Shoulder Muscles

1. What is the action of the Pectoralis Major muscle?

Raises and lowers the scapula

Flexes and extends the knee

Abducts and laterally rotates humerus

Action: Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly; acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed positionLateral Attachment: Lateral lip of intertubercular sulcus (groove) of humerusMedial Attachment: Clavicular head: anterior surface of medial half of clavicle Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle

The Pectoralis Major muscle is responsible for adducting and medially rotating the humerus, as well as drawing the scapula anteriorly and inferiorly. Additionally, its clavicular head can flex the humerus while the sternocostal head extends it from a flexed position.

Explanation

The Pectoralis Major muscle is responsible for adducting and medially rotating the humerus, as well as drawing the scapula anteriorly and inferiorly. Additionally, its clavicular head can flex the humerus while the sternocostal head extends it from a flexed position.

2. What is the action of the Pectoralis Minor muscle?

Action: Extends the forearm at the elbow joint

Action: Flexes the thigh at the hip joint

Action: Adducts the arm at the shoulder joint

Action: Stabilizes scapula by drawing inferiorly and anteriorly against thoracic wallLateral Attachment: Medial boarder and superior surface of coracoid process of scapulaMedial Attachment: 3rd-5th ribs near their costal cartilages

The Pectoralis Minor muscle is responsible for stabilizing the scapula by drawing inferiorly and anteriorly against the thoracic wall.

Explanation

The Pectoralis Minor muscle is responsible for stabilizing the scapula by drawing inferiorly and anteriorly against the thoracic wall.

3. What is the action of the subclavius muscle?

Originates from the sternum

Attaches to the acromion process

Increases range of motion in the shoulder joint

Action: Anchors and depresses clavicleLateral Attachment: Inferior surface of middle third of clavicleMedial Attachment: Junction of 1st rib and its costal cartilage

The subclavius muscle is responsible for anchoring and depressing the clavicle. It does not increase range of motion in the shoulder joint, attach to the acromion process, or originate from the sternum.

Explanation

The subclavius muscle is responsible for anchoring and depressing the clavicle. It does not increase range of motion in the shoulder joint, attach to the acromion process, or originate from the sternum.

4. What is the action of the Trapezius muscle?

Action: Descending (superior) part elevates; ascending (inferior) part depresses; and middle part (or all parts together) retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorlyLateral Attachment: Lateral third of clavicle; acromion and spine of scapulaMedial Attachment: Medial third of superior nuchal line; external occipital protuberance; nuchal ligament; spinous processes of C7-T12 vertebrae

Action: Flexes the elbow

Action: Extends the knee

Action: Raises the arm

The Trapezius muscle is responsible for various actions including elevating, depressing, retracting the scapula, and rotating the glenoid cavity superiorly.

Explanation

The Trapezius muscle is responsible for various actions including elevating, depressing, retracting the scapula, and rotating the glenoid cavity superiorly.

5. What is the action of the Latissimus Dorsi muscle?

Action: Flexes the elbow and forearm

Action: Extends, adducts, and medially rotates humerus; raises body toward arms during climbingLateral Attachment: Floor of intertubercular sulcus (groove) of humerusMedial Attachment: Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs

Action: Abducts the shoulder and rotates it laterally

Action: Flexes the knee

The Latissimus Dorsi muscle is responsible for extending, adducting, and medially rotating the humerus, and raising the body toward the arms during climbing. It does not have the actions mentioned in the incorrect answers.

Explanation

The Latissimus Dorsi muscle is responsible for extending, adducting, and medially rotating the humerus, and raising the body toward the arms during climbing. It does not have the actions mentioned in the incorrect answers.

6. Levator Scapulae (Deep posterior extrinsic muscle)

Action: Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapulaLateral Attachment: Medial border of scapula superior to root of spineMedial Attachment: Posterior tubercles of transverse processes of C1-C4 vertebrae

Incorrect Answer 2: Action: Abducts scapula and tilts its glenoid cavity inferiorly by rotating scapulaLateral Attachment: Medial border of scapula inferior to root of spineMedial Attachment: Anterior tubercles of transverse processes of C1-C4 vertebrae

Incorrect Answer 1: Action: Depresses scapula and tilts its glenoid cavity superiorly by rotating scapulaLateral Attachment: Lateral border of scapula superior to root of spineMedial Attachment: Posterior tubercles of transverse processes of C1-C4 vertebrae

Incorrect Answer 3: Action: Adducts scapula and tilts its glenoid cavity superiorly by rotating scapulaLateral Attachment: Lateral border of scapula inferior to root of spineMedial Attachment: Posterior tubercles of transverse processes of C5-C7 vertebrae

Explanation: The Levator Scapulae muscle is responsible for elevating the scapula and tilting its glenoid cavity inferiorly by rotating the scapula. Its attachments are to the medial border of the scapula superior to the root of the spine and the posterior tubercles of the transverse processes of C1-C4 vertebrae.

Explanation

Explanation: The Levator Scapulae muscle is responsible for elevating the scapula and tilting its glenoid cavity inferiorly by rotating the scapula. Its attachments are to the medial border of the scapula superior to the root of the spine and the posterior tubercles of the transverse processes of C1-C4 vertebrae.

7. What is the action of the Rhomboid minor and major muscles?

Action: Rotate the shoulder joint

Action: Retract scapula and rotate it to depress glenoid cavity; fix scapula to thoracic wallLateral Attachment: Minor: triangular area at medial end of scapular spine Major: medial border of scapula from level of spine to inferior angleMedial Attachment: Minor: nuchal ligament; spinous processes of C7 and T1 vertebrae Major: spinous processes of T2-T5 vertebrae

Action: Elevate the scapula

Action: Flex the elbow joint

The Rhomboid minor and major muscles are not responsible for flexing the elbow joint, rotating the shoulder joint, or elevating the scapula. Their primary action is to retract the scapula and rotate it to depress the glenoid cavity, while also fixing the scapula to the thoracic wall.

Explanation

The Rhomboid minor and major muscles are not responsible for flexing the elbow joint, rotating the shoulder joint, or elevating the scapula. Their primary action is to retract the scapula and rotate it to depress the glenoid cavity, while also fixing the scapula to the thoracic wall.

8. What is the primary action of the deltoid muscle?

Action: Pectoralis major abducts and horizontally flexes the arm

Action: Biceps brachii flexes and supinates the forearm

Action: Clavicular (anterior) part flexes and medially rotates arm; acromial (middle) part abducts arm; spinal (posterior) part extends and laterally rotates armDistal Attachment: Deltoid tuberosity of humerusProximal Attachment: Lateral third of clavicle; acromion and spine of scapula

Action: Triceps brachii extends and adducts the arm

The deltoid muscle is responsible for various actions depending on its parts, including flexing, rotating, and abducting the arm.

Explanation

The deltoid muscle is responsible for various actions depending on its parts, including flexing, rotating, and abducting the arm.

9. What is the function and attachment points of the supraspinatus muscle?

Action: Adducts the armDistal Attachment: Medial lip of intertubercular groove of humerusProximal Attachment: Anterior surface of scapula

Action: Extends the knee jointDistal Attachment: Tibial tuberosityProximal Attachment: Ischial tuberosity

Action: Flexes the elbow jointDistal Attachment: Olecranon of ulnaProximal Attachment: Medial epicondyle of humerus

Action: Initiates and assists deltoid in abduction of arm and acts with other rotator cuff musclesDistal Attachment: Superior facet of greater tubercle of humerusProximal Attachment: Supraspinous facia of scapula

The supraspinatus muscle is involved in the initiation and assistance of the deltoid in arm abduction, along with other rotator cuff muscles. Its distal attachment is on the superior facet of the greater tubercle of the humerus, while its proximal attachment is on the supraspinous fascia of the scapula.

Explanation

The supraspinatus muscle is involved in the initiation and assistance of the deltoid in arm abduction, along with other rotator cuff muscles. Its distal attachment is on the superior facet of the greater tubercle of the humerus, while its proximal attachment is on the supraspinous fascia of the scapula.

10. What is the action of the Infraspinatus muscle?

Extend the shoulder

Action: Laterally rotate arm; help hold humeral head in glenoid cavity of scapulaDistal Attachment: Middle Facet of greater tubercle of humerusProximal Attachment: Infraspinous fossa of scapula

Adduct the arm

Flex the forearm

11. What is the action of the Teres Minor muscle?

Action: Laterally rotate arm; help hold humeral head in glenoid cavity of scapulaDistal Attachment: Inferior facet of greater tubercle of humerusProximal Attachment: Middle part of lateral border of scapula

Inwardly rotate arm; help stabilize the elbow joint

Extend the knee; support the lumbar spine

Flex the wrist; assist in shoulder abduction

The Teres Minor muscle is responsible for laterally rotating the arm and helping hold the humeral head in the glenoid cavity of the scapula. Its distal attachment is the inferior facet of the greater tubercle of the humerus, and its proximal attachment is in the middle part of the lateral border of the scapula.

Explanation

The Teres Minor muscle is responsible for laterally rotating the arm and helping hold the humeral head in the glenoid cavity of the scapula. Its distal attachment is the inferior facet of the greater tubercle of the humerus, and its proximal attachment is in the middle part of the lateral border of the scapula.

12. What is the action and attachments of the Teres Major muscle?

Action: Abducts and laterally rotates arm, Distal Attachment: Lateral epicondyle of humerus, Proximal Attachment: Anterior surface of clavicle

Action: Adducts and medially rotates armDistal Attachment: Medial lip of intertubercular groove of humerusProximal Attachment: Prosterior surface of inferior angle of scapula

Action: Flexes and supinates forearm, Distal Attachment: Olecranon process of ulna, Proximal Attachment: Lateral supracondylar ridge of humerus

Action: Extends and pronates wrist, Distal Attachment: Base of 2nd and 3rd metacarpal bones, Proximal Attachment: Medial epicondyle of humerus

The Teres Major muscle is responsible for adducting and medially rotating the arm, with distal attachment on the medial lip of the intertubercular groove of the humerus and proximal attachment on the posterior surface of the inferior angle of the scapula.

Explanation

The Teres Major muscle is responsible for adducting and medially rotating the arm, with distal attachment on the medial lip of the intertubercular groove of the humerus and proximal attachment on the posterior surface of the inferior angle of the scapula.

13. What is the action, distal attachment, and proximal attachment of the Subscapularis muscle?

Action: Medially rotates and adducts arm; helps hold humeral head in glenoid cavityDistal Attachment: Lesser tubercle of humerusProximal Attachment: Subscapular fossa (most of anterior surface of scapula)

Action: Flexes and adducts arm; attaches to the coracoid process of scapulaDistal Attachment: Medial epicondyle of humerusProximal Attachment: Supraspinous fossa

Action: Extends and laterally rotates arm; attaches to the acromion process of scapulaDistal Attachment: Radial tuberosityProximal Attachment: Lateral border of scapula

Action: Laterally rotates and abducts arm; attaches to greater tubercle of humerusProximal Attachment: Infraspinous fossaDistal Attachment: Coracoid process of scapula

The correct answer provided details the specific action, distal attachment, and proximal attachment of the Subscapularis muscle. The incorrect answers present different actions, distal attachments, and proximal attachments of other muscles, leading to a clear distinction from the correct answer.

Explanation

The correct answer provided details the specific action, distal attachment, and proximal attachment of the Subscapularis muscle. The incorrect answers present different actions, distal attachments, and proximal attachments of other muscles, leading to a clear distinction from the correct answer.