Upper Back Anatomy

Question 1

Pectoralis Major - AFI

Answer 1

Attachments - Distal attachment of both heads is into the intertubular sulcus of the humerus
Clavicular head originates from the anterior surface of the medial clavicle
Sternocostal head originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle
Function - Adducts and medially rotates the upper limb, and draws the scapular anteroinferiorly. Theclavicular headalso acts individually to flex the upper limb
Innervation - Lateral and medial pectoral nerves

Question 2

Pectoralis Minor - AFI

Answer 2

Attachments - Originates from the 3rd-5th ribs, and inserts into the coracoid process of the scapula
Function - Stabilizes the scapula by drawing it anteroinferiorly against the thoracic wall
Innervation - Medial pectoral nerve

Question 3

Serratus Anterior - AFI

Answer 3

Attachments - consists of several strips, which originate from the lateral aspects of ribs 1-8. They attach to the costal (rib facing) surface of the medial border of the scapula
Function - Rotates the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the ribcage
Innervation - Long thoracic nerve

Question 4

Subclavius - AFI

Answer 4

Located directly underneath the clavicle, running horizontally. It affords some minor protection to the underlying neurovascular structures (e.g in cases of clavicular fracture or other trauma)
Attachments - Originates from the junction of the 1st rib and its costal cartilage, inserting into the inferior surface of the middle third of the clavicle
Function - Anchors and depresses the clavicle
Innervation - Nerve to subclavius

Question 5

State the borders of axilla

Answer 5

Apex - Also known as the axillary inlet, this is formed by lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle
Lateral wall - Formed by intertubercular groove of the humerus
Medial wall - Consists of the serratus anterior and the thoracic wall (ribs and intercostal muscles)
Anterior wall - Contains the pectoralis major and the underlying pectoralis minor and the subclavius muscles
Posterior wall - Formed by the subscapularis, teres major and latissimus dorsi

Question 6

Deltoid - AFI

Answer 6

Attachments - originates from the scapula and clavicle and attaches to deltoid tuberosity
Innervation - axillary nerve
Actions - anterior fibres are a powerful flexor, posterior fibres are a extensor, lateral fibres are an abductor

Question 7

Teres Major - AFI

Answer 7

Attachments - originates from posterior surface of the inferior angle of the scapula and attaches to the intertubercular groove of the humerus
Innervation - lower subscapular nerve
Actions - adducts the shoulder and medially rotates the arm

Question 8

State the 4 rotator cuff muscles

Answer 8

Subscapularis, infrapsinatus, supraspinatus, teres minor

Question 9

Subscapularis - AFI

Answer 9

Attachments - scapula into lesser tubercle of the humerus
Action - medial rotation and extension of the arm
Innervation - subscapular nerve

Question 10

Supraspinatus - AFI

Answer 10

Attachments - scapula into greater tubercle of humerus
Action - abduction of the arm
Innervation - suprascapular nerve

Question 11

Infraspinatus - AFI

Answer 11

Attachments - scapula to greater tubercle of humerus
Action - lateral rotation of arm
Innervation - suprascapular nerve

Question 12

Teres Minor - AFI

Answer 12

Attachments - scapula to greater tubercle of humerus
Action - lateral rotation and adduction of the arm
Innervation - axillary nerve

Question 13

State the extrinsic muscles of the upper back and its similarity in attachments

Answer 13

Trapezius, latissimus dorsi, levator scapulae, rhomboids

All originates from the torso and attach to bones of the shoulder

Question 14

Trapezius - AFI

Answer 14

Attachments - originates from the skull,nuchalligament and thespinous processes of C7-T12
The fibres attach to the clavicle, acromion and the scapula spine
Innervation - motor innervation is from the accessory nerve
Receives proprioceptor fibres from C3 and C4 spinal nerves
Action - upper fibres of the trapezius elevate the scapula and rotates it during abduction of the arm
Middle fibres retract the scapula and the lower fibres pull the scapula inferiorly

Question 15

Latissimus dorsi - AFI

Answer 15

Attachments - originates from lower part of back and fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus
Innervation - thoracordorsal nerve
Actions - extends, adducts and medially rotates the upper limb

Question 16

Levator scapulae - AFI

Answer 16

Attachments - begins in the neck, and descends to attach to the scapula
Innervation - dorsal scapula nerve
Actions - elevates the scapula

Question 17

Rhomboids - AFI

Answer 17

Attachments - originates in spinal cord and attaches to medial border or scapula
Innervation - dorsal scapula nerve
Actions - retracts and rotates scapula