Lec 9 Pec Region and Shoulder Flashcards
Origin of dermatomes and myotomes of the limbs
3rd week of embryogenesis
day 20 - mesoderm differentiation, types are close to neural tube
after day 20 - mesoderm differentiates into 44 pairs of somite’s which change into 31 sets to correspond with the 31 spinal nerves from neural tube
somites subdivide into sclerotome (precursor to cartilage and bone) and the DERMOMYOTOME which will divide into myotome and dermatome creating segmental innervation
When does segmental distribution of myotomes occur?
6 weeks (embryogenesis)
fusion of myotomes extending into the limbs produces skeletal muscles with multisegmented innervation
what does this indicate?
If c5 where to be damaged, other spinal nerves innervated that muscle (that had fused together) can take over the motion
What happens at the fourth week of development?
upper limb buds start to appear as elevations of the C5-T1
the tip of the arm bud (elevation) is called the apical ectodermal ridge; AER)
What emerges after the arm buds?
About one week after later (week 5) starting from cranial to caudal the lower limb buds appear L2-S2 segments
How are the limbs oriented during early development?
distal limb buds flatten into paddle-like hand and foot plates with thumb and great toe cranially and palms and soles anteriorly
flexures - limbs bend anteriorly, the elbow and knee are directed laterally, causing palm and sole to be directed toward the trunk
What happens at end of 7th week of development? (Limb development)
proximal parts of the upper and lower limbs undergo 90 degree torsion around their long axis in OPPOSITE directions
elbow becomes directed caudally (elbow points down)
and knee cranially (knee points up)
What happens to the lower limb in addition to proximal segment torsion? (where the knee goes cranially)
Permanent pronation (twisting) of the leg = foot becomes oriented with the great toe on the medial side
AKA rotates foot to be flat on floor, great toe is now medial whereas the thumb still remains lateral in anatomical position)
Describe the formation of the digits process
as elgonation continues, the mesenchyme condenses into plates forming the cartilaginous models of the future digital bones
the AER then breaks up and is maintained only over the tips of the future digits
interdigital spaces are progressively made via cellular apoptosis
Syndactyly
- dactyly
represents fusion of two or more digits, can be isolated finding or part of a syndrome
Polydactyly
extra digits, typically occurs bilaterally
Macrodactyly
enlarged digits
Adactyly
absence of digits
Ectrodactyly
lobster claw deformity, typically missing middle digit, typically unilaterally
Amelia
complete absence of one or more extremities
Meromelia
partial absence of one or more extremities
Phocomelia
shortened lower extremities
Radial longitudinal deficiency
radius is shortened (underdeveloped or absent)
What is a Synovial Joint vs Fxnal Joint?
Synovial
- distal end of two bones articulate
- articular cartilage
- articular capsule (outer fibrous layer and inner synovial membrane with synovial fluid)
Functional joint;
- no joint cavity
- held together by soft tissue
What are the 4 joints of the upper extremity?
Glenohumeral Joint (synovial)
Acromial clavicular (synovial)
Sternoclavicular (synovial)
Scapulothoracic joint (FUNCTIONAL), scapular and rib cgaes and joining muscles
Where is the subacromial space located? What is its significance?
Located under the acromion process of scap (if looking laterally, it will be the big open space)
Contains rotator cuff ligaments
Biceps tendon
Glenohumeral ligament
Shoulder joint capsule
Bursa
Where is the spinoglenoid notch located?
laterally on the posterior aspect of the scapula, just below the spine of the scapula, and leads into the glenoid fossa
(passage for the suprascapular nerve and the suprascapular artery)
Which end of the clavicle is flat?
Sternal end is flat, has the sternal facet
Acromial end is not flat
Know the other bony landmarks for clavicle
What is special about the 5 terminal branches of the brachial plexus?
All 5 are muscle AND skin innervated
Not referring to dermatomes and myotomes here, those are spinal levels. We are looking at peripheral nerves
Which 3 muscles attach to the coracoid process
pec minor
biceps brachii
coracobrachialis
What ligament keeps the biceps in their groove?
Transverse humeral ligament
runs between greater and lesser tubercles of humerus creating a “bridge” over a the bicipital (intertubercular) groove
biceps long head (tendon) runs through the groove and under the ligament
What muscles of the brachium are tricarticulate?
long head of triceps
biceps long and short head
Know slide 28 - Vascular
What are the parent structures for the right and left common carotid arteries? Subclavian?
R common carotid - brachiocephalic trunk
L common carotid - aorta
What arteries come off of the subclavian and at what landmarks do they change ?
Subclavian - axillary - brachial - deep brachial
Axilary starts at lateral border of 1st rib
Brachial starts at inferior border of trees major
What structures create the arterial anastomoses and what does this structure allow?
Network of arteries supply blood to back and shoulder
Dorsal scapular artery comes off subclavian, thoracodorsal artery, subscapular artery, posterior and anterior humeral circumflex
This structure allows blood to flow around the scapula into the scapular muscles even if one of the arteries is damaged, pinched or occluded this ensures that the muscles receive enough nutrients that the circulation is adequate
What is the parent structure of the circumflex scapular branch of subscapular artery
Subscapular artery
What does the subclavian vein break into?
Axillary (medial) and cephalic (lateral)
Axillary splits into brachial (lateral) and basilic (medial)
At the elbow (cubital fossa), the median cubital vein, which is a common site for venipuncture (drawing blood) connects cephalon and basilic
Shoulder flexion movers GHJ
Prime: anterior deltoid, coracobrachialis
Secondary: pec major, long head biceps
Horizontal abduction
Posterior delt, infraspinatus, trees minor, teres major
Horizontal Adductors
Pec major both heads
Secondary: anterior delt, coracobrachialis
What nerve can become impinged/entrapped at the top of the scapula? What ligament is involved?
Suprascalular nerve travels through supra scapular notch but NOT THE ARTERY
Nerve is held in place by superior transverse scapular ligament
Can occur because a thickened ligament
Common in athletes
Atrophy?
What are the three types of acromion and the associated condition?
Flat, Curved and Hooked
Hooked acromion due to bone spurs developed or you can be born with it
It can squeeze the contents of the subacromial space (tendons and ligaments) and cause subacromial impingement
What is the most commonly torn rotator cuff muscle?
Supraspinatus
What are the three ways a RCT can occur?
Articular Side - underside where it would mee the greater tubercle is torn
Bursal Side tear - Top side is torn
Full thickness tear
When is a Rotator Cuff Repair done?
If the edges of the tear can not be brought together, notch is creates in humerus just beneath articular surface to allow attachment of tendon through drill holes in bone using strong sutures
What is the glenoid labrum and what does it do
Fibrocartilage O ring that deepens a shallow socket (for the GHJ joint)
Connected to the long head of biceps = “stem” of the pear shaped labrum
What is a SLAP injury?
Superior Labrum anterior posterior
injured labrum
biceps pulls labrum off the bone
common in athletes
can begin as Long head of Biceps tendinitis and progress to SLAP
Scapulohumeral Rhythm SHR
Joint movements
coordinated movement between the scapulothoracic joint and the glenohumeral joint during arm elevation
STJ upwardly rotates, protracted and posterior tilts
GHJ externally rotates for greater tubercle to clear the acromion
Clavicle elevates and rotates backwards
SHR ratios
Early phase - initial 30 degrees of abduction is little to no ST motion
Mid phase (30-120) is 1:1 (so 90 degrees of motion, 45 is GHJ, 45 is STJ)
Late phase (120-180) is 2-3:1, so every 3 degrees GHJ, 1 degree STJ
The first 30 degrees of the ST ROM needs 30 degrees of clavicular elevation through A-P axis of SC joint
Second 30 degrees of ST ROM needs to have 50 degrees of clavicular rotation through longitudinal axis of clavicle at AC joint
What ligaments exist in the GHJ capsule and what movements do they limit
Coracohumeral - greatest stiffness
Glenohumeral ligament
Superior GHL limits inferior translation and ER
Middle GHL limits anterior translation
Inferior GHL is the hammock
Redundant capsule
At what angle is the GHJ capsule the tightest? What happens if the capsule is not tight?
90/90
Shoulder instability can result if the capsule is born loose or torn loose, becomes stretched out
How and where does Bursa emerge?
The synovial membrane protrudes through aperture in fibrous membrane to form bursa, exists between tendons and fibrous membrane
Subacromial or subdeltoid bursa
If this becomes inflamed in can take up more space
Sternoclavicular joint (type and degrees of freedom)
Synovial SADDLE
Head of clavicle with clavicular notch of manubrium
Contains a fibrocartilage disc
3 DF:
Elevation/depression
Protraction/retraction
Posterior/Anterior Rotation
SCJ ligaments
Anterior and posterior SC ligament - checks excessive A/P motion
Costoclavicular ligament - checks clavicular elevation and superior glide
Interclavicular ligament - checks excessive depression/downward glide
Use names and locations to remember movements
Acromioclavicular joint type and DF
Synovial plane joint
3 DF
weak joint capsule
Coracoid ligaments
Coracoacromial ligament
Acromioclavicular ligament
Coracoclavicular ligmanets:
- trapezoid more lateral guides during rotation
- conoid more medial prevents vertical displacement
Separated shoulder
can fall and have;
dislocation of acromioclavicular joint without ligament rupture
dislocation of acromioclavicular joint AND rupture of coracoclavicular ligament
Piano key
results from acromioclavicular injury where the clavicle pops up, you can push it back down but it will pop up again
instability of the ligament or injury
Bankart injury
damage to the labrum with anterior shoulder dislocation
Shoulder extension
Prime: posterior delt, lat, teres major
Secondary : pec major sternal head, long head triceps
Shoulder abduction
Middle deltoid and supraspinatus
Shoulder adduction
Lat, teres major, coracobrachialis, long head of triceps
Shoulder ER and IR
ER: infraspinatus and teres minor
IR: lat, teres major, subscapularis, pec minor
Shoulder ER and IR
ER: infraspinatus and teres minor
IR: lat, teres major, subscapularis, pec minor
