brachial plexus are as follows:

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Branches of the different parts

Roots; Dorsal scapular, long thoracic nerve Upper trunk; nerve to subclavius, suprascapular nerve Lateral cord; lateral pectoral nerve, Musculocutaneous

nerve and Lateral root of median nerve Medial cord; Medial pectoral nerve, Medial cutaneous

of arm and Medial cutaneous nerve of forarm, Ulnar nerve, Medial root of median nerve

Posterior cord; Upper and lower subscapular nerve, Thoracodorsal nerve, Axillary nerve and Radial nerve

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The various nerves

Nerve to the subclavius which supplies the subclavius muscle may give a contribution to the phrenic nerve; this branch, when present, is important clinically because it is reffered to as the accessory phrenic nerve.

The long nerve arises from the roots of the brachial plexus in

the neck and enters the axilla by passing down over the lateral border of the first rib behind the axillary vessels and brachial plexus. It descends over the lateral surface of the serratus anterior muscles, which it supplies.

The lateral pectoral nerve arises from the lateral cord of the brachial plexus and supplies the pectoralis major muscle

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The various nerves cont.

The musculocutaneous nerve arises from the lateral cord of the brachial plexus, supplies the coracobrachialis muscle, and leaves the axilla by piercing that muscle. Supplies BBC= Biceps brachii, Brachialis and Coracobrachialis

The lateral root of the median nerve is the direct continuation of the lateral cord of the brachial plexus. It is joined by the medial root to form the median nerve trunk, and this passes downward on the lateral side of the axillary artery. The median nerve gives off no branches in the axilla.

The medial pectoral nerve arises from the medial cord of the brachial plexus, pierces and supplies the pectoralis minor muscle, and supplies the pectoralis major muscle.

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The various nerves cont. The medial cutaneous nerve of the arm arises from the medial cord

of the brachial plexus and is joined by the intercostobrachial nerve (lateral cutaneous branch of the 2nd intercostal nerve) it supplies the skin on the medial side of the arm.

The medial cutaneous nerve of the forearm arises from the medial

cord of the brachial plexus and descends in front of the axillary artery.

The ulnar nerve arises from the medial cord of the brachial plexus

and descends in the interval between the axillary artery and vein. The ulnar nerve gives off no branches in the axilla.

The medial root of the median nerve arises from the medial cord of the brachial plexus and crosses in front of the third part of the axillary artery to join the lateral root of the median nerve.

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The various nerves cont.The upper and lower subscapular nerves arise from

the posterior cord of the brachial plexus and supply the upper and lower parts of the subscapularis muscle. In addition the lower subscapular nerve supplies the teres major muscle.

The thoracodorsal nerve arises from the posterior

cord of the brachial plexus and runs downward to supply the latissimus muscle.

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The various nerves cont. The axillary nerve is one of the terminal branches of the

posterior cord of the brachial plexus turns backward and passes through the quadrangular space, having given off a branch to the shoulder joint and divides into anterior and posterior branches. Supplies Deltoid and Teres minor

The radial nerve is the largest branch of the brachial plexus and lies behind the axillary artery. It gives off branches to the heads of the triceps muscle and the posterior cutaneous nerve of the arm. The latter branch is distributed to the skin on the middle of the back of the arm.

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Clinical Applications: Lesions of the brachial plexus:

Upper plexus paralysis / Erb’s Duchene paralysis involving C5&C6 producing waiter’s tip

Lower trunk lesions/ Klumpke’s paralysis, Usually T1 is torn, clawed hand

Long thoracic nerve producing Winged scapula Crutches affecting the axillary nerve. Axillary nerve leads

to impairment of abduction of upper limb Radial nerve leads to wrist drop Median nerve leads to the hand becoming flattened and

‘apelike’. Ulnar nerve leads to failure to grip and holding a piece

of paper between digits- Allen’s test

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