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.
role of the supraspinatus
it protects the humeral head from superior dislocation by stabilizing it at the glenoid cavity.
it helps the deltoid in abduction–>without the supraspinatus the deltoid could still perform abduction but it would need more energy.
the other rotator cuff muscles play a vital role in the deltoid-supraspinatus synergism and are essential for the action of the deltoid. They stabilize the humeral head to the glenoid cavity, preventing superior and lateral dislocations of the humeral head
phases of abduction
0-90, the muscles involved are the deltoid and the supraspinatus
from 90-150, the scapula has to rotate anti clockwise such that the glenoid cavity faces superiorly and adheres with the humeral head
150-180, to allow the hand to reach the vertical position the contralateral spine needs to flex a little bit
reference position for rotation
the elbow should be flexed at 90 degrees with the forearm lying within a sagittal plane
external rotation degrees max
bring the palmar side of the hand away from the thorax
max 80 degrees
internal rotation degrees max
bring the palmar side of the hand close to the thorax
100-110
circumnduction
combines the elementary movements about the 3 cardinal axes
CORACOBRACHIALIS MUSCLE
origin: coracoid process (same as short head of biceps brachii)
insertion: diaphysis of the humerus
action: helps in the flexion of the glenohumeral joint (not involved in elbow due to the insertion)
NB: IN ANTERIOR PART OF THE ARM
BRACHIALIS MUSCLE
origin: middle part of the diaphysis of the humerus
insertion: anterior tuberosity of the ulna
action: helps in the flexion of the elbow
NB: IN ANTERIOR PART OF THE ARM
TRICEPS
long head
origin: inferior tubercle of the glenoid cavity
lateral head
origin: posterior proximal part of the humerus
middle head
origin: posterior proximal part of the humerus, placed more deeply
insertion: all three bellies converge in one single tendon that inserts on the olecranon process of the ulna
action: extension of the elbow
the long belly helps also on the extension of the glenohumeral joint
elbow
represents the mechanical link between the upper arm and the forearm.
3 bones involved in the elbow joint
distal epiphysis of the humerus, proximal epiphysis of the radius and proximal epiphysis of the ulna
distal epiphysis of humerus divided in
-medial condyle
-lateral condyle
at each condyle we have a single bone tuberosity
-medial epicondyle
-lateral epicondyle
on the lateral condyle we have
-capitellum, that articulates with the proximal epiphysis of the radius
-radial fossa, placed superiorly to the capitellum and accepts the proximal radius during complete flexion of the elbow
on the medial condyle we have
-trochlea: articulates with the proximal epiphysis of the ulna
-coronoid fossa: accepts the coronoid process of the ulna during maximal flexion and is placed superiorly to the trochlea
the proximal radius is composed of
-head: concave, that accepts the convexity of the capitellum
-neck
-radial tuberosity, insertion of the biceps brachii
the proximal ulna is composed of
anterior process: coronoid process
posterior process: olecranon process (insertion of triceps tendon)
during flexion and extension the ulna slides over the trochlea of the humerus distal epiphysis
the elbow has only one joint cavity but it comprises 3 joints
-between the ulna and the radius
-between the radius and the humerus
-between the ulna and the humerus
radial collateral ligament or lateral collateral ligament
-stabilizes the one joint capsule surrounding the radius, the ulna and the humerus
-it originates from the lateral epicondyle and it connects it to the proximal radius
composed of
-anterior fibers
-intermediate fibers
-posterior fibers
ulnar collateral ligament or medial collateral ligament
stabilizes the elbow joint
originates from the medial epicondyle and it connects it to the proximal ulna
composed of:
-anterior fibers
-posterior fibers
-coopers ligament (or transverse ligament)
annular ligament of the radius
stabilizes the superior radius ulnar joint (between the radius and the ulna)
is partially fused with the lateral collateral ligament
transverse ligament
partially fused with the medial collateral ligament
what does the coronoid fossa receives during flexion?
coronoid process of the ulna
what does the olecranon fossa receives during extension?
the olecranon process of the ulna
movements of the elbow joint
flexion-extension thanks to the main elbow joint
pronation-supination thanks to the ulnar radius joint and the annular ligament
the trochlear notch of the ulna ends anteriorly and posteriorly with?
anteriorly with the coronoid process
posteriorly with the olecranon process
trochlear notch
part of the ulna
trochlear groove
part of the trochlea on the humerus
BRACHIORADIALIS MUSCLE
origin: lateral condyle of the distal epiphysis of the humerus
insertion: styloid process of radius
action: flexion of the elbow
provides complete supination if we are in a complete pronation
complete pronation if we are in a complete supination
flexor muscles
biceps brachii
brachialis muscle
brachioradialis
they work at their best advantage when the elbow is flexed at 90 degrees
active flexion
range of 145 degrees
we have the contraction of muscles that occupy more space
passive flexion
reaches 160 degrees
no muscle activation
the relaxed muscles can be flatten against eachother allowing passive flexion
