Lec 8 Brachium and Plexus Flashcards
Biceps Brachii
MA: Supinates forearm, flexes forearm
PA: Short heard; coracoid process, Long head; Supraglenoid Tubercle and Labrum, Short head resists shoulder dislocation
DA: Radial Tuberosity and Forearm fascia via bicipital aponeurosis
N: Musculocutaneous N C5, *C6, C7
Coracobrachialis
MA: Flex and Adduct the Shoulder
PA: Coracoid process
DA: Middle third of Medial surface of humerus
N: Musculocutaneous C5,*C6, C7
Brachialis
MA: Flex elbow in pronated forearm position (all positions)
PA: Distal end of anterior humerus
DA: Ulnar tuberosity and Coronoid process of Ulna
N: Musculocutaneous C5 C6 and Small branch from Radial C5 C7
Brachioradialis
MA: Flexes elbow in mid-pronated position (thumb up, humeroulnar joint)
Assists in pronating and supinating the forearm when these movements are resisted from the end range
PA: lateral supracondylar ridge of humerus
DA: Lateral distal end of radius proximal to styloid process
N: Radial Nerve C5, *C6, C7
Which muscle is the strongest elbow flexor?
Brachialis
Triceps Brachii
MA: Chief extensor of forearm/elbow
Long head resists dislocation of humerus, especially during adduction
PA:
- Longhead; infraglenoid tubercle (of scap)
- Lateral Head; posterior surface, superior to radial groove
- Medial Head; posterior humerus, inferior to radial groove
DA: Olecranon of ulna
N: Radial Nerve C6, *C7, *C8
Boundaries of the Axilla
“armpit”
apex - armpit
base - formed by skin
anterior wall - pec minor and major
lateral wall - upper portion of humerus
medial wall - serratus anterior and rib cage (*since the pec minor is visible in cross section, the rub must be 3-5)
posterior wall - lat, subscapularis and teres major
What muscle that attaches to the axilla region is the farthest away from the axilla region?
Lat
Where is the PNS CNS division for spinal nerves
Spinal Nerve (made by anterior and posterior roots) are CNS
Rami are PNS
so if anterior rami are damaged, the CNS is not affected potentially (something like that)
How many of each RTDCB are there
5 Rami (C5, 6, 7, 8 T1)
3 Trunks (superior, middle and inferior)
6 Divisions (3 anterior and 3 posterior)
3 Cords (lateral, Posterior and medial)
Branches - 5 main terminal
Where do the following nerves come off the brachial plexus?
Dorsal Scapular
Lower and Upper Subscapular
Lateral Pectoral
Thoracodorsal
Long thoracic
Medial Pectoral
First intercostal
Nerve to subclavius
Suprascapular
Medial Cutaneous
Dorsal Scapular - C5 rami
Lower and Upper Subscapular - Posterior Cord
Lateral Pectoral - Lateral Cord
Thoracodorsal - Posterior Cord
Long thoracic - Rami if C5, C6, C7
Medial Pectoral - Medial Cord
First intercostal - T1 rami
Nerve to subclavius - Superior trunk
Suprascapular - Superior trunk
Medial Cutaneous - Medial Cord
Where do the 5 terminal branches go? What muscles do they innervate?
Musculocutaneous - anteriorly emerges at armpit and innervates biceps brachii, coracobrachialis and brachialis
Median N - anterior, medial to musculocutaneous, innervates anterior forearm muscles
Ulnar N - anterior, medial, goes all the way down to ulna, also innervates some medial forearm flexors
Axillary N - comes down through posterior scapular and wraps around upper humerus, innervates deltoid and teres minor
Radial N - comes posteriorly through scapula and travels down to posterior humerus, innervates triceps
Subclavius
MA: depresses and anchors clavicle
PA: junction of first rib and its costal cartilage
DA: inferior surface of middle surface of clavicle
N: the nerve to subclavius C5 C6
Contents of Thoracic Outlet
Brachial Plexus, subclavian vein and artery, (turn into axillary artery and vein after first rib), scalenes
Anterior Scalene
MA: Flex neck laterally, elevate first rib during forced inhaltion
SA: TP od C3-6
IA: first rib
N: cervical spinal nerve C4-C6
Middle Scalene
MA: flex neck laterally and elevate first rib during forced inhalation
SA: TP of C5-C7
IA: 1st rib
N: anterior rami of cervical spinal nerves
Posterior scalene
MA: flex nick laterally and elevate the SECOND rib during forced inhalation
SA: TP of C5-C7 posterior tubercles
IA: external border of second rib
N: anterior rami of cervical spinal nerves C7 and C8
Where does the brachial plexus exist in relation to the scalene muscles
exits between the anterior and middle scalene
Thoracic Outlet Syndrome
compression of nerves arteries or veins in the thoracic outlet region
typically occurs via compression between the clavicle and 1st rib, pec minor or the presence of a cervical rib (variation in a few people of rib off of C7 very tiny)
causes pain, weakness, numbness, muscle atrophy and swelling
symptoms will be a peripheral nerve distribution because if the brachial plexus is compressed, those are Rami, which begins the PNS division
What are the three spaces/intervals of the Upper Extremity
Quadrangular space
Triangular Space
Triangular Interval
Quadrangular space fxn and contents
an anatomical conduit for neurovascular strucutures to pass from the anterior axilllary region to the posterior scapular region
axillary nerve, and posterior circumflex HUMERAL artery and vein
Quadrangular space borders
pointing in
top; inferior margin of teres minor
lateral side; surgical neck of humerus
bottom: superior border of teres major
apex: lateral margin of the long head of the triceps brachii
Triangular space borders and contents
pointing in
lateral side: the medial margin of the long head of the triceps brachii
top: inferior margin of teres minor
bottom: superior border of teres major
content: circumflex SCAPULAR artery and vein
Triangular interval borders and contents
upside down
medial border: lateral margin of long head of triceps brachii
lateral border: shaft of humerus
superior border: inferior margin of teres major
contents: profunda brachii artery and radial nerve
What are the two divisions of the upper extremity
brachium
antebrachium (forearm)
What is the only synovial joint articulation between the UE to the axial skeleton?
sternoclavicular joint
What is a Proximal bicep rupture
popeye sign - the muscle belly to slide down and bunch up in arm
For distal ruptures, surgery is not typically done because it is a cosmetic issue
Innervation and function of Musculocutaneous nerve AND LEVELS
Has motor AND sensory innervation
Motor innervation to all muscles of the anterior compartment of the upper arm
Sensory innervation to the skin of the lateral forearm
C6, C6 C7
Contents of Extensor compartment
one muscles - triceps
deep brachial artery - branch off brachial artery that goes to posterior side
radial nerve C5-T1
How can you tell if you are looking at posterior or anterior humerus?
If you see the radial groove, its the posterior side, that where triceps attach around
Another name for deep brachial artery (whats its parent structure)
profunda brachii artery
comes off brachial artery
What does the radial nerve innervate? what LEVELS
supplies the entire posterior compartment
C5, C6, C7 C8 T1
Axillary N Levels
C5 C6
