Shoulder Muscles

Question 1

Subclavius

Answer 1

Origin first rib
Insertion groove inferior surface of the clavicle
Function: depressed shoulder protects the underlying brachial plexus and subclavian vessels from fracture to the clavicle
Nerve: own nerve from brachial plexus

Question 2

Serratus anterior

Answer 2

Origin: 1-9 or 1-8 ribs two slips from the second rib

Insertion: medial border of the scapula between the superior and inferior angles along with insertion into the thoracic vertebrae

Relation: deep to subscapularis seperated by subscapular bursa and from the rib inferiority by scapula thoracic bursa

Innervation: long thoracic nerve (nerve of bell) damage to this nerve leads to winged scapula

Function: protraction of scapula, pull scapular forward which is essential for ante version of the arm, lift the ribs when shoulder girdle is fixed assisting in respiration e

Question 3

Pec major

Answer 3

Origin: clavicular head: medial half of anterior surface of the clavicle runs almost horizontal,
stero costal head lateral half of the anterior part of he nmanubrium and body of sternum upper 6 costal cartilage

Insertion: lateral lib of bicitpial sulcus of humerus (clavicular fibres superficial, stereo costal fibres deep)

Innervation: medial and lateral pectoral nerves from medial and lateral cords of the brachial plexus( only muscle supplied by all 5 segments of the plexus)

Action: medial rotation, adduction flexion is shoulder accessory muscle in inspiration

Question 4

Pec minor

Answer 4

Origin: 3,4,5 runs under pec major

Insertion: short thick tendon into medial/upper surface of coracoid process of scapula

Nerve: medial and lateral pectoral nerves from medial and lateral cords of the brachial plexus

Action protraction of shoulder returns shoulder to rest position after rotation

Question 5

Trapezius

Answer 5

Origin: middle third of superior nuchal line to spine of C7 along ligament nuchae spinous process and supra spinous process of all 12 thoracic vertebrae
Insertion: upper fibres: - posterior part of lateral 3rd of clavicle

Middle fibres: medial border is a acromion/superior lip of crest is scapular

Lower fibres – Middle end of spine of scapula

Innervation: spinal part of the accessory nerve

Action: descending part elevates, ascending part depresses and middle or both retract ascending and de sending parts act together to rotate the Glenood cavity superiorly

Question 6

Latissimus Dorsi

Answer 6

Origin: spines is lower 6 thoracic vertebrae, slips from the lower 4 ribs and inferior angle of scapular, and from the iliac crest

Insertion: fibres pass under trapezius and converge to form posterior axilary fold spiral around lower border of teres major and form a broad white ligament attach to floor of intertubercular sulcus
Inervation: thoracodorsal

Action: extension, adduction, medial rotation, used in cough to compress chest

Question 7

Rhomboids

Answer 7

Origin: major: spines of t2-t5 and intervening sipraspinous ligaments
Minor: spines of c7,t1
Insertion
Major:medial border of scapular between root of spine and inferior angle
Minor medial border of scapular at root of spine
Inervation: dorsal scapular from c5
Action: rotation of scapular to the rest position retracts scapula j

Question 8

Levator scapulae

Answer 8

Origin: transverse process of atlas and axis and posterior tubercles of c3 and c4
Insertion: upper part of medial border of scapular
Inervation: cervical plexus and dorsal scapular nerve
Action elevation of scapular

Question 9

Deltoid

Answer 9

Origin: lateral third of clavicle, acromion and spine of scapula

Insertion: deltoid tuberosity of humerus

Innervation: axilary nerve

Action: anterior part: flexes and medially rotates arm
Middle part abducts the arm
Posterior part extends and laterally rotates

Question 10

Supraspinatus

Answer 10

Origin: suprraspinous fossa of scapula
Insertion: superior facet greater tubercle of humerus

Innervation: supra scapular nerve

Action initiates and assist deltoid in adduction stabiliser

Question 11

Infra spinatus

Answer 11

Infra spinous fossa of scapular

Insertion: Middle facet greater tubercle of humerus

Innervation supra scapular

Action: laterally rotates arm help holds humeral head in glenouid cavity

Question 12

Teres minor

Answer 12

Origin: Middle part of lateral border of scapular

Insertion: infer facet of greater tubercle of humerus

Innervation: axilary

Action : later rotation and glenouid head stabilisation

Question 13

Teres major

Answer 13

Origin: posterior surface of inferior angle of scapular

Insertion: medial lip of intertubercular groove

Innervation: lower subscapular

Action: adducts and medially rotates the arm

Question 14

Subscapularis

Answer 14

Origin: subscapular fossa

Insertion lesser tubercle of humerus

Innervation: upper and lower subscapular nerve

Action medially rotates and adducts arm helps hold humeral head in glenoid cavity