20-01-22 - Pectoral and Scapular Regions Flashcards
Learning outcomes
- Describe the movements of the pectoral girdle, the muscles and their features (i.e. attachments, innervation, actions)
- Describe the movements of the Glenohumeral joint, the muscles and their features
- Explain the importance of scapular rotation
- Describe the “gateways” and their contents in the scapular region
- Describe the significance of the Rotator cuff
What are the 4 muscles in the anterior chest?
What do they each move?
What are they innervated by?
Muscles in the anterior chest:
1) Subclavius
• Moves the clavicle
• Innervated by Nerve to Subclavius – roots C5, C6
• Origin is at the first 1st costal cartilage
• Inserts into the lower border of the clavicle
• Stabilises/depresses the clavicle
2) Pectoralis major
• Moves the humerus
• Innervated by the Median (C8 and T1) and Lateral Pectoral (C5, C6, C7) nerves
• 2 heads
• Clavicular head attaches to medial third of clavicle
• Sternocostal head attaches to upper 6 ribs
• Both heads come down and converge on the lateral lip of the intertubercular sulcus of the humerus
• Powerful adductor of the glenohumeral joint
• Clavicular head can also aid in shoulder flexion
• In a flexed position, the lower fibres of the pectoralis major (sternocostal head) can also extend the shoulder (only as far as the anatomical position
3) Pectoralis minor
• Moves the scapula
• Innervated by the Medial Pectoral Nerve – roots C8, T1
• Stabilises and depresses the scapula
• Origin at usually 3 ribs in the range of 2-5, and sometimes all 4
• Inserts into the coracoid process of the scapula
• Functions is to stabilise scapula as the elbow and shoulder move around
• Anatomical action is to depress the scapula
4) Serratus anterior
• Moves scapula
• Innervated by Long Thoracic Nerve (C5, C6, C7)
• Origin is at the upper nine ribs
• Raps around the body wall and inserts onto the medial border of the scapula
• Grabs the scapula and pulls it to the front, which is pronation of the scapula
• Prevents winging of the scapula
• When pushing something heavy with the upper limb, the scapula wants to pull away from the body, due to the action from big anterior muscles
• Serratus anterior helps to hold the scapula against the body wall, which prevents the scapula from sticking up on the back
• If the long thoracic nerve is damaged during breast surgery or a chest drain insertion, this can lead to winging
Anterior neurovascular relations
What are the 3 extrinsic back muscles?
What do they each move?
Where are their origins and inserts?
• Extrinsic back muscles:
1) Latissimus Dorsi
• Moves the humerus
• Innervated by the Thoracodorsal Nerve (branch of posterior cord) – roots C6, C7, C8
• Attaches to spinous processes of T8-T12 via the Thoracolumbar fascia
• Inserts into the floor of the intertubercular sulcus between the 2 lips
• As it does this, it twists, so lowermost fibres become superior
• Extends, adducts, and medially rotates
2) Trapezius
• Moves the scapula
• Innervated by Spinal accessory nerve (Cranial Nerve 11) – roots C4, C5
• Only muscle that moves the upper limb and is not innervated by the brachial plexus
• Origin to the base of the skull at external occipital protuberance, nuchal ligament, spinous processes of C7-T12
• Inserts on to the acromion spine to the scapula and rapping around onto clavicle
• Superior part elevates scapula
• Middle part retracts scapula
• Inferior part depresses scapula
3) Rhomboids (major and minor)
• Moves the scapula
• Innervated by the Dorsal Scapular Nerve – roots C4, C5
• Has some cervical afferents for proprioception
• Rhomboid major and minor attach to the medial border of the scapula
• Rhomboid minor attaches mostly around where you find the spine
• Rhomboid major inferior to this
4) Levator Scapula
• Moves the scapula
• Innervated by the Cervical Nerve – roots C3, C4 and dorsal scapular nerve – roots C4, C5
• Insertion at the superior border of the scapula
What are the primary movers in these scapular movements?
1) Elevation
2) Depression
3) Protraction
4) Retraction
5) Upward rotation
6) Downward rotation
1) Elevation – Upper trapezius
2) Depression – Gravity
3) Protraction – Serratus Anterior
4) Retraction – Middle trapezius
5) Upward rotation – Upper trapezius and inferior part of Serratus Anterior
6) Downward rotation – Latissimus Dorsi
What are intrinsic shoulder muscles?
What are the 3 intrinsic shoulder muscles?
What are they innervated by?
Where are their origins and inserts?
What actions are they responsible for?
- Intrinsic shoulder muscles are muscles that run from the scapula to the humerus and moves the glenohumeral joint
- 3 intrinsic shoulder muscles:
1) Deltoid
• Innervated by the axillary nerve – roots C5 and C6
• U-shaped origin
• Origin at the clavicle, acromion, and the spine of the scapula
• All 3 parts converge and insert onto the deltoid tuberosity on the anterolateral aspect of the humerus (single insertion)
• Running between the deltoid and pectoralis major, there is the deltopectoral groove/triangle, which is where the cephalic vein is located
• The anterior part of the deltoid attaches to the clavicle, and is responsible for flexion and medial rotation of the GH joint
• The middle part attaches to the acromion, and is responsible for abduction of the GH joint
• The posterior part attaches to the spine of the scapula, and is responsible for flexion and extension of the GH joint
2) Teres Major
• Innervated by the lower subscapular nerve – roots C5 and C6
• Origin at the bottom of the scapula
• Raps around up onto the medial tips of the intertubercular sulcus of the humerus
• Responsible for adduction and medial rotation of the GH joint
3) Rotator cuff muscles (SITS)
What are the 4 rotator cuff muscles?
What are they each innervated by?
Where are their origins and inserts?
What movements are they each responsible for?
• 4 rotator cuff muscles:
1) Supraspinatus
• Innervated by suprascapular nerve – roots C4, C5, C6
• Origin above the spine of the scapula
• Inserts onto the greater tuberosity of the humerus
• Initiates abduction for first 15 degrees, ager that, the deltoid takes over
• Deltoid muscle needs to get the humerus away from the body before it can abduct
2) Infraspinatus
• Innervated by suprascapular nerve – roots C5 and C6
• Origin beneath the spine of the scapula
• Inserts onto the greater tuberosity of the humerus
• For external rotation
3) Teres Minor
• Innervated by the axillary nerve – C5 and C6
• Looks like teres major, but smaller and more superior
• Inserts onto the greater tuberosity of the humerus
• For external rotation
4) Subscapularis
• Upper and Lower subscapular nerves – roots C5, C6, C7
• Anterior surface of scapula
• Inserts onto the lesser tuberosity of the humerus
• For internal rotation
What is the most important function of the muscle in the rotator cuff?
How do these muscles attach to the humeral head?
Where is the GH joint weakest?
How is the GH joint most commonly dislocated?
Where is the most common and second most common place the humeral head can end up?
Where does the supraspinatus run?
What is also located here?
What can injury cause?
- The tone of rotator cuff muscles is the most important factor in GH joint stability, and are responsible for holding the humeral head in the glenoid fossa
- These muscles form a ring on the head of the humerus, which helps to support it
- The GH joint is weakest inferiorly
- The GH joint is most commonly dislocated when a downwards force gets applied to an outstretched arm, which pushes the humeral head down the way
- In 80% of GH dislocations, the humeral head ends up anteriorly, where the brachial plexus is
- 15-18% are inferior
- Nothing is superior without massive bony trauma
- The supraspinatus is located beneath the acromion process of the scapula, where subacromial bursa is also located
- This bursa can become inflamed and impinged
What is the fascia that rounds the pectoralis minor?
What is this continuous with?
What is the axillary fascia fused with?
Where is the pectoral fascia found?
What does it surround?
What is it continuous with?
What is the fascia found round the rest of the upper limb?
What is the fascia located posteriorly to the pectoral and scapular region?
What is this the origin of?
What does it separate?
- The Clavipectoral fascia surrounds the pectoralis minor, which is continuous with the axillary facia
- The axillary fascia is fused with the skin of the floor of the axilla, so when the arm is elevated, it pulls the skin up with it, giving the axillary fossa (armpit)
- The pectoral facia is found more anteriorly to the clavipectoral fascia, and surrounds the pectoralis major
- The pectoral fascia is also continuous with the axillary fascia
- Down the rest of the upper limn, there is the brachial fascia, which is a sock of fascial around the whole limb
- Posterior to the pectoral and scapular regions, we have the infraspinatus and supraspinatus fascia
- This is very thick dense tissue that acts as the origin for muscles
- It separates the infraspinatus and supraspinatus from muscles overlying them, such as the latissimus dorsi and the trapezius, allowing muscles to move independently over one another
What is the axilla?
What shape is it?
What are the 4 walls of the axilla?
What forms the floor?
What are the 3 contents of the Axilla?
- The axilla is a gateway that connects the neck to the upper limb
- The axilla has a pyramidal shape
- 4 walls of the axilla:
1) Anterior wall
• Pectoralis major
• Pectoralis minor
• Fascia
2) Posterior wall • Scapula • Subscapularis • Teres Major • Latissimus Dorsi
3) Medial wall
• Ribs 1-4
• Serratus Anterior
4) Lateral wall
• Humerus (intertubercular groove)
5) Floor
• Skin
• Axillary Fascia
• Contents of the axilla:
1) Axillary vessels
2) Brachial plexus
• Cords and branches
3) Axillary Sheath
• From prevertebral fascia
• Surrounds the neurovascular structures
• Continuous with deep fascia of the neck
• Blends with vessels when it comes to the arm
What 3 things do lymphatics of the axilla drain?
What does it contain?
What are the 5 groups of lymphatics in the axilla?
Where do these lymph nodes drain?
Where does the breast drain?
What drains the medial superficial arm?
What bypasses this?
Which of these lymph nodes are palpable?
• Lymphatics of the axilla drain:
1) The upper limb
2) Thoracic wall
3) Abdominal wall (to some extent
- Also contains the axillary tail of breast
- 5 Groups of lymphatics in the axilla:
1) Anterior (pectoral)
2) Lateral (humeral)
3) Posterior (subscapular)
4) Central
5) Apical
- These lymph nodes drain to the subclavian trunk, and on to respective lymph trunks
- The breast drains primarily to pectoral lymph nodes, and on to central lymph nodes
- The medial superficial arm is drained by humeral lymph nodes
- The lateral superficial arm bypasses this and go to the apical lymph nodes
- The humeral and pectoral lymph nodes are palpable
- The central lymph nodes are palpable, to some extent
What 2 vascular structures are anterior?
What do we then need?
What are the 3 scapular spaces?
How can their borders be remembered?
- The axillary artery and brachial plexus are anterior
- So, we then need structures to get these things to the posterior regions in the form of 3 scapular spaces
• The 3 scapular spaces are:
1) Upper triangular space
2) Quadrangular space
3) Lower triangular space
- Their borders can be remembered by making a hashtag shape with the fingers
- Middle finger is the humerus
- Index finger is the head of triceps
- The upper finger is the teres minor
- Lower finger is teres major
What are the 4 borders of the Quadrangular space?
What are its 2 contents?
• Borders of the quadrangular space:
1) Teres Minor
2) Teres Major
3) Humerus
4) Long Head of Triceps
• Contents:
1) Posterior circumflex humeral artery
2) Axillary nerve at the surgical neck of the humerus
What are the 3 borders of the upper triangular space?
What are its 1 contents?
• 3 borders of the upper triangular space:
1) Teres Minor
2) Teres Major
3) Long head of Triceps
• Contents:
1) Circumflex scapular artery
• Branch of subscapular artery
• Anastomoses with suprascapular artery
What are the 3 borders of the upper triangular space?
What are its 2 contents?
• 3 borders of the upper triangular space (triangular interval):
1) Lateral head of triceps
2) Long head of triceps
3) Teres Major
• Contents:
1) Radial nerve
2) Profunda brachii artery
• Leads to spiral groove (radial sulcus) on the humerus
