Pectoral Region and the Brachial Plexus

Question 1

The upper limb has several important transition areas that provide passage and protection to structures

Answer 1

The axilla is an irregularly shaped pyramidal area for passage of major neurovascular structures from the neck to the arm

Cubital fossa (anticubital) is a triangular depression anterior to the elbow for passage of the brachial artery and median nerve

Carpal tunnel represents a gateway to the palm for the 9 long flexors tendons and the median nerve

Question 2

Acromial end of the clavicle articulates with the acromion of the scapula at the ______

Answer 2

acromioclavicular joint (AC)

Question 3

Sternal end articulates with the manubrium of the sternum at the

Answer 3

sternoclavicular joint (SC)

Question 4

Clavicle Fractures

Answer 4

Most frequently fractured bone in body

80% of adult fractures are through the middle 1/3rd of bone

Clinically obvious fractures-patients hold and support arm

SCM elevates proximal fragment

Shoulder on affected side is usually lower than other side

Can fracture in babies during labor/delivery as shoulders traverse the birth canal

Question 5

synovial joint between the clavicle and the manubrium of the sternum

Answer 5

Sternoclavicular Joint (SC)

Question 6

SC joint capsule is reinforced by strong _______ ligaments (essentially thickened portions of the joint capsule) along with the _____________ which courses along the superior aspect of both joints and the manubrium

Answer 6

anterior and posterior sternoclavicular; interclavicular ligament

Question 7

________ anchors sternal end of the clavicle to the 1st rib

Answer 7

Costoclavicular ligament

Question 8

nNumerous ligaments help strengthen the AC joint:

Answer 8

1. Acromioclavicular ligament-provides superior strength to the joint capsule
2. Coracoclavicular “extrinsic” ligaments- strong pair of ligaments that unites coracoid process and the clavicle (trapezoid & conoid ligaments)
3. Coracoacromial ligament (arch)- courses between the coracoid and acromion processes

Question 9

nSynovial joint between the acromion and clavicle

n

nSurrounded by a loose fibrous capsule

Answer 9

Acromioclavicular Joint (AC)

Question 10

3rd degree AC injuries (sometimes refered to as _____ because

Answer 10

“shoulder separations”) - the shoulder separates or falls away from the clavicle due to the weight of the arm

Question 11

4 thoracoappendicular muscles

Answer 11

pectoralis major

pectoralis minor

subclavius

serratus anterior

Question 12

pectoralis major inserts into the

Answer 12

Inserts into the lateral lip of the intertubercular sulcus (bicipital groove) of the humerus

Question 13

pectoralis major is innervated by

Answer 13

nInnervated by the medial & lateral pectoral nerves

Question 14

pectoralis minor Inserts into the _____of the scapula

Answer 14

coracoid process

Question 15

the pectoralis minor is innervated by

Answer 15

Innervated primarily by the medial pectoral nerve

Question 16

The pectoralis minor forms a “bridge” over the major neurovascular structures entering the arm:

Answer 16

1. Axillary artery
2. Axillary vein
3. Brachial plexus

Question 17

§ Continuation of the

subclavian artery as it

passes the lateral

margin of the 1st rib

§ Provides vascular supply

to the pectoral girdle

and shoulder region

Divided into three parts

by the pectoralis minor muscle

§ Continues into the arm as the

brachial artery as it passes

lateral to the teres major muscle

Answer 17

Axillary Artery

Question 18

n3rd part of axillary artery has three branches

Answer 18

1. Subscapular
2. Anterior humeral circumflex
3. Posterior humeral circumflex

Question 19

Subscapular- largest branch supplies

Answer 19

muscles and anastomoses around the scapula, gives rise to the thoracodorsal artery and the scapular circumflex (triangular space)

Question 20

Anterior & Posterior Humeral circumflex- help vascularize the

Answer 20

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

Question 21

Many of these branches of the axillary artery contribute

to a large “anastomotic arcade”

that provides collateral circulation

around the _____

Answer 21

scapula/muscles

Question 22

“Real Tarheels Drink Cold Beer”

Answer 22

Question 23

The roots are Formed by the ventral rami of

_______ spinal nerves

Answer 23

C5 through T1;

These ventral rami of

C5-T1 form the “roots”

or the “origins” of the

brachial plexus

Question 24

The roots of the brachial plexus

then unite to form 3 trunks:

Answer 24

C5 & C6 unite to form the

superior trunk

C7 forms the middle trunk

C8 & T1 unite to form the

inferior trunk

Question 25

C5 & C6 unite to form the

______

Answer 25

superior trunk

Question 26

C7 forms the ____

Answer 26

middle trunk

Question 27

C8 & T1 unite to form the

____

Answer 27

inferior trunk

Question 28

Each trunk then divides into an ________

Answer 28

anterior & posterior division

Question 29

Anterior (A) divisions

eventually form nerves that

innervate muscles in ____

Answer 29

flexor

(anterior) compartments of

the upper limb

Question 30

Posterior (P) divisions

combine and eventually form

nerves that innervate muscles in

_______

Answer 30

extensor (posterior)

compartments of the upper limb

Question 31

Anterior divisions of the

superior & middle trunk

unite to form the

____

Anterior divisions of the

inferior trunk continues

as the _____

Posterior divisions of all three trunks

unite to form the _____

Answer 31

lateral cord; medial cord; posterior cord

Question 32

innervates deltoid & teres minor

Answer 32

Axillary Nerve-

Question 33

innervates flexors of the arm

Answer 33

Musculocutaneous

Question 34

_____ intrinsic muscles of the hand and

some forearm flexors

Answer 34

Ulnar Nerve

Question 35

_____ innervates extensors of the arm & forearm

Answer 35

Radial Nerve

Question 36

innervates most forearm flexors and thenar (thumb) muscles

Answer 36

Median Nerve

Question 37

Subscapular nerves all innervate muscles that

_____

Answer 37

adduct and medially rotate the arm

Question 38

Cords of the plexus are named in relationship to the _____ (medial, lateral, and posterior)

Answer 38

axillary artery

Question 39

Posterior dislocations of the _____can compress the great vessels and/or trachea

Answer 39

sternoclavicular joint (SC)

Question 40

AC dislocations (sometimes called “separations”) results from injury to the AC joint with rupture of the _____ ligaments

Answer 40

coracoclavicular

Question 41

The roots of the plexus and the subclavian artery pass between the ______ muscles in the cervical region

Answer 41

anterior and middle scalene

Question 42

The deep fascia that surrounds these scalene muscles in the neck is called the ______

Answer 42

prevertebral fascia

Question 43

The prevertebral fascia extends laterally as the axillary sheath forming a tubular sheath that surrounds the _____

Answer 43

brachial plexus and axillary artery

Question 44

______ a lateral cutaneous (sensory) branch of the T2 intercostal nerve that supplies a small region of skin sensation along the medial aspect of the arm

Only nerve to the upper limb that does not originate from the plexus (USMLE Step 1 question

Brachial plexus nerves blocks (often performed prior to surgery on the upper limb) will NOT anesthetize this nerve

Answer 44

Intercostobrachial Nerve

Question 45

Dermatomes

Answer 45

Dermatomes are representations of which spinal nerve innervates a specific region of the skin

or…

the area of skin innervated by a spinal cord level is known as a dermatome

In other words, sensory information (pain, touch temp) from the thumb and lateral arm (the C6 dermatome) returns to the spinal cord via the C6 spinal nerve and enters the C6 spinal cord level/segment

Sensory information from your little toe area (the S1 dermatome) returns to the spinal cord via the S1 spinal nerve and enters the S1 spinal cord level/segment (which happens to be at about the L1 vertebral column level)

Question 46

C5-

C6-

C7-

C8-

T1-

Answer 46

C5- tip of shoulder

C6- thumb

C7- middle finger

C8- little finger

T1- medial arm

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