posterior triangle, axilla, and brachial plexus

Question 1

brachial plexus

Answer 1

the nerves are branches from ventral primary rami of C5-T1 exiting via intervebral foramine; rami branch and recombine forming brachial plexus

Question 2

blood supply of the brachial plexus

Answer 2

from arteries branching from the aortic arch, the right brachipcephalic and left subclavian; vessels and nerves pass through two regions, the posterior triangle of the neck and the axilla

Question 3

posterior traingle of the neck

Answer 3

more lateral; shaped roughly like a pyramid and lies between the large superficial mucles of the neck, sternocleidomastoid and trapezius (upper fibers); the third side of the triangle is the middle third of the clavicle, between the attachment sites of these muscles

Question 4

boundaries of the posterior triangle

Answer 4

the posterior border of sternomastoid, anterior border of trapezius, and middle third of clavicle

Question 5

superficial fascia of the neck

Answer 5

contains the platysma

Question 6

platsyma

Answer 6

related to muscles of facial expression; innervated by a branch of the facial nerve (cranial nerve 7 or CN VII)

Question 7

cutaneous nerves of the posterior triangle

Answer 7

supply skin below and behind the vertex-ear-chin line, down to the superclavicular region; these are branches of C2 and C3, radiating fromna point about halfway along the posterior border of the sternomastoid

Question 8

external jugular vein

Answer 8

lies superficial to the sternomastoid

Question 9

nerve that supplies sternomastoid and trapezius

Answer 9

cranial nerve XI

Question 10

branch supplying the trapezius location

Answer 10

runs between the two layers of investing fascia across the posterior triangle.

Question 11

CN XI

Answer 11

only has motor fibers; sensory fibers are part of the ventral primary rami of C2-C4

Question 12

omohyoid

Answer 12

most inferior and most anterior muscles of the posterior triangle. it passes from the hyoid bone in the anterior f the neck to the scapula (omo=shoulder)

Question 13

deep to the omohyoid

Answer 13

a second triangle formed by anterior and middle scalene muscles and the first rib

Question 14

where does the anterior scalene attach

Answer 14

to a tubercle of the first rib.

Question 15

`prevertebral fascia

Answer 15

covers the scalene muscles, levator scapulae, and the splenius muscle

Question 16

subclavian artery and nerver components of the brachial plexus

Answer 16

pass between the anterior and middle scalene muscles and over the first rib to enter the axilla

Question 17

left subclavian artery

Answer 17

a direct branch of the aorta,

Question 18

right subclavian artery

Answer 18

passes behind the anterior scalene and goes over the first rib to become an axillary artery

Question 19

axillary artery

Answer 19

crosses the teres major muscle to enter the arm as the brachial artery, the main supply to the upper limb.

Question 20

phrenic nerve

Answer 20

(C3-5 to the diaphram) lies on the anterior surface of scalenus anterior, and is therefore at risk when anesthetic is injected into this region

Question 21

thyrocervical trunk

Answer 21

deep to sternomastod; arises from the subclavian artery

Question 22

transverse cervical and suprascapular arteries

Answer 22

arise in turn from the thyrocervical trunk; these arteries cross the posterior triangle to supply posterior muscles associated with the scapla: trapezius, the rhomboids, supraspinatus and infraspinatus; the arteries cross scalenus anterior superficial to the phrenic nerve

Question 23

axillary vein

Answer 23

drains the upper limb, crosses the 1st rib to become the subclavian vein, and combines with the internal jugular vein draining the head to form the brachiocephalic vein

Question 24

scalenus anterior

Answer 24

attaches to the first rib and separates the subclavian artery (posterior) from the subclavian vein (anterior)

Question 25

how nerves and blood vessels leave the posterior traingle and enter the apex of the axilla

Answer 25

through the cervioaxillary canal, which is a triangle bounded by the middle of the clavicle, the first rib and the upper border of the scapula

Question 26

anterior border of the axilla

Answer 26

a fold of skin covering the lower border of pectoralis major

Question 27

posterior border of the axilla

Answer 27

a fold of skin covering the latissimus dorsi, teres major, and subscapularis muscles

Question 28

lateral border of the axilla

Answer 28

bicipital groove of the humerus

Question 29

pectoralis major

Answer 29

attaches to the lateral lip of the bicipital groove of the humerus

Question 30

medial border of the axilla

Answer 30

the chest wall (ribs 1-4) covered by serratus anterior

Question 31

floor of the axilla

Answer 31

a sheet of tough fascia that bridges between the anterior and posterior folds

Question 32

vertical sheet of clavipectoral fascia

Answer 32

attaches to the clavicle and splits around the subclavius and pectoralis minor muscles

Question 33

suspensory ligament

Answer 33

a portion of the clavipectoral fascia; attaches to the fascia of the floor and raises the skin between the anterior and posterior borders into a dome - the armpit

Question 34

veins of the axilla

Answer 34

two veins lie in the superficial fascia of the upper limb and have no accompanying arteries; these are like the saphenous veins of the lower limb; the cephalic vein (named for its use in blood-letting to relive headaches) lies on the lateral side of the forearm and arm, closer to the head when the upper limb is abducted at the shoulder; the basilic vein (closer to the base) is superficial in the forearm but becomes the deep vein of the arm, accompanying the brachial artery; it continues into the axilla and becomes the axillary vein. the cephalic vein runs in the deltopectoral groove, between the deltoid and pectoralis major muscles, together with a branch of the thoracoacromial artery; the cephalic vein then pierces the clavipectoral fascia to join the axillary vein; a superficial vein must pierce the deep fascia at some point to join the system of deep veins

Question 35

lymph channels and lymph nodes of the axilla

Answer 35

these are divided into groups according to their locatio; lateral nodes receive lymph from the upper limb via channels along the axillary vein; pectoral nodes receive drainage from the thorax and are an important site of breast cancer metastasis subscapular nodes (lying posterior) lie anterior to (deep to) the scapular lymph from all fo these groups of nodes drains first into central nodes, then in apical nodes located along the axillary vein. lymph from apical nodes on the right side drainsinto the subclavian trunk, while lymph on the left side drains into the throacic duct; the subclavian trunk and the thoracic duct join the venous system at the junction of the internal jugular and subclavian veins

Question 36

muscle in the axilla

Answer 36

coracobrachialis and the short head of the biceps both arise from the carcoid process of the scapula and pass from the axilla to the arm.

Question 37

vascular contents of the axilla

Answer 37

subclavian artery and vein become the axillary artery and vein as they pass laterally over the first rib; for branches of axillary artery, it's covenient to divide the artery into three parts, lying medial to, deep to, and lateral to, the pectoralis minor muscle. from the first part arise the superior (or supreme) thoracic, a small branch to the upper thorax that anastomoses with intercostal arteries.

Question 38

thoracoacromial artery

Answer 38

supplies the nearby pectoral and deltoid muscles, the acromian and the clavicle.

Question 39

lateral thoracic artery

Answer 39

supplies nearby muscles of the lateral thorax, latissimus dorsi and serratus anterior

Question 40

collateral circulation

Answer 40

an additional channel for blood that can compensate for a prtial block in the main channel

Question 41

arterial anastomoses

Answer 41

are common features of limb joints; allow collateral circulation

Question 42

anterior and posterior circumflex humeral arteries

Answer 42

wind around the humerus

Question 43

subscapular artery

Answer 43

supplies the subscapuls

Question 44

suprascapular artery

Answer 44

supplies the scapula

Question 45

circulation between the subclavian and axillary arteries

Answer 45

the suprascapular artery and the circumflex scapular artery anatomose with each other - dorsal scapular artery also participates in the anastomosis

Question 46

dorsal scapular artery

Answer 46

supplies the rhoboids

Question 47

collateral circulastion

Answer 47

an additional channel for blood that can compensate for a partial block in the main channel arterial anatosomes allowing collateral circulation are common features of limb joints. other examples are found at elbow, hip, and knee joints

Question 48

basic motions at the shoulder, elbow, wrist and finger joints

Answer 48

extension and flexion

Question 49

flexion

Answer 49

performed by flexor muscles on the anterior side of the limb

Question 50

extension

Answer 50

performed by extensor muscles on the posterior side of the limb

Question 51

flexor muscle nerves

Answer 51

supplied by nerves on the anterior side of the limb

Question 52

extensor muscle nerves

Answer 52

supplied by nerves on the posterior side of the limb

Question 53

roots of the brachial plexus

Answer 53

ventral primary rami of spinal nerves C5 through T1, leaving intervertebral foramina; they are stacked on top of one another in a vertical plane in the neck

Question 54

trunks of the brachial plexus

Answer 54

as the roots pass into the posterior triangle, they form trunks still stacked in a vertical plane; C5 and C6 combine to form the upper trunk, C7 continues as the middle trunk, while C8 and T1 combine to form the lower trunk

Question 55

branches from anterior divisions of the trunks

Answer 55

will supply anterior compartment muscles (flexors)

Question 56

branches from posterior division of the trunks

Answer 56

will supply posterior compartment muscles (extensors)

Question 57

posterior cord

Answer 57

the three posterior division combine to form the posterior cord

Question 58

lateral cord

Answer 58

anterior division from the lower trunk forms the medial cord; made clear by standing in the anatomical position and abducting the upper limb; nerves from higher trunks (upper and middle) project out the (higher) lateral side of the arm, while nerves from the lower trunk become medial (lower side) on the arm

Question 59

2 general principles of nerves derived from the brachial plexus

Answer 59

1) more proximal muscles lie closer to the midline of the body and are supplied by nerves that arise from more proximal portions of the plexus 2) the most proximal muscles of the upper limb are located on the trunk and move the scapula as well as the humerus. these include pectoralis major and minor, latissimus dorsi, the rhomboids, levator scapulae, and serratus anterior

Question 60

nerves from the roots of the brachial plexus

Answer 60

dorsal scapular - C5 supplies rhomboids and levator scapulae, located high on the posterior chest wall (dorsal side of the body) long thoracic - C5, C6, C7 supplies serratus anterior, located lower on the lateral chest wall

Question 61

nerves from the upper trunk of the brachial plexus

Answer 61

nerve to subclavius - to a small muscle just below the clavicle suprascapular nerve - to supraspinatus and infraspinatus, muscles located on the superficial surface of the scapula. The suprrascapular artery supplies the same muscles

Question 62

nerves from the lateral cord (to anterior muscles and skin)

Answer 62

lateral pectoral nerve - to pectoralis major musculocutaneous nerve - to flexor muscles of arm, then the lateral cutaneous nerve of forearm lateral contribution to median nerve (anterior nerve of forearm and hand)

Question 63

nerves from the medial cord (to anterior muscles and skin)

Answer 63

medial pectoral nerve - to pectoralis major and minor medial cutaneous nerves of arm and forearm medial contribution to median nerve ulnar nerve - medial side of forearm and hand

Question 64

nerves from posterior cord (to posterior muscles and skin)

Answer 64

upper and lower subscapular nerves to subscapularis muscle and teres major thoracodorsal nerve to latissmus dorsi, located on dorsal side of thorax radial nerve to posterior extensor muscles of arm and forearm axillary nerve to deltoid and teres mino mnemonic ULTRA

Question 65

nerves in anterior divisions of C5-C6

Answer 65

run primarily in the multocutaneous nerve and supply more proximal muscles of the arm

Question 66

nerves in anterior divisions of C7-C8

Answer 66

run primarily in the median nerve and supply more distal muscles of the forearm and hand (primarily the thumb)

Question 67

nerves in anterior divisons of T1

Answer 67

run primarily in the ulnar nerve and supply distal muscles of the forearm and especially the intrinsic muscles of the hand

Question 68

upper brachial plexus injury (C5-C6)

Answer 68

caused by stretching of nerves associated with pulling the head away from the shoulder; e.g. difficult forceps deliveries and motorcycle accidents damage to C5 and C6 fibers impairs function of proximal muscles - supraspinatus, deltoid, biceps and brachialis loss of deltoid as an abductor lets the upper limb fall close to the side; loss of the biceps, the strong supinator, causes forearm to be pronated, the "waiter's tip" position; the condition is Erb's palsy.

Question 69

lower brachial plexux injury (C8-T1)

Answer 69

often caused by hyperabducting the arm, as in grabbing something overhead to avoid a fall; T1 supplies intrinsic muscles of the hadn which control movement at the metacarpophalangeal joints; a "claw hand" results from hyptextension of the fingers at the MP joints; the condition is called Klumpke's palsy.