locomotor system lesson 5 Flashcards
which ligament is the main stabilizer of the abducted shoulder (in extreme abduction)?
the inferior glenohumeral ligament. When we have our arm raised upwards (extreme abduction) the ligament protects the joint by limiting movement.
tendon of the long head of the biceps brachii
-ORIGIN: supraglenoid tubercle of scapula
it is partially fused in the superior margin of the glenoid labrum and it passes inside the intertubercular groove.
-insertion: radial tuberosity of radius (acts also on the elbow)
-It is protected by the transverse humeral ligament.
-the main function of this tendon is to stabilize the head of the humerus within the glenoid cavity, to prevent the superior dislocation
-it is essential also for the abduction of the glenohumeral joint: it presses the humeral head against the glenoid cavity
-main supinator and flexor of the elbow
short head of the biceps
originates from the coracoid process
it is a stabilizer for the head of the humerus as well, it prevents its downward dislocation
due to its upward pull on the humeral head.
insertion: radial tuberosity of radius (is also the main flexor and the main supinator of the elbow)
3 groups of muscles at the level of the proximal upper limb
-muscles connecting the shoulder girdle to the trunk
-muscle connecting the scapula to the humerus
-muscle connecting the trunk to the humerus (with no or little attachment to the scapula)
SERRATUS ANTERIOR
-connects the trunk to the shoulder girdle
-important to define the scapulo thoracic false joint
-origin: anterolateral aspect of the thorax, from the first to the 9th rib
insertion: in the anteromedial border of the scapula
action: abduction and upwards rotation of the scapula
TRAPEZIUS
-connect the cervical spine, the thoracic spine and the skull to the clavicle, the scapula and the acromion
-origin: from the occipital bone and from the spinous processes of the vertebral bodies (from C7 to T12)
-insertion: spine of the scapula, acromion and acromial end of the clavicle
-actions
1)upper trapezius: acts on the skull and on the cervical spine providing extension of the neck, lateral flexion and contralateral rotation. We have lateral flexion and contralateral rotation only if half the trapezius is contracted, if both parts are contracted we have extension of the neck
2)lower trapezius: adduction, depression and upwards rotation of the scapula
3) middle trapezius:helps the lower trapezius with the adduction and the upwards rotation of the scapula
upper part: works on the neck
lower part: works on the scapula
RHOMBOID MAJOR AND MINOR
origin: from the ligamentum nuchae and
from the last 2 cervical vertebras (the minor)
-then the major from the upper 4 thoracic vertebrae
insertion: medial boarder of the scapula
action: adduction, downwards rotation and elevation of the scapula
PECTORALIS MINOR
origin: from the 3rd to the 5th ribs
insertion: coracoid process of the scapula
action: elevation of ribs from 3 to 5 (abduction), depression of the scapula
LEVATOR SCAPULAE
origin: lateral processes of the upper cervical vertebrae
insertion: upper medial border of the scapula, at the level of the superior angle of the scapula
action: elevation and downwards rotation of the scapula, lateral flexion and ipsilateral rotation of the cervical spine
DELTOID MUSCLE
origin: acromial end of the clavicle, acromion and the spine of the scapula
insertion: deltoid tuberosity of the humerus
action
main function–>abduction of the glenohumeral joint
anterior and middle part of deltoid–> allow flexion and horizontal abduction of the glenohumeral joint
posterior part–>allows the extension and horizontal abduction of the glenohumeral joint
SUPRASPINATUS
origin: supraspinous fossa
insertion:uppermost facet of the greater tubercle of the humerus
action:abduction of the glenohumeral joint in the smallest degrees of action (0-60*)
main stabilizer of the glenohumeral joint: it keeps down the head of the humerus preventing superior dislocation
INFRASPINATUS
origin: infraspinous fossa
insertion: middle facet of the greater tubercle of humerus
action: external rotation of the glenohumeral joint
TERES MINOR
origin: lateral border of scapula
insertion: lower facet of the greater tubercle of the humerus
action: external rotation of the glenohumeral joint
SUBSCAPULARIS
origin: sub scapular fossa
insertion: lesser tubercle of the humerus
action: internal rotation of the glenohumeral joint
depending on the position of the arm it can provide flexion, extension and abduction of the glenohumeral joint
TERES MAJOR
origin: inferior angle of the scapula
insertion: the crest of the lesser tubercle of the humerus
action: internal rotation, adduction and extension of the glenohumeral joint
PECTORALIS MAJOR
origin: from the clavicle (sternal half), sternum, costal cartilages of the second to seventh ribs and the aponeurosis over the abdominal muscles
insertion: the crest of the greater tubercle of the humerus (on an area 7 inches long)
action
-adduction and internal rotation of the glenohumeral joint
-the clavicular heads allow flexion of the glenohumeral joint
LATISSIMUS DORSI
origin: all the spinous processes from T6 to the sacrum, crest of the ilium and the lowest ribs
insertion: to the crest of the lesser tubercle of the humerus (proximal to the teres major but more distal)
action:
internal rotation, extension and adduction of the glenohumeral joint
scapular depression, although it doesn’t insert into the scapula directly but it helps because it is very big
abduction, degrees and joint involved
from 0-60, glenohumeral joint
from 60-120 also the scapulothoracic joint is involved
from 120-180 involves movement of the glenohumeral joint, the scapulothoracic joint and the flexion of the trunk on the opposite side
final position of flexion and abduction
the position obtained by 180 degrees abduction can be obtained by 180 degrees flexion
deltoid in abduction
can reach a full range of abduction by itself
at 90 degrees it reaches its maximal efficiency
At 90 degrees of abduction (when the arm is horizontal, parallel to the ground), the deltoid muscle reaches its peak efficiency. This position maximizes the muscle’s leverage, allowing it to generate the most force. The muscle fibers are optimally aligned to lift the arm against gravity with less effort, compared to other positions.