Axio-appendicular Muscles (extrinsic; Anterior) MA

Question 1

Subclavius Muscle (Origin, insertion, innervation, main action)

Answer 1

Origin: Junction of 1st rib and 1st costal cartilage

Insertion: Inferior surface of middle third of clavicle (inferior aspect)

Innervation: Subclavian nerve

Main action: anchors and depresses the clavicle

Question 2

Serratus Anterior Muscle (Origin, insertion, innervation, main action)

Answer 2

Origin: external surface of the lateral parts of the 1st through 8th-10th ribs

Insertion: Anterior (costal) surface of the medial border of the scapula

Innervation: long thoracic nerve (C5-C7)

Main action: protracts the scapula and holds it against the thoracic wall; rotates the scapula upwards

Question 3

Pectoralis Major Muscle (Origin, insertion, innervation, main action)

Answer 3

Origin:
-Clavicular head: anterior surface of the clavicle
-Sternocostal head: anterior surface of the sternum and superior six costal cartilages.
-Abdominal head: aponeurosis of external oblique

Insertion: Lateral lip of the intertubercular sulcus of humerus

Innervation: lateral and medial pectoral nerves.

Main actions: adducts and medially rotates the glenohumeral joint.
-Acting alone: clavicular head flexes the shoulder and sternocostal head extends the shoulder from flexed position.

Question 4

Pectoralis Minor (Origin, insertion, innervation, main action)

Answer 4

Origin: 3rd to 5th ribs near the costal cartilages

Insertion: medial border and superior surface of coracoid process of scapula

Innervation: medial pectoral nerve

Main actions: stabilizes the scapula by drawing It inferiorly and anteriorly against thoracic wall (protracts scapula)