Axilla And Brachial Plexus

Front 1

Clavicle Osteology

Back 1

Doubly curved S shaped bone. Connects to upper limb of trunk.

Works like crane.

Sternal end is triangle, articulates with manubrium of sternum at sternoclavicular joint (SC).

Acromial end is flat and interacts with acromial end of scapula. This is the acromioclavicular joint (AC).

Helps transmit shock from upper limb to axial skeleton.

Front 2

Clavicle fracture

Back 2

Most frequent fracture. Happens during delivery.

80% through middle third of bone.

Obvious to diagnose: hold their arms. SCM elevates proximal fragment. Shoulder on affected side is slightly lower.

Front 3

Sternoclavicular joint

Back 3

"Saddle type" (looks like mini horse saddle). Synovial joint between clavicle and manubrium of sternum.

Only articulation between upper limb and the axial skeleton.

Hard to dislocate (strong articulation). This is key since heart is close.

Considerable motion despite the strength of articulation.

Front 4

Ligaments of Sternoclavicular joint

Back 4

Anterior and posterior SC ligaments.

Interclavicular ligament bridges the two clavicles.

Costoclavicular ligament anchors sternal end of clavicle to 1st rib.

There is also intraarticular disk, shock absorber. (foosh)

Front 5

Acromioclavicular joint

Back 5

Plane type (flat) synovial joint between acromion and clavicle.

Surrounded by loose fibrous capsule.

Ligaments help stabilize: AC ligament gives strength to AC joint, and coracoclavicular (extrinsic) ligaments (2, the trapezoid and conoid ligaments) unit coracoid process and clavicle.

Front 6

AC dislocation

Back 6

Injury of AC joint, common in sports.

Severity of ligament damage determines degree.
1: Sprain
2: Subluxation, tear AC ligament
3: Tear AC and both coracoclavicular ligaments. Leads to dislocation because of weight of arm.

Front 7

Four muscles that give medial rotation of arm

Back 7

1) Terres major
2) Pectoralis major
LOOK UP OTHERS

Front 8

Pectoralis Major

Back 8

Large fan shaped muscle in superior thorax.

Origin: Two, clavicular and sternocostal.

Insertion: Into lateral lip of intertubercular sulcus of humerus.

Adductor (lowers arms), Mediial rotator of humerus.

Innervated by medial and lateral pectoral nerves.

Front 9

Pectoralis Minor

Back 9

Located on anterior wall of axilla.

Triangular shaped muscle, goes from anterior surface of ribs 3-5 to to coracoid process of scapula.

Holds scapula against thoracic wall. Can also be used in respiration (when we lean over and pant).

Innervated by medial pectoral nerve.

Makes a bridge for neurovascular structures entering arm (brachial plexus,vein, axillary artery)

Front 10

Axillary artery

Back 10

Continuation of subclavian artery as it goes through lateral margin of 1st rib. Gives vascular supply to pectoral girdle/shoulder region.

Becomes brachial artery.

Divided into 3 by the pectoralis minor muscle (each side, plus under)

Front 11

Branching of Axillary Artery (6)

Back 11

1) Superior thoracic
2) Thoracoacromial trunk/lateral thoracic
3) Subscapular/anterior+posterior humeral circumflex

Front 12

Superior Thoracic Artery

Back 12

Offshoot of axilliary artery

Supplies intercostals.

Front 13

Thoracoacromial Trunk Artery

Back 13

Offshoot of axilliary artery

Feeds deltoid, acromial, pectoral and clavicular.

Front 14

Lateral Thoracic Artery

Back 14

Supplies pectoral muscles and breast

Front 15

Subscapular Artery

Back 15

Offshoot of axilliary artery

Feeds muscles around scapula. Gives rise to thoracodorsal artery/scapular circumflex (in triangular space)

Front 16

Anterior/Posterior Humeral Circumflex

Back 16

Offshoot of axilliary artery

Help feed humerus/muscles around there. Posterior is bigger, goes through quadrangular space.

Front 17

Axilla

Back 17

Pyramid shaped space between arm and thorax.
Passage for structures entering the upper limb.
Provides protection

Front 18

Brachial Plexus (basic structure/definition)

Back 18

Large nerve network, innervates upper extremities/muscles.

Structure organized into:
1) Roots
2) Trunks
3) Divisions
4) Cords
5) Branches

REAL TARHEELS DRINK COLD BEER!

Front 19

Roots of the brachial plexus

Back 19

Ventral rami of nerves C5 through T1. Form the roots.

Front 20

Trunks of brachial plexus

Back 20

C5 and C6 join to make superior trunk.
C7 makes middle trunk.
C8 and T1 make inferior trunk.

Front 21

Divisions of brachial plexus

Back 21

Each trunk splits into 2 divisions, A and P.
Anterior (A) divisions form nerves that innervate muscles in flexor (anterior) compartment of arm.

Posterior (P) muscles form nerves that innervate muscles in extensor (posterior) part of arm.

Front 22

Cords of brachial plexus

Back 22

Anterior divisions of superior and middle trunks form lateral cord.

Anterior division of inferior trunk continues as medial cord.

Posterior parts of all three trunks becomes posterior cord.

Front 23

Branches of brachial plexus

Back 23

Cords give rise to terminal branches.

Lateral cord becomes musculocutaneous and lateral root of median nerve.

Posterior cord gives rise to axillary and radial nerves.

Medial cord gives rise to medial root of medial nerve.

Front 24

Musculocutaneous nerve

Back 24

Innervates arm flexors

BBC

Biceps, brachialis, coracobrachialis

Front 25

Ulnar nerve

Back 25

Innervates muscles of the hand/some forearm flexors (flexor carpi ulnaris and 1.5 fingers of flexor digitorum profundis)

Front 26

Axillary nerve

Back 26

Innervates deltoid and teres minor.

Front 27

Radial nerve

Back 27

Innervates extensors of arm/forearm.

Front 28

Median nerve

Back 28

Innervates most forearm flexors and thenar (thumb) muscles.

Front 29

Other offshoots of brachial plexus

Back 29

From medial:
- Cutaneous brachial/antibrachial nerve
- Medial pectoral nerve
- Long thoracic nerve

From posterior cord:
- Upper/lower scapular nerve
- Thorcodorsal nerve

From lateral cord:
- lateral pectoral nerve
- suprascapular nerve

Front 30

Anatomy and location of brachial plexus

Back 30

Roots of plexus pass between anterior and middle scalene muscles. These arise from cervical vertebra, attach to 1st rib.

Front 31

More anatomy of brachial plexus

Back 31

Deep fascia surrounds scalene muscles, known as prevertebral fascia.

This extends and becomes axillary sheath.

Front 32

Intercostobrachial nerve

Back 32

Lateral cutaneous branch of T2 intercostal, innervates skin along medial arm. Only nerve from upper arm that does not innervate plexus. Hence blocking plexus (anesthetics) will NOT disable!!