Anatomy of the scapular region and the back Flashcards
what muscles elevate the arm after 90 degrees
1) Serratus anterior moves/pulls the inferior angle
2) Trapezius pulls the scapula upwards
What is the movement of supraspinatus?
external/lateral rotation
What is the function of the subscapular muscle?
Medial rotation
Describe the deltoid muscle
It is a thick triangular muscle, forming the round contour of the shoulder
What is the origin of the deltoid muscle?
1) Anterior fibers: arises from the anterior border of the lateral 1/3 of the clavicle (clavicular head)
2) Middle (lateral) fibers: Arises from the lateral border of the acromion process (acromial head)
3) Posterior fibers: parallel, arise from the lower lip of the crest of the spine of the scapula (spinal/scapular head)
What is the site of insertion of the deltoid muscle?
Deltoid tuberosity of the humerus
What is the nerve supply of the deltoid muscle?
Axillary nerve (C5, 6) it also supplies teres minor
What are some of the symptoms of damage to the axillary nerve?
Atrophy of the deltoid muscle and loss of sensation in the shoulder skin
What are the actions of the deltoid muscle?
1) Anterior fibers: flexion (along with pectoralis major) and medial rotation of the arm
2) Posterior fibers: extension (along with latissimus dorsi) and lateral rotation of the arm
3) Middle fibers: chief muscle in the abduction of the shoulder (from 15-90 degrees)
What is the origin of the supraspinatus muscle?
Medial 2/3 of the supraspinous fossa
What is the site of insertion of the supraspinatus muscle?
Highest impression on the greater tuberosity of the humerus (greater tubercle)
FYI Teres minor and infraspinatus also insert into the greater tubercle inferiorly aiding in the lateral rotation of the arm
What is the nerve supply of the supra and infraspinatus?
subscapular nerve (branch of the upper trunk (of ventral rami of C5 & 6)
What are the actions/functions of the supraspinatus?
1) Initiates the abduction of the arm from 0-15 degrees
2) Stabilizes the shoulder joint (head of the humerus)
- FYI it is the only rotator cuff muscle that does not rotate the humerus
What is the origin of the infraspinatus?
Medial 2/3 of the infraspinous fossa
What is the site of insertion of the infraspinatus muscle?
Greater tubercle (middle impression), supplied by the subscapular nerve
What is the action/function of the infraspinatus muscle?
1) Lateral rotation of the arm (+ teres minor and the help of the posterior fibers of the deltoid muscle)
2) Steadies the head of the humerus during movements
- The most powerful lateral rotator cuff muscle
What is the origin of the subscapularis muscle?
Medial 2/3 of the subscapular fossa
Where is the subscapularis inserted?
Lesser tuberosity of the humerus
Which nerve innervates the subscapularis muscle?
Upper and lower subscapular nerve
The lower subscapular nerve also innervates teres major
What is the action of the subscapularis muscle?
1) Medial rotation of the arm
2) Stabilizes the head of the humerus during movement
What is the site of origin of teres minor?
Upper 2/3 of the back lateral border of the scapula
Where is teres minor inserted?
Lower impression of the greater tubercle
Supra and infraspinatus are also inserted to the greater tubercle
Which nerve supplies teres minor?
Axillary nerve along with the deltoid
What is the action of teres minor?
1) Adduction and lateral rotation of the arm
2) Stabilizes the shoulder joint
What is the origin of the teres major?
Lower 1/2 of the back of the lateral border of the scapula
Where is teres major inserted?
Medial lip of the bicipital groove of the humerus
What nerve innervates teres major?
Lower subscapular nerve (a branch of the posterior cord of the brachial plexus)
What is the action of teres major?
1) Extension
2) Adduction
3) Medial rotation of the arm
SIDE NOTES
1) LATERAL BORDER OF THE SCAPULA IS THE ORIGIN FOR TERES MINOR AND TERES MAJOR
2) MEDIAL BORDER OF THE SCAPULA IS THE SITE OF INSERTION OF SERRATUS ANTERIOR
3) LATERAL LIP OF THE HUMERUS IS THE SITE OF PECTORALIS MAJOR INSERTION
4) MEDIAL LIP OF THE HUMERUS IS THE SITE OF INSERTION FOR TERES MAJOR
5) THE FLOOR OF THE SCAPULA IS THE SITE OF INSERTION FOR THE LATISSIMUS DORSI
What forms the rotator cuff?
- four muscles
1) Supraspinatus
2) Infraspinatus
3) Teres minor
4) subscapularis
What is the function of the rotator cuff muscles?
The tone of these muscles helps in holding the head of the humerus in the glenoid cavity of the scapula during movement, assisting in the stability of the shoulder joint
What is the role of the intermuscular spaces?
Where nerves/artery goes from anterior to posterior and vice versa, they can go through the compartments either by piercing the septum or via the intermuscular spaces
What are the different intermuscular spaces?
1) Quadrangular space
2) Upper triangular space
3) Lower triangular space
What is the boundaries of the quadrangular intermuscular space?
1) Long head of the triceps medially
2) Humerus laterally
3) Teres minor superiorly
4) Teres major inferiorly
What are the borders of the lower triangular space?
1) Teres major superiorly
2) Humerus laterally
3) Long head of triceps medially
What are the borders of the upper triangular space?
1) Teres minor superiorly
2) Long head of the triceps laterally
4) Teres major inferiorly
What structures pass through the quadrangular space?
1) Axillary nerve (around the surgical neck)
2) Posterior humeral circumflex artery
What structures pass through the lower triangular space?
1) Radial nerve
2) Brofunda brachii
- They will pass through the radial groove going to the lateral compartment
What structures pass through the lower triangular space?
1) Circumflex scapular artery (anastomoses around the scapula)
What are the arteries that participate in anastomoses around the scapula?
- Allows the blood follow in case of any injury
- The branches arise from the subclavian and axillary artery
- The subclavian artery gives (thyrocervical trunk that branches to give transverse cervical artery and the suprascapular artery)
- The suprascapular artery will give a deep branch of an artery on the medial border of the scapula called (transverse cervical artery)
- The deep branch of the transverse cervical artery will anastomose with the circumflex scapular artery (a branch of the axillary artery)
- The Axillary artery will give rise to the subscapular artery that will branch to give the circumflex scapular artery and also give rise to the thoracodorsal artery
What is the origin of the artery that passes through the lower triangular space?
It is the profunda that comes from the brachial
- Origin is the brachial artery
What is the origin of the nerve that passes through the lower triangular space?
It is the radial nerve and its origin is the posterior cord of the brachial plexus
What are the muscles of the back?
- Attaches the upper limb to the trunk
A) Superficial layer:
1) Trapezius
2) Latissimus dorsi
B) Deep layer:
1) Levator scapulae
2) Rhomboideus minor
3) Rhomboideus major
What is the origin of the trapezius?
1) External occipital protuberance and the medial 1/3 of the superior nuchal line
2) Ligamentum nuchae and spine of the 7th cervical vertebrae
3) Spine of all thoracic vertebrae and the corresponding supraspinous ligaments
What is the site of insertion of the trapezius muscle?
1) Upper fibers attaches to the posterior border and lateral 1/3 of the scapula
2) Middle fibers attach to the medial border of the acromion and the upper lip of the crest of the spine of the scapula
3) Lower fibers attach to the tubercle on the lower lip of the crest of the spine
What is the nerve supply of the trapezius muscle?
1) Spinal accessory nerve (motor)
2) 3rd & 4th cervical nerves (proprioceptive)
What is the action of the trapezius muscle?
1) Upper fibers elevate the scapula and shoulder
2) Middle fibers retract the scapula
3) Lower fibers depress the medial part of the scapula
4) All fibers act to abduct the arm after 90 degrees (over the head) “with the help of other muscles like serratus anterior”
What is the origin of the latissimus dorsi?
1) Lower 6 thoracic spines under the trapezius
2) Thoracolumbar fascia
3) Outer lip of the iliac crest
4) Lower 3/4 ribs
5) Back of the inferior angle of the scapula
Where is the site of insertion of the latissimus dorsi?
floor of the bicipital groove of the humerus
What is the nerve supply of the latissimus dorsi?
The nerve to latissimus dorsi (thoracodorsal nerve) “C6, 7, & 8”
What is the action of the latissimus dorsi?
1) Adduction
2) Extension
3) Medial rotation
4) Drawing the arm down from above the head (in climbing)
5) Helps in all violent expiratory movement
6) Latissimus dorsi & pectoralis major muscles help in climbing on a tree
What is the origin of the levator scapulae muscle?
Transverse process of the upper 4 cervical vertebrae
What is the site of insertion of the levator scapulae muscle?
Back of the medial border of the scapula (from the upper angle of the scapula to the spine of the scapula)
What is the nerve supply of the levator scapulae?
1) Dorsal scapular nerve (nerve to rhomboid, motor, C5)
2) 3rd & 4th cervical nerves (propioreceptive)
What is the action of the levator scapulae?
1) Elevation of the scapula
2) Assists in rotation of the scapula downwards and depresses the shoulder
What is the origin of the rhomboid muscles?
Spinous process of the T2-T5 vertebrae
What is the nerve that supplies rhomboids?
Posterior scapular nerve
Where is rhomboid major inserted?
Inserts to the medial border of the scapula inferior to the rhomboid minor
Where is rhomboid minor inserted?
What is the function of the rhomboids?
Important retractors
What is the triangle of auscultation in the back and what are its borders?
- To auscultate the lungs
1) Medially/superiorlly: lateral border of the trapezius
2) Inferiorly: upper border of the latissimus dorsi
3) Laterally: medial border of the scapula
4) Floor: rhomboid major
A patient has a problem with adducting and medially rotating the arm which muscle is most probably impaired?
Teres major
If a patient has a problem with abducting the arm over the head which muscle will be impaired?
Supraspinatus
