Lecture 3 & 4 - Pectoral Girdle and Scapular Control Flashcards
what is the shoulder/pectoral girdle?
the attachment point of the upper limb to the axial skeleton
- > it has high mobility and therefore lower stability
parts of the sternum
Upper Portion
- > manubrium
Mid Portion
- > body
Lower portion
- > xiphoid process
Joints/Articulations of the pectoral girdle
- Sternocostal
- Sternoclavicular
- Acromioclavicular
- Glenohumeral (Shoulder joint)
- Costovertebral
- (Scapulothorasic) articulation
- (interclavicular) articulation
movement of sternoclavicular joint
- > synovial saddle joint
- > Movement
* full elevation is around 60 deg
*ant/post, protraction/retraction and small amounts of rotational movement
ligaments of the sternoclavicular joint and how they each limit motion
- Interclavicular ligament
- > limits sup and lateral displacement of clavicle - Sternoclavicular ligament
- > limits ant and post gliding of clavicle - Costoclavicular ligament
- > main support limits all ROM except depression
Parts of the clavicle
movements of the acromioclavicular joint and what’s its main function
synovial plane joint, gliding motions
- > serves as a restriction too over-head arm movements; scapular movements with respect to the clavicle
- > up/downward in/external rotation
- > ant/posterior tilting or tipping
ligaments of the acromioclavicular joint and how they limit motion
Coracoclavicular ligament
- > conoid and trapezoid
- > primary retraint to vertical displacement
Acromioclavicular lig
- > prevents separation of clavicle and scapula, and posterior displacement
Coracoacromial lig
- > forms roof over glenohumeral joint
- > provides limit to superior humeral head movement
- > protects bursa and supraspinatus tendons
scapulothoracic joint movements
- > physiological joint
movm’t in three directions
- pro/retraction (also known as add/abduction)
- sup/inf rotation (also known as up/downwards rot)
- elevation/depression
function of scapulothoracic joint and explain scapulo-humeral rhythm
allows arm to abduct beyond the 120deg allowed by the glenohumeral joint alone
Scapulo-humeral rhythm
- > 1deg of scapular rotation for ever 2deg of humeral abduction
layout of the structures of the pectoral girdle in anatomical position
- > clavicle is 20deg posterior to frontal plane
- > scapula is oriented 35 degrees anterior to the frontal plane
primary muscles involved with protraction and retraction of the scapula
Protraction
- > serratus anterior (also holds scapula against thoracic wall)
- > pectoralis major and minor
Retraction
- > trapezius (middle part)
- > rhomboids
origin and insertion points of the serratus anterior
Origin
- > external surfaces of the lateral parts of ribs 1-8 (ser(8)tus)
Insertion
- > anterior surface of the medial border of the scapula
actions of the serratus anterior and what innervates this muscle
- > it protracts the scapula and hold it against the thoracic wall
- > rotates the scapula in an upwards direction
- > it is innervated by the long thoracic nerve
origin and insertion of pectoralis major
Origin
- > clavicular head: anterior surface of the medial half of the clavicle
- > sternocostal head: anterior surface of the sternum
Insertion
- > lateral lip of the intertubuercular/bicepital groove of the humerus
actions of pectoralis major and how its innervated
- > adducts and medially rotates the humerus
- > draws the scapula anteriorly and inferiorly
- > innervated by the lateral and medial pectoral nerves
origin and insertion, actions of pectoralis minor and how its innervated
Origin
- > anterior surface of ribs 3,4,5
Insertion
- > coracoid process of the scapula
Action
- > anchors and depresses the scapula
Innervated by medial pectoral nerve
insertion and origin, action, and innervation of middle trapezius
origin
- > spinous processes of T1-5
insertion
- > medial margin of the acromion and superior lip of the spine of the scapula
action
- > retracts the scapula
innervation
- > spinal accessory nerves (Cranial Nerve 11)
insertion and origin, action, and innervation of upper fibres of trapezius
Origin
- > external occipital protuberance, medial ⅓ of the superior nuchal line, ligamentum nuchae and spinous process C7
insertion
- > lateral ⅓ of the clavicle and acromion process of the scapula
action
- > elevates the scapula
Innervation
- > spinal accessory nerves
Origin and insertion, action, and innervation of lower fibres of trapezius
origin
- > spinous process of T6-12
insertion
- > tubercle at the apex of spine of the scapula
action
- > depresses the scapula and retracts scapula
innervation
- > spinal accessory nerves
rhomboids
origin
- > ligamentus nuchae, spinous process of C7 and T1 (minor)
- > spinous processes of T2-5 (major)
insertion
- > medial border of the scapula between the pine and inferior angle (major)
- > medial border of the scapula, at the root of the spine of scapula (minor)
action
- > adducts and elevates the scapula
innervated
- > dorsal scapular nerve
what actions are possible with the pectoral girdle
which muscles would elevate the scapula
- > levator scapulae
- > trapezius
- > rhomboids
origin/insertion, action and innervation of levator scapulae
origin
- > transverse processes of C1-4
insertion
- > medial border of scapula, between sup angle and root of spine
action
- > elevates scapula and assists with downward rotation
innervation
cervical nerves 3 and 4, dorsal scapular nerve
which muscles depress the scapula
- > trapezius (lower part)
- > subclavius
- > gravity
which muscles rotate the scapula
Upward rotation
- > trapezius (upper and lower fibres)
- > serratus anterior
Downward rotation
- > levator scapulae
- > rhomboids
- > pectoralis minor
- > gravity
types of joint lever systems
F=fulcrum
E=effort
L=load
- > first class like a seesaw
how does changing the position of the fulcrum in a first class lever change E and L
how do we have a force disadvantage but a movement advantage with 3rd class levers
*distance from E-F and E-L*
2nd class lever
L is in the middle
- > force advantage since there is less force needed as the load is more dispersed but movement disadvantage since we can’t move that much
skeletal muscle fiber organization
- > circular (mouth)
- > parallel
- > convergent (like a fan)
- > pennate
- unipennate
- bipennate
- multipennate
actions of skeletal muscles
Agonist (prime mover)
- > produces a specific movement when it contracts (bicep)
Antagonist
- > a muscle whose action opposes/reverses that of an agonist (tricep)
Synergist
- > a muscle that assists the agonist or prime mover
types of muscle contraction
things that can cause shoulder pain
- > scapular control
- musculature weakness and imbalance
- innervation
- > rotator cuff musculature
- weakness and imbalance
- innervation
- tendinopathy (rubbing/irritation of tendon)
- > instability
- glenoid labrum injury
- dislocation and sublaxation
define scapular control and what is poor scapular control
the combined movement of humerus and scapular (scapulohumal rhythm)
- > for every 2 deg shoulder abduction, theres 1dec of upward scapular rotation
poor scapular control when performing arm movements is caused by inadequate movement of the scapula
nerves involved in scapular control
Long thoracic nerve
- > innervates serratus anterior
- > damage from blunt force trauma of lower armpit can cause paralysis of this muscle
Suprascapular nerve
suprascapular nerve entrapment
- > nerve passes through suprascapular notch so swollen supraspinatus can entrap it
- > most commonly caused by extremes of scapular motions associated with throwing actions
- which causes localized pain and muscle weakness
