Pectoral Region, Shoulder Flashcards
Somite
- originate during 3rd week of embryogenesis
- day 20 = mesoderm differentiates
- after day 20 = differentiates into 44 pairs of somites (change into 31 sets of spinal nerves)
Somite Subdivisions
- sclerotome = bone and cartilage
- syndetome = (from sclerotome) tendon and ligament
- dermomyotome = dermatome and myotome (segmental innervation)
Formation of Limb Buds
- 4th week of development = upper limb buds appear as elevations of C5-T1
- cranial to caudal
- about a week later = lower limb buds appear as L2-S2 segments
Progression of Limb Buds
- distal limb buds flatten (palms/soles anterior + thumb/great toe cranial)
- flexures: limbs bend anteriorly, elbow/knee are directed laterally, palm/sole directed toward trunk
Torsion of Limb Buds
- end of 7th week
- proximal parts of upper and lower limbs undergo a 90 degree torsion in opposite directions
- elbow = caudal; knee = cranial
- in lower limb, permanent pronation (twisting) of leg so foot becomes oriented w/ great toe on medial side
Formation of Digits
- mesenchyme condenses into plates, forming cartilaginous models of future digital bones
- interdigital spaces sculpted by cellular apoptosis
Syndactyly
fusion of 2 or more digits
Polydactyly
extra digits, typically occurs bilaterally
Macrodactyly
enlarged digits
Adactyly
absence of digits
Ectrodactyly
“lobster-claw deformity”, typically missing middle digit, typically occurs 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
Synovial Joint
- distal ends of two bones articulate
- articular cartilalge
- capsule made of outer fibrous and inner synovial membrane
- fluid-filled … synovial fluid (lubrication)
Functional Joint
- no joint cavity
- held together by soft tissues
Joints of UE
- glenohumeral (GH)
- acromioclavicular (AC)
- sternoclavicular (SC)
- scapulothroacic (ST) = functional
What 3 muscles attach to the coracoid process?
coracobrachialis, short head of biceps brachii, pectoralis minor
What travels through the radial groove?
radial nerve, deep profunda brachial artery
Triarticulate
works across 3 joints
ex: triceps brachii (long head), biceps brachii
ABCS
aorta > brachiocephalic trunk > common carotid artery > subclavian artery
UE Vasculature
- subclavian a. > (1st rib) axillary a. > (teres major) brachial a.
- branches = suprascapular a., circumflex humeral a. (posterior + anterior), subscapular a., profunda brachii a.
Arterial Anastomoses
- all of the arteries are interconnected around the scapula
- can sprout new connections w/ each other that will bypass any blockages/occlusions
Shoulder Flexion
- prime movers = anterior deltoid, coracobrachialis
- secondary = pectoralis major (clavicular head), biceps brachii (long head)
Shoulder Extension
- prime movers = latissimus dorsi, teres major, posterior deltoid
- secondary = pectoralis major (sternal head), triceps brachii (long head)
Shoulder Abduction
middle deltoid, supraspinatus
Shoulder Adduction
latissimus dorsi, teres major, coracobrachialis, triceps brachii (long head)
Shoulder External Rotation
- prime movers = infraspinatus, teres minor
- secondary = posterior deltoid
Shoulder Internal Rotation
- prime movers = subscapularis, latissimus dorsi, teres major, pectoralis major
- secondary = anterior deltoid
Shoulder Horizontal Abduction
posterior deltoid, infraspinatus, teres minor, teres major
Shoulder Horizontal Adduction
- prime movers = pectoralis major
- secondary = anterior deltoid, coracobrachialis
Common Order of RC Tendon Injury
SITS
supraspinatus > infraspinatus > teres minor > subscapularis
Suprascapular Nerve Entrapment
- nerve travels through suprascapular notch
- thickened (superior transverse scapular) ligament can compress nerve
- muscles are weakened and can experience atrophy (supraspinatus, infraspinatus)
3 Types of Acromion
type I = flat
type II = curved
type III = hooked
Types of Rotator Cuff Tears (RCT)
- articular side = under-side, partial
- bursal side = top-side, partial
- full thickness = all the way through the tendon
Glenoid Labrum
- fibrocartilaginous “O” ring
- deepens shallow socket
- connected to long head of biceps brachii
SLAP Injury
- superior labrum anterior posterior
- “peel-back” … tendon of LHB pulls labrum off bone
Scapulohumeral Rhythm (SHR)
coordinated movement b/w ST joint and GH joint during arm elevation
- ST = upward rotation, protraction, posterior tilt
- GH = external rotation
- clavicle = elevation, rotation backwards
SHR
- total GH abduction = 180 degrees
- 2:1 ratio GHJ to STJ
- early phase = initial 30, little to no ST motion
- mid phase = 30 to 120, more 1:1
- late phase = 120 to 180, 2-3:1
GHJ Ligaments
- coracohumeral = greatest stiffness
- superior GHL = limits inferior translation + ER
- middle GHL = limits anterior translation
- inferior GHL = “hammock”
- tightest at 90/90
Shoulder Instability
- GH capsule is stretched out
- “born loose” = bilateral
- “torn loose” = unilateral
Bursa
- synovial membrane protrudes through aperture in fibrous membrane
- b/w tendons and fibrous membrane
- subdeltoid (subacromial), subscapular
Sternoclavicular (SC) Joint
- synovial saddle type
- head of clavicle articulates w/ clavicular notch
- fibrocartilage articular disc
- 3 degrees of freedom = elevation/depression, protraction/retraction, posterior/anterior rotation
SCJ Ligaments
- anterior + posterior SC ligament = limits excessive A/P motion
- costoclavicular ligament = limits clavicular elevation and superior glide
- interclavicular ligament = limits excessive depression/downward glide
Acromioclavicular (AC) Joint
- synovial plane
- 3 degrees of freedom
- weak joint capsule
- acromion is slightly inferior to distal clavicle
Coracoid Ligaments
- coracoacromial ligament = roof of subacromial space
- acromioclavicular ligament = stabilizes ACJ
- coracoclavicular (trapezoid) ligament = most lateral; guides clavicle during rotation
- coracoclavicular (conoid) ligament = triangular; prevents vertical displacement
Dislocation of ACJ
- “separated shoulder” = acromioclavicular ligament only
- “paino key” = both AC and two CC ligaments rupture
