locomotor system lesson 5 Flashcards by Ludovica guidi

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.

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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

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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)

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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)

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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

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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

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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

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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

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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

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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

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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

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INFRASPINATUS

origin: infraspinous fossa
insertion: middle facet of the greater tubercle of humerus
action: external rotation of the glenohumeral joint

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TERES MINOR

origin: lateral border of scapula
insertion: lower facet of the greater tubercle of the humerus
action: external rotation of the glenohumeral joint

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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

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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

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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

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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

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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

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final position of flexion and abduction

the position obtained by 180 degrees abduction can be obtained by 180 degrees flexion

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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.

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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