Upper Limb, part IShoulder, Arm, and Axilla.

Objectives:1. Bones and joints of the shoulder

2. Organization of the shoulder’s muscles

3. Axilla - borders and contents

4. Organization of the brachial plexus

Posterior viewAnterior view

Which joint serves as the only bony attachment of the upper limb to the axial skeleton?

Which of these bones is commonly fractured?

Sternal clavicular joint

clavicle

ORGANIZATION OF THE SHOULDER: MUSCLES AND INNERVATION

}rotator cuff

* Muscles (MM) ATTACH HUMERUS TO AXIAL SKELETON:

1. Latissimus Dorsi ( thoracodorsal n. C6-C8 )

2. Pectoralis Major ( lateral pectoral n. C5-C7, medial pectoral n. C8-Th1 )

- attaches to humerus* MM ATTACH HUMERUS TO THE SCAPULA

1. Supraspinatus, Infraspinatus ( suprascapular n. C5-C6 )

2. Subscapularis ( upper C5 and lower C6 subscapular nn. )

3. Teres Minor ( axillary n. C5-C6 )

4. Teres Major ( lower subscapular n. C6 )

5. Deltoid ( axillary n. C5-C6 )

* MM ATTACH SCAPULA TO AXIAL SKELETON

1. Trapezius ( spinal accesory n. XI )

2. Levator Scapulae, Rhomboids ( dorsal scapular n. C5 )

3. Serratus Anterior ( long thoracic n. C5-C7 )

4. Pectoralis Minor ( medial pectoral n. C8-Th1 )

Supraspinatus .: Assists the deltoid in the initial abduction

Infraspinatus .: Powerful lateral rotator of humerus

Teres minor .: Helps rotate the arm laterally and assists in adduction (like infraspinatus). HOWEVER, it is innervated by the axillary nerve, while the infraspinatus is innervated by the suprascapular nerve

Subscapularis .: It is the primary medial rotator (also adducts it) .: Innervated by the subscapular nerve

The The deltopectoral deltopectoral triangle is also triangle is also known as the known as the “clavicopector“clavicopectoral triangle”. al triangle”. These two These two names tells me names tells me the exact the exact borders. borders.

What’s in the What’s in the triangle? triangle?

The cephalic The cephalic veinvein

Which structures lie in the deltopectoral triangle?

Cephalic vein

The rotator cuff muscles work as a group in holding the head of the humerus in the glenoid cavity. They give protection and stability to the shoulder joint.

Rotator cuff

S I

T

Ssubscapularis

Rotator cuff is formed by the tendons of: Supraspinatus , Infraspinatus, Teres minor and Subscapularis fuses with the joint capsule.

What is the tendonitis of the rotator cuff? inflammation

Axilla (the armpit)

1. Apex – cervicoaxillary canal, the passageway between the neck and the axilla. Lies between the 1st rib, clavicle and upper border of the scapula.

2. Base - formed by the skin, subcutaneous tissue and axillary fascia

3. Four walls: * anterior wall - pectoralis major and minor mm, pectoral and clavicopectoral

fascia.Anterior axillary fold -> pectoralis major!

* posterior wall - scapula , subscapularis m., latissimus dorsi m., teres major m.Posterior axillary fold -> latissimus dorsi and teres major!

* medial wall - thoracic wall and serratus anterior m.

* lateral wall - intertubercular groove of the humerus.Fun note: Axillary fossa = armpit

What passes through the cervico-axillary cannel? .: Arteries, veins, lymphatics and nerves to and from the arm

What mainly forms the posterior wall? .: Scapula

Contents of the axilla:

• axillary artery and its branches

• axillary vein and its tributaries

• brachial plexus

• axillary lymph vessels and lymph nodes

• 3 muscles: long/short head of biceps brachii m. and coracobrachialis m.

The axillary artery and vein, and the cords of brachial plexus(neurovascular bundle) are enveloped in the thin fascial sheath - axillary sheath.

AXILLARY ARTERY

CORDS

ROOTS AND TRUNKS

NEUROVASCULAR BUNDLE

AXILLA

CLAVICLE

Axillary artery – three parts

First part - one branch – superior thoracic a.

Second part - two branches – thoracoacromial a.

– lateral thoracic a.

Third part - three branches – subscapular a.

– anterior circumflex humeral a.

– posterior circumflex humeral a.Screw the lawyer, save the patient

Superior thoracicThoracodorsalLateral thoracicSubscapularAnterior circumflex humeralPosterior circumflex humeral

The thoracoacromial artery will further branch off in 4 directions, named after parts of the body.

Mnemonic: Cadavers Are Dead People

ClavicularAcromialDeltoidPectoral

superior thoracic a.(1st part)

thoracoacromial a.(2nd part)

lateral thoracic a.(2nd part)

anterior circumflexhumeral a. (3rd part)

subscapular a.(3rd part)

thoracodorsal a.

circumflex scapular a.

posterior circumflexhumeral a. (3rd part)

Arterial anastomoses around the scapula

circumflex scapular a.

subscapular a.

axillary a.

thyrocervical trunk

deep branch of transverse cervical a.*(dorsal scapular)

anterior circumflex humeral a.

posterior circumflex humeral a.

profunda brachii a.

Scapular loop:SuprascapularDorsal scapularSubscapular

Humeral loop:anterior circumflex humeral posterior circumflex humeralprofunda brachii

.: Thoracoacromial artery-Cadavers are dead people

-1. clavicular-2. acromial-3. deltoid-4. pectoral

Arterial anastomoses form loops

Think about where the loops are located. That’s where they get the name. The anterior circumflex humeral, posterior circumflex humeral and profunda brachii are all wrapping around in the humerus

The same goes for the scapular loop, which contains the suprascapular, dorsal scapular and subscapular ateries

Axillary lymph nodes

Five principal groups:

1. Pectoral( anterior) nodes receive lymph mainly from anterior thoracic wall and the breast and abdominal wall.

2. Subscapular (posterior) nodes receives lymph from posterior thoracic wall and scapular region.

3. Humeral (lateral) nodesreceive lymph from upper limb.

4. Central nodes (base of axilla)receive lymph from anterior, posterior and lateral nodes.Drain into apical nodes.

5. Apical nodes (apex of axilla)Receive lymph from all the other nodes. Drain into the subclavian trunks.

PLAN OF BRACHIAL PLEXUS = Ventral Rami C5 to T1 ROOTS

(5)

TRUNKS

(3)

DIVISIONS

(3/3)CORDS

(3)TERMINALS

(5)

MEDIAN

ULNAR

MUSCULOCUTANEOUS

RADIAL

AXILLARY

C5

C6

C7

C8

T1

SUPERIOR

MIDDLE

INFERIOR

LATERAL

POSTERIOR

MEDIAL

DIVISIONS = ANTERIOR AND POSTERIOR

Which spinal nerves form the brachial plexus? C5, C6, C7 C8 and T1

A

P

A

Brachial plexus is formed by the union of the anterior (ventral) primary rami of C5 – T1 nerves that constitute roots of brachial plexus.

The roots of brachial plexus unite to form three trunks:* superior trunk (C5-C6)* middle trunk (C7)* inferior trunk (C8-T1)

Each trunk divides into anterior and posterior divisions of brachial plexus.

The divisions of the trunks form three cords of brachial plexus:* posterior cord - posterior divisions of all three trunks* lateral cord – anterior divisions of superior and middle trunk* medial cord – anterior division of the inferior trunk

The cords of brachial plexus give rise to most of the named peripheral nerves (branches) that result from the plexus formation.

5

6

7

8

1

Axillary nerve

Radial nerve

Ulnar nerve

Musculocutaneous nerve

Median nervePosterior cord

Medial cord

Lateral cord

Posterior divisions

Anterior divisions

Basic Anatomy of the Brachial Plexus

Ventral ramior

rootsTrunk

BRACHIAL PLEXUS

Terminal Branches:

Motor Distribution to Arm, Forearm and Hand

Roots, Trunks and Cords:

Motor Distribution to Anterior and Posterior Shoulder

CORDS OF BRACHAL PLEXUS - TERMINAL BRANCHES

I. LATERAL CORD:

1. musculocutaneous n.(C5-C7):

anterior group of arm (muscles of anterior arm are innervated; biceps, brachialis and coracobrachialis)

2. lateral root of median n.(C6-C7) :

anterior group of forearm (except flexor carpi ulnaris, medial half of flexor digitorum profundum)

thenar muscles and first two lumbricals

Musculocutaneous nerve (C5,6,7)

Coracobrachialis muscle

Ulnar nerve

Lateral cord of brachial

plexus

Lateral cutaneous nerve of forearm

Brachialis muscle

Biceps brachii muscleCutaneous innervation

( skin of lateral forearm)

Note the name: musculocutaneous

It innervates the muscles in the arm and the cutaneous layer (skin) of the forearm

What cord does this nerve spring from? The lateral cord.

This is a pretty good way to remember what part of the forearm the musculocutaneous nerve innervates.

Lateral anterior

CORDS OF BRACHAL PLEXUS - TERMINAL BRANCHES

II. MEDIAL CORD:

1. medial root of median n. (C8-T1):

anterior group of forearm (except flexor carpi ulnaris, medial half of flexor digitorum profundum)

thenar muscles and first two lumbricals

2. ulnar n. (C8-T1):

flexor carpi ulnaris

medial half of flexor digitorum profundum

all the small muscles of the hand (except thenar and two first lumbricals)

What did the lateral root of the median nerve innervate? .: thenar muscles, first two lumbricals, and anterior group of forearm except for flexor carpi ulnaris and medial half of flexor digitorum profundum

Does the medial root of the median nerve innervate these exceptions? .: No, in fact it does the same thing as the lateral root (these cords join together to form the median nerve

So what does innervate the flexor carpi ulnaris and the medial half of flexor digitorum profundum? .: ulnar nerve

Anything else? .: All the small muscles of the hand except for the thenar and the first two lumbricals, which is what the median nerve takes care of.

Common & proper digital

nerves

Palmar branch of

median nerve

Median nerve (C5,6,7,8,T1)

Medial cord of brachial plexus

Cutaneous innervation

Lateral cord of brachial plexus

Muscles of hand (thenar group and two first lumbricals)

Flexors of forearm except fl.carp.ulnaris and medial flexor dig. profundus

Muscles of forearm

Note that the median nerve only cutaneously innervates the anterior part of the hand, and the back of the fingertips, not the rest of the back of the hand.

The pimp hand is felt with the radial nerve and the ulnar, I believe.

Flexor carpi ulnaris muscle

Dorsal branch of ulnar nerve

Deep & superficial branch of ulnar nerve

Proper palmar digital nerves

Note: Only muscles innervated by ulnar nerve shown

Medial epicondyle

Cutaneous innervation

Flexor dig. profundus (medial part)

Muscles of the hand

(excluding thenar and

two lumbrical muscles)

Ulnar nerve (C7,8,T1)

CORDS OF BRACHAL PLEXUS - TERMINAL BRANCHES

III. POSTERIOR CORD:

1. axillary n. (C5-C6):

deltoid,

teres minor

2. radial n. (C5-T1):

posterior group of arm and forearm

In what situations the axillary nerve may be damaged (injured)?

Fracture of the surgical neck

Dislocation of the glenohumeral joint

Compression from the incorrect use of crutches

Posterior interosseous nerve (continuation of deep branch of Radial nerve)

Dorsal digital nerves

Superficial branch of radial nerve

a

Superficial and deep branch of radial

nerve

Radial nerve(C5,6,7,8)

C5

C6

C7

C8

T1

ROOTS

BRACHIAL PLEXUS – branches of ROOTS, TRUNKS AND CORDS

DORSAL SCAPULAR C5RHOMBOID MM AND LEVATOR SCAPULE

SUPRASCAPULAR C5,6SUPRASPINATUS MINFRASPINATUS M

LONG THORACIC C5-C7SERRATUS ANTERIOR M

SUBSCAPULAR NN C5,6 SUBSCAPULARIS MTERES MAJOR M

LATERAL PECTORAL C5-C7PECTORAL MM

N. TO SUBCLAVIUS C5,6SUBCLAVIUS

MEDIAL PECTORAL C8,T1PECTORAL MM

THORACODORSAL C6-C8LATISSIMUS DORSI M

ROOTSTRUNKS

CORDS

ARM muscles - action on shoulder and elbow

Flexors (anterior compartment):

* biceps brachii (both joints) - supination and flexion of forearm - flexion of arm * coracobrachialis (shoulder joint) - flexion and add. of arm * brachialis (elbow joint) - flexion of forearm in all position

Extensors (posterior compartment):

* triceps brachii (both joints) - extension of forearm - extension of arm (long h.)

Anterior ( flexor) compartment Posterior (extensors) compartment

Long head of tricep

Important spaces of the shoulder region

Deltopectoral triangle – bounded by the clavicle superiorly, deltoidlaterally and the pectoralis major (clavicular head) medially. Cephalic vein and deltoid branch of thoracoacromial artery.

Quadrangular space – bounded superiorly by the teres minor and subscapularis, inferiorly by the teres major, medially by the long head of the triceps and laterally by the surgical neck of the humerus. Axillary nerve and posterior circumflex humeral artery and vein.

Triangular space – superiorly by the teres minor, inferiorly by the teres major and laterally by the long head of triceps. Circumflex scapular vessels.

Triangular interval - between the two heads of the triceps muscle, inferior to the teres major.Deep brachial artery and radial nerve.

12

3

1 – triangular space, 2 – quadrangular space, 3 – triangular interval

Brachial plexus injuries

Injuries to the brachial plexus affect movements (paralysis) and cutaneous sensation (anesthesia). Signs and symptoms depend on the part of the plexus involved.

Erb-Duchenne palsy is a paralysis of the arm caused by injury to the upper group of thearm's main nerves (specifically, spinal roots C5-C7), almost always occurring during birth. Depending on the nature of the damage, the paralysis can either resolve on its own over a period of months, necessitate physical therapy or require surgery.

Dejerine-Klumpke (Klumpkes) palsy refers to paralysis of the lower brachial plexus.A rare condition where a lower spine lesion causes paralysis of the forearm and hand muscles. The lesion may occur during birth or as a result of infection, tumor or trauma.

Questions of the day!

1. Which muscle is the primary supinator of the forearm? 1. Biceps brachii

2. Which muscle serves as the prime extensor of the forearm?1. Triceps

3. If a tumor grows into the quadrangular space of the axillary region, which structures would be in danger? (Axillary nerve, posterior circumflex humeral)1. Humeral loop2. Brachial plexus

4. ****Which artery may be damaged during the fracture of the shaft of the humerus?1. Posterior circumflex humeral artery