lecture 3- muscles that move the scapula Flashcards
what is the shoulder/ pectoral girdle?
features?
why do we care?
the shoulder girdle is the attachment point of the upper-limb to the axial skeleton
features: high mobility
why do we care? the shoulder girdle is a complex structure, efficient in the performance of many movements yet vulnerable to injury because of the many and varied stresses it encounters
joints/ articulations of the pectoral girdle 7
sternocostal
sternoclavicular
acromioclavicular
glenohumeral (shoulder joint)
costovertebral
Scapulothoracic
interclavicualr
joints
1acromioclavicular
2glenohumeral
3sternoclavicular
articulations
1vertebroclavicular
2vertbroscapular
3costoclavicular
joints
1.acromioclavicular
2.glenohumeral
3.sternoclavicular
4.sternocostal
articulations
1.vertebroclavicular
2.costoclavicular
3.costoscapular
sternoclavicular joint movement
synovial joint
movements:
-full elevation ~60 degrees
-anterior and posterior movement
-20-30 degrees occurs with protraction and retraction
-also allows for small amount of rotation
sternoclavicular joint: ligaments
interclavicular
-limits superior and lateral displacement of clavicle
costoclavicular
-main support limits all ROM except depression
sternoclavicular
-limits anterior and posterior glide of clavicle
acromioclavicular joint: movements
synovial place joint
serves as restriction to overhead movements
the motions of AC joint are described as scapular movement with respect to the clavicle
-upward/downward rotation at an axis directed perpendicular to the scapular plane facing interiorly and medially
-int and external rotation about an approximate vertical axis
-anterior/ posterior tripping or tilting about an axis directed laterally and anteriorly
acromioclavicular joint: ligaments
coracolavicular ligament
-conoid
-trapezoid
acromioclavicular ligament
-prevents separation of clavicle and scapula
-prevents posterior and anterior displacement
coracoacromical ligament
-forms roof over glenohumeral joint
-protection for bursa and suprapinatus tendon
-provides limit to superior humeral head
Scapulothoracic joint: scapula
physiologic articulation between the rib cage and the scapula
scapularthoacic joint: movements
physiology joint (not a typical articulation of bone to bone)
contains muscular and bursal structures to allow smooth movement
function- allows arm to abduct beyond the 120degree allowed by the glenohumeral joint alone (1 degree of scapular rotation for every 2 degrees of humeral abduction)
-movement in three directions
protraction & retraction (30-60)
superior & inferior rotation (60)
elevation &depression (30)
pectoral gridle: layout and movement
arm in anatomical position:
clavicle is 20-30 degrees posterior to frontal plane
scapula is oriented 35 degrees anterior to the frontal plane
protraction and retraction of the scapula
protraction:
-serratus anterior
-pectoralis major
-pectoralis minor
retraction:
-trapezius (middle part)
-rhomboids
serratus anterior: origin, insertion, action
origin: external surfaces of the lateral parts of ribs 1-8
insertion: anterior surfaces of the medial border of the scapula
action: Protracts the scapula and
holds it against the
thoracic wall; rotates the
scapula in an upward
direction
pectoralis major
Origin - Clavicular Head: Anterior surface of the medial half of the clavicle
Sternocostal head: anterior surface of the sternum, superior six costal cartlidges , aponeurosis of the
external oblique muscle.
Insertion - Lateral lip of the intertubercular groove
of the humerus .
Actions - Adducts and medially rotates the humerus; draws the scapula anteriorly and inferiorly. Acting alone the clavicular head flexes the humerus, and the sternocostal head will extend the humerus from a flexed position
pectoralis minor
origin-ant. surface of ribs 3,4, &5
insertion- coracoid process of the scapula
action- anchors, depresses and protracts the scapula
Middle Fibers of Trapezius
Origin: Spinous processes of the first-
fifth thoracic vertebrae.
* Insertion: Medial margin of the
acromion and superior lip of the spine of the scapula.
* Action: Retracts the scapula
* Innervation: Spinal Accessory
Nerves (CN XI)
rhomboids major
origin: spinous processes of the thoracic vertebrae 2-5
insertion: by fibrous attachment to the medial border of the scapula between the spine and inferior angle
action: adducts and elevates the scapula
what muscles elevate the scapula
levator scapula
trapezius
rhomboids
upper fibers of the trapezius
Origin: External occipital
protuberance, medial 1/3 of the
superior nuchal line, ligamentum
nuchae and spinous process of the 7th
cervical vertebrae.
* Insertion: Lateral 1/3 of the of the
clavicle and acromion process of the
scapula.
* Action: Elevates the scapula
* Innervation: Spinal Accessory
Nerves (CN XI)
levator scapula
Origin:
– Transverse processes of the first 4
cervical vertebrae.
* Insertion:
– Medial border of the scapula,
between the superior angle and the
root of the spine.
* Action:
– Elevates scapula and assists with
downward rotation of the scapula.
– Can also assist with lateral flexion of the c-spine (unilaterally) or extension of the c-spine (bilaterally), if the scapula is stabilized by other
muscles.
* Innervation:
– Cervical 3 & 4, and Dorsal Scapular
nerve (C4, C5)
Levator Scapulae
what muscles would cause depression of the scapula
lower trapezius
subclavius
pectoralis minor
gravity
lower trapezius
Origin: Spinous processes of the 6th-12th thoracic vertebrae.
* Insertion: Tubercle at the apex of the spine of the scapula.
Action: Depresses the scapula and
retracts scapula
* Innervation: Spinal Accessory
Nerves (CN XI)
subclavius
Origin – Junction of 1st rib and its costal cartlidge
Insertion – Inferior surface of the middle third of the clavicle
Action – Anchors and depresses the scapula Innervation – Nerve to subclavius (C5, C6)
what muscles rotate the scapula upward/downward?
upward: trapezius upper and lower fibers
serratus anterior
downward:
levator scapulae
rhomboids
pectoralis minor
gravity
rhomboids minor
origin: ligamentous nuchal, spinous process of the 7th cervicle and 1st thoracic vertebrae
insertion: medial border of the scapula, at the root of the spine of the scapula
action: adducts and elevates scapula
