Pectoral Girdle and Shoulder SDL Flashcards
Describe the lateral 1/3 of the clavicle
Concave
Describe the medial 2/3 of the clavicle
Convex
What does the lateral end of the clavicle articulate with?
Acromion –> AC join
What does the medial end of the clavicle articulate with?
Manubrium of sternum and first costal cartilage –> sternoclavicular joint
How do clavicular fractures usually occur?
Usually occur by a direct blow to the shoulder e.g. during a fall or a car collision
Which part of the clavicle usually fractures?
The middle portion (shaft) of the bone
Where does the scapula lie?
Lies on the back of the rib cage between the second and seventh ribs
Where does the scapula articulate with the humerus?
At the glenoid fossa to form the shoulder (glenohumeral) joint
What is the dorsal surface of the scapula divided into?
Supraspinous and infraspinous by the spine of the scapula
What holds the scapula and clavicle together?
Extremely strong ligaments
What are the movements of the scapula?
• up and down (elevation and depression) • forwards (protraction = reaching the arm out in front, as if to push open a door, or throw a punch) • backwards (retraction = ‘squaring’ the shoulders) over the chest wall.
How does the scapula move so the arm can be lifted above the head?
The scapula can move so that the inferior angle can be moved laterally and cranially from the anatomical position. This movement brings the face of the glenoid cavity upwards and allows the arm to be lifted above the head
Where are muscles the move the scapula attached to?
The pectoral girdle, trunk, head and neck
What are the 2 groups of muscles that move the pectoral girdle?
- Dorsal (posterior) group 2. Ventral (anterior) group
What is the dorsal group of muscles comprised of?
2 superficial muscles and 3 deep muscles Superficial: trapezius, lat dorsi Deep: rhomboid major, rhomboid minor, levator scapulae
Diagram of humerus
Palpating scapula on person
Label the muscles
- Trapezius
- Lat dorsi
- Rhom minor
- Rhom major
Origin and insertion of the trapezius?
Origin:
- Superior fibres: superior nuchal line, external occipital protuberence (lower part of skull)
- Middle fibres: nuchal ligament, spinous processes of C1-C6 and C7-T3
- Inferior fibres: spinous processes of T4-T12
Insertion:
- Superior fibres: clavicle
- Middle fibres: acromion and spine of scapula
- Inferior fibres: spine of scapula
What is the trapezius innervated by?
Is the only muscle of the upper limb that does not receive its innervation from the brachial plexus.
Motor: accessory nerve (CN XI)
Sensory: ventral rami C3-C4
Movements on scapula of upper fibres alone of trapezius?
Elevates scapula
Movements alone of middle fibres of trapezius on scapula?
Retracts scapula
Movements alone of inferior fibres of trapezius on scapula?
Depresses scapula
Movement on scapula of all fibres of trapezius working together?
Head and neck extension
Where is lat dorsi located?
Sweeps over the lumbar region and lower thorax and converges to a narrow tendon that inserts on the anterior surface of the humerus. Contribues to the posterior wall of the axilla.
Where does the lat dorsi insert?
Inserts on the floor of the intertubercular groove of the humerus
What are the origins of the lat dorsi?
Vertebral part: Spinous process of T7-L5 and the thoracolumbar fascia.
Costal part: origins from the 9th to 12th ribs
Iliac part: iliac crest
Actions of the lat dorsi?
- Extends arm
- Adducts arm
- Medially rotates arm
Innervation of lat dorsi?
Thoracodorsal nerve (C6-C8)
What are the 3 deep dorsal muscles of the pectoral girdle?
- Levator scapulae
- Rhomboid major
- Rhomboid minor
Origin and insertion of levator scapulae?
Origin: transverse processes of C1-C4 (neck)
Inserts: Upper portion of medial border of scapula
Action of levator scapulae?
Elevates scapula towards neck
Origin and insertion of rhomboid major?
Origin: spinous processes of T2-T5
Inserts: Attaches to the medial border of the scapula, between the scapula spine and inferior angle.
Action of rhomboid major?
Retracts and rotates the scapula.
Innervation of levator scapulae?
Dorsal scapular nerve
Innervation of rhomboid major?
Dorsal scapular nerve.
Origin and insertion of rhomboid minor?
Origin: spinous processes of C7-T1 vertebrae
Insertion: Attaches to the medial border of the scapula, at the level of the spine of scapula
Action of rhomboid minor?
Retracts and rotates the scapula.
Innervation of rhomboid minor?
Dorsal scapular nerve.
What muscles are part of the ventral aspect of the pectoral girdle?
- Serratus anterior
- Pec major
- Pec minor
Origin and insertion of pec major?
Origin:
- Sternal part: from anterior surface of sternum, from costal cartilages 1-6/7
- Clavicular part: from anterior surface of medial clavicle
Inserts:
- Lateral lip of intertubercular sulcus of the humerus
Action of pec major?
Adducts upper limb –> fibres contract and pull humerus towards body
Medially rotates the upper limb and draws the scapula anteroinferiorly.
The clavicular head also acts individually to flex the upper limb –> clavicular fibres contract and pull humerus upwards
Innervation of pec major?
Lateral and medial pectoral nerves.
Origin and insertion of serratus anterior?
Origin: Lateral aspects of ribs 1-8/9
Inserts: They attach to the costal surface of the medial border of the scapula.
Actions of serratus anterior?
Protraction and rotation of scapula
Innervation of serratus anterior?
Long thoracic nerve
Origin and insertion of pec minor?
Origin: Ribs 3-5
Inserts: coracoid process of scapula
Action of pec minor?
It stabilises the scapula and contributes to protraction of the scapula.
Innervation of pec minor
Medial pectoral nerve.
What movements are possible at the shoulder joint?
Flexion, extension, abduction, adduction, circumflexion, medial /lateral rotation
What are the ‘scapulahumeral’ muscles?
They pass from the scapula and insert onto the humerus. They act upon and stabilise the shoulder.
- Deltoid
- Teres major
- Rotator cuff muscles
Origin and insertion of deltoid?
Origin: Lateral third of the clavicle, the acromion and the spine of the scapula
Inserts: It attaches to the deltoid tuberosity on the lateral aspect of the humerus.
Innervation of deltoid?
Axillary nerve
Diagram of where deltoid inserts
What movements does deltoid participate in?
Anterior fibres – flexion and medial rotation.
Posterior fibres – extension and lateral rotation.
Middle fibres – the major abductor of the arm (takes over from the supraspinatus)
Origin and insertion of teres major?
Origin: Posterior surface of the inferior angle of the scapula
Insertion: medial lip of the intertubercular groove of the humerus.
Innervation of teres major?
Lower subscapular nerve.
Action of teres major?
Adducts and extends at the shoulder, and medially rotates the arm.
What are the 4 rotator cuff muscles?
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Which is only muscle of the four located on the anterior aspect of the scapula?
Subscapularis
origin and insertion of supraspinatus?
Origin: posterior aspect of scapula, above spine (supraspinous fossa)
Inserts: attaches to greater tubercle of humerus
Action of supraspinatus?
Begins abduction (first 20 degrees)
Then assists deltoid after 20 degrees
Origin and insertion of infraspinatus?
Origin: infraspinous fossa on posterior scapula
Inserts: greater tubercle on humerus
Action of infraspinatus?
Laterally rotates the arm.
Innervation of supraspinatus?
Suprascapular nerve.
Innervation of infraspinatus?
Suprascapular nerve.
Origin and insertion of teres minor?
Origin: posterior surface of the scapula, adjacent to its lateral border.
Insertion: greater tubercle on humerus
Action of teres minor?
Laterally rotates the arm (same as infraspinatus)
Innervation of teres minor?
Axillary nerve
Origin and insertion of subscapularis?
Origin: subscapular fossa (anterior surface of scapula)
Inserts: lesser tubercle on humerus
Innervation of subscapularis?
Upper and lower subscapular nerves.
Action of subscapularis?
Medially rotates arm
Is this a right or a left scapula?
Right
Is this a right or left humerus? Is it the posterior or anterior surface?
Right humerus, posterior surface
- Posterior surface of the humerus: can see the olecranon fossa and cannot see the lesser tubercle (an anterior bony landmark).
- Right humerus: the humeral head must lie medially because it articulates with the glenoid fossa, meaning this is a right humerus.
What muscle is indicated by the letter A
Pec major
Muscle A is innervated by which nerve?
Long thoracic nerve
What is muscle B? What is its movement? Where does it insert?
Infraspinatus
Movement: lateral rotator of shoulder
Inserts: greater tubercle of humerus
Label muscle C
Teres minor
Label the bony landmarks
A - lesser tubercle
B - greater tubercle
C - head of humerus
D - surgical neck
E - deltoid tuberosity
The muscle labelled A primarily acts upon the shoulder in which way?
Abductor (although the anterior fibres contribute to flexion and the posterior fibres to extension)
What muscle attaches to each of the labelled regions?
A - levator scapulae
B - rhomboid minor
C - supraspinatus
D - rhomboid major
E - infraspinatus
F - teres minor
G - teres major
What muscle originates from the posterior surface of the inferior angle of the scapula?
Teres major
What muscle attaches to the medial border of the scapula, at the level of the spine of scapula?
Rhomboid minor
What muscle attaches to the medial border of the scapula, between the scapula spine and inferior angle?
Rhomboid major
What is this muscle? Where does it originate? Where does it insert? What is its movements?
Trapezius
Origin: occiput, nuchal ligament in the neck and the thoracic vertebrae
Inserts: on the clavicle and spine of the scapula
Movements: Its upper, middle and inferior fibres are orientated in different directions, meaning that these segments of fibres move the scapula differently if they are working independently: the upper elevate (shrugging the shoulders), the middle retract and the inferior depress, the scapula.
Onto which bony landmark does muscle A insert?
Pec minor inserts onto coracoid process of scapula
What muscle inserts onto E? How can this muscle act upon the shoulder?
Deltoid (deltoid tuberosity shown here)
Abduct, flex, extend shoulder via its middle, anterior and posertior fibres respectively
What nerve innervates muscle C?
Axillary nerve (teres minor shown here)
What muscles are A and B? Contraction of the muscles indicated by the letters A and B results in what movement of the scapula?
A - rhomboid major
B - rhomboid minor
When they contract they pull the medial border of the scapula back towards the vertebrae; retraction.
Deltoid originates from which region(s) of the scapula?
A (acromion)
B (spine of scapula)
Identify the muscle indicated by the letter A.
Lat dorsi
How does contraction of serratus anterior move the scapula?
Protraction
Movements of muscle A?
Pec minor
- Protraction of shoulder
- Stabiliser of scapula
Identify muscle A
Subscapularis
This image shows the anterior aspect of the pectoral girdle and shoulder - we can work this out because if it was the posterior aspect we would be able to see the spine of the scapula and more than one muscle over the scapula; here we see just one. This muscle originates on the anterior surface of the scapula and inserts onto the humerus.
When is the axillary nerve at risk of being damaged?
- Humeral surgical neck fracture (the axillary nerve runs close to the surgical neck of the humerus)
- Anterior shoulder dislocation (the dislocated humeral head may stretch the nerve)
What inserts on the a) medial b) lateral c) floor of the intertubercular sulcus of the humerus?
a) medial –> teres major
b) lateral –> pec major
c) floor –> lat dorsi
Name muscle C. Where does it insert? What is its movements?
Teres major
Inserts onto medial aspect of intertubercular sulcus
Adductor and medial rotator of shoulder joint (due to origin from posterior surface of inferior angle of scapula to the medial lip of the intertubercular sulcus)
The examiner is assessing the function and power of which muscle?
Subscapularis (medial rotation)
Label muscle B and C
B - teres minor
C - teres major
Label muscle A. What is its movements?
Supraspinatus
- Stabilises shoulder
- Initiates abduction of shoulder
What is E?
Infraglenoid tubercle
Identify muscle A
Subscapularis
Name the letters
A - Acromioclavicular joint
B - Acromion
C - Coracoid process
D - Medial border of scapula
E - Glenoid fossa
F - Lateral border of scapula
G - Head of humerus
H - Greater tubercle
The muscle that lies in the region indicated by the letter A? What is its movements?
This bony landmark / region is the supraspinous fossa –> supraspinatus lies here and is an abductor of the shoulder joint
Name the muscles. Which of these are borders of the quadrilateral space?
A - infraspinatus
B - teres minor
C - teres major
D - long head of triceps
Teres minor, teres major, long head of triceps comprise 3 of the 4 borders of the quadrilateral space.
What is the labelled muscle? What is its origin and insertion? Movements?
This is the anterior surface of the scapula and the muscle is subscapularis.
Origin: subscapular fossa
Inserts: lesser tubercle on humerus
Medially rotates shoulder
What does the dorsal scapular nerve innervate?
Rhomboid major, rhomboid minor, levator scapulae
Why are those who dislocate their shoulders often more prone to future dislocations?
When humeral head moves anteriorly and medially, it can stretch/tear the glenoid labrum so cannot help with stability of shoulder joint anymore
How does biceps tendon add to stability of shoulder joint?
One of the tendons of biceps runs in the biciptal groove / intertubercular sulcus, runs through the shoulder joint and inserts on the supraglenoid tubercle
This adds stability as tendon runs through joint
