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