10.18 Upper Limb: Pectoral Region And Brachial Plexus

Front 1

clavicle

Back 1

doubly curved, "S" shaped long bone that connects the upper limb to the trunk or axial skeleton

Front 2

function of the clavicle

Back 2

1. serves as a moveable strut allowing the scapula to move freely along the thoracic wall
2. helps transmit shock from the upper limb to the axial skeleton

Front 3

sternal end of the clavicle articulates with what?
at what joint?

Back 3

the manubrium of the sternum at the sternoclavicular joint (SC)

Front 4

acromial end of the clavicle articulates with what?
at what joint?

Back 4

the acromion of the scapula at the acromioclavicular joint (AC)

Front 5

sternoclavicular joint

Back 5

- "saddle type" synovial joint between the clavicle and the manubrium of the sternum
- only true articulation between the upper limb and the axial skeleton
- extremely strong - rarely dislocates

Front 6

ligaments that reinforce the sternoclavicular joint capsule (4)

Back 6

1/2. anterior and posterior sternoclavicular ligaments - STRONG, thickened portions of the joint capsule
3. interclavicular ligament - courses along superior aspect of joints and the manubrium
4. costoclavicular ligament - anchors sternal end of clavicle to the 1st rib

Front 7

acromioclavicular joint

Back 7

- "plane type" synovial joint between the acromion and clavicle
- surrounded by a loose fibrous capsule

Front 8

ligaments that reinforce the acromioclavicular joint (3)

Back 8

1. acromioclavicular ligament - superior strength to joint capsule
2. coracoclavicular "extrinsic" ligaments - pair of ligaments (trapezoid and conoid ligaments), unites coracoid process and the clavicle
3. coracoacromial ligament (arch) - courses between the coracoid and acromion processes


*injuries of the AC joint are relatively common, graded according to severity of ligamentous damage (1st (sprain), 2nd (subluxation), 3rd (shoulder separations/dislocations, all 3 ligaments torn)

Front 9

pectoralis major: origin

Back 9

clavicular and sternocostal heads

Front 10

pectoralis major: insertion

Back 10

lateral lip of the intertubercular sulcus of the humerus

Front 11

pectoralis major: action

Back 11

1. medial (internal) rotator of the arm
2. adductor and flexor of the arm

Front 12

pectoralis major: innervation

Back 12

medial and lateral pectoral nerves

Front 13

pectoralis minor: origin

Back 13

anterior surface of the 3rd-5th ribs

Front 14

pectoralis minor: insertion

Back 14

coracoid process of the scapula

Front 15

pectoralis minor: action

Back 15

1. stabilizes the scapula against the thoracic wall
2. accessory respiratory muscle

Front 16

pectoralis minor: innervation

Back 16

medial pectoral nerve

*the pectoralis minor forms a "bridge" over the major neurovascular structures entering the arm: axillary artery, axillary vein, and brachial plexus

Front 17

subclavius: location

Back 17

along the inferior surface of the clavicle

Front 18

subclavius: action

Back 18

1. stabilize the clavicle and sternoclavicular joint throughout its range of motion
2. provides protection to underlying neurovascular structures (brachial plexus and subclavian vessels) if clavicle is fractured

Front 19

axillary artery
- continuation of what?
- provides vascular supply where?
- divided into three parts by what muscle?
- continues into the arm as the what?

Back 19

- continuation of the subclavian artery as it passes the 1st rib
- provides vascular supply to the pectoral girdle and shoulder
- divided into 3 parts by the pectoralis minor muscle
- continues into the arm as the brachial artery as it passes lateral to the teres major muscle

Front 20

number of branches that arise from the axillary artery

Back 20

6

Front 21

1st part of the axillary artery (portion before the pectoralis minor) has how many branches? name(s)?

Back 21

one branch - superior thoracic artery

Front 22

2nd part of the axillary artery (portion underneath the axillary artery) has how many branches? name(s)?

Back 22

two branches: thoracoacromial trunk and lateral thoracic artery

Front 23

3rd part of the axillary artery (past the pectoralis minor but before the brachial artery) has how many branches? name(s)?

Back 23

three branches: subscapular, anterior humeral circumflex, and posterior humeral circumflex

Front 24

subscapular axillary artery distribution

Back 24

largest branch supplies muscles and anastamoses around the scapula, gives rise to the thoracodorsal artery and the scapular circumflex (triangular space)

Front 25

anterior and posterior humeral circumflex

Back 25

help vascularize the humerus and surrounding muscles (posterior courses through the quadrangular space)

Front 26

if the axillary artery is blocked (thrombosis), will the arm receive blood?

Back 26

yes! the numerous blood vessels that anastomose around the scapula can convey blood to the arm

Front 27

brachial plexus

Back 27

large nerve network that innervates the upper extremity and all its associated musculature

Front 28

5 segments (regions) of the brachial plexus

Back 28

1. roots
2. trunks
3. divisions
4. cords
5. branches

Front 29

roots of the brachial plexus are formed by what?

Back 29

ventral rami of C5 through T1 spinal nerves

Front 30

roots give rise to __ trunks: ___, ___, and ___

Back 30

3 trunks: superior (C5 and C6), middle (C7), and inferior (C8 and T1)

Front 31

trunks divide into ___ and ___ divisions

Back 31

anterior and posterior divisions

*anterior divisions eventually form nerves that innervate muscles in flexor (anterior) compartments of the upper limb
*posterior divisions combine and form nerves that innervate muscles in extensor (posterior) compartments of the upper limb

Front 32

divisions unite to form the __ ___ ___

Back 32

3 main cords (lateral, posterior, and medial)

*lateral cord - from anterior divisions of the superior and middle trunk
*medial cord - from the anterior divisions of the inferior trunk
*posterior cord - posterior divisions of all three trunks

Front 33

cords give rise to the __ ___ ____

Back 33

5 terminal branches

Front 34

lateral cord gives rise to what? (2 things)

Back 34

1. musculocutaneous
2. lateral root of the median nerve

Front 35

posterior cord gives rise to what? (2 things)

Back 35

1. radial nerve
2. axillary nerve

Front 36

the medial cord gives rise to what? (2 things)

Back 36

1. ulnar nerve
2. medial root of the median nerve

Front 37

5 major terminal nerve branches of the brachial plexus (and innervations)

Back 37

1. musculocutaneous - innervates flexors of arm
2. axillary nerve - innervates deltoid and teres minor
3. radial nerve - innervates extensors of arm and forearm
4. median nerve - innervates most forearm flexors and thumb muscles
5. ulnar nerve - intrinsic muscles of the hand and some forearm flexors

Front 38

the roots of the plexus (and the subclavian artery) pass between the _____ muscles

Back 38

anterior and middle scalene muscles
- these arise from cervical vertebrae and insert onto the first rib

Front 39

fascia that surrounds the scalene muscles in the neck

Back 39

prevertebral fascia

Front 40

the prevertebral fascia extends laterally as the ___, forming a tubular sheath that surrounds the ___ and the ___

Back 40

axillary sheath
- surrounds the brachial plexus and axillary artery

Front 41

the cords of the plexus are named according to their location relative to the ___

Back 41

axillary artery
- lateral cord, medial cord, and posterior cord

Front 42

the only nerve to the upper limb that does not originate from the plexus (step 1 favorite!)

Back 42

intercostobrachial nerve - sensory branch of the T2 intercostal nerve that supplies a small region of skin sensation along the medial aspect of the arm
- brachial plexus nerve blocks will NOT anesthetize this nerve

Front 43

pre-fixed brachial plexus

Back 43

plexus has a large contribution from C4, but lacks T1

Front 44

post-fixed brachial plexus

Back 44

plexus lacks C5 but has large T2 contribution

Front 45

bottom line concept: AC dislocations (aka separations) result from injury to...

Back 45

the AC joint with rupture of the coracoclavicular ligaments

Front 46

bottom line concept: axillary artery is divided into three parts by...

Back 46

the overlying pectoralis minor muscle

Front 47

bottom line concept: subdivisions of the brachial plexus can be remembered as what?

Back 47

Real Tarheels Drink Cold Beer
(Roots, Trunks, Divisions, Cords, Branches)

Front 48

bottom line concept: cords of the plexus are named in relationship to what?

Back 48

the axillary artery (thus they are named: medial, lateral, and posterior)

Front 49

bottom line concept: the brachial plecus and subclavian artery course between what two muscles?

Back 49

the anterior and middle scalene muscles