Posterior Shoulder Muscles: Anatomy and Function
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Questions and Answers

Which of the following muscles is NOT a part of the Scapulo-humeral (Intrinsic) Muscles group?

  • Deltoid
  • Latissimus dorsi (correct)
  • Teres Major
  • Rotator Cuff muscles
  • What is the origin of the Trapezius muscle?

  • Medial third of superior nuchal line, external occipital protuberance, and nuchal ligament (correct)
  • Transverse processes of C1-C4 vertebrae
  • Spinous processes of C7-T12 vertebrae
  • Iliac crest, inferior 3 or 4 ribs
  • Which nerve is responsible for the action of the Latissimus dorsi muscle?

  • Thoracodorsal Nerve (correct)
  • Dorsal Scapular Nerve
  • C3,4 Nerve
  • Accessory Nerve
  • What is the insertion point of the Levator Scapulae muscle?

    <p>Medial border of scapula superior to root of spine</p> Signup and view all the answers

    What is the action of the Levator Scapulae muscle?

    <p>Elevates medial border of scapula</p> Signup and view all the answers

    Which of the following muscles is a part of the Deep (Extrinsic) Muscles group?

    <p>Rhomboids</p> Signup and view all the answers

    What is the origin of the Rhomboids muscle?

    <p>Spinous processes of C7 and T1 vertebrae, and T2-T5 vertebrae</p> Signup and view all the answers

    What is the origin of the Deltoid muscle?

    <p>Lateral third of clavicle; acromion and spine of scapula</p> Signup and view all the answers

    What is the action of the Teres Major muscle?

    <p>Adducts and medially rotates arm</p> Signup and view all the answers

    Which nerve innervates the Supraspinatus muscle?

    <p>Suprascapular nerve (C4, C5, C6)</p> Signup and view all the answers

    What is the action of the Infraspinatus muscle?

    <p>Laterally rotates arm</p> Signup and view all the answers

    What is the insertion of the Subscapularis muscle?

    <p>Lesser tubercle of humerus</p> Signup and view all the answers

    Which muscle is not a part of the Rotator Cuff?

    <p>Teres Major</p> Signup and view all the answers

    What is the origin of the Infraspinatus muscle?

    <p>Infraspinous fossa of scapula</p> Signup and view all the answers

    What is the action of the anterior part of the Deltoid muscle?

    <p>Flexes and medially rotates arm</p> Signup and view all the answers

    Study Notes

    Back Muscles (Posterior Shoulder Muscles)

    • Divided into three groups: superficial (extrinsic), deep (extrinsic), and scapulo-humeral (intrinsic) muscles

    Superficial (Extrinsic) Muscles

    • Trapezius
      • Origin: medial third of superior nuchal line, external occipital protuberance, nuchal ligament, and spinous processes of C7-T12 vertebrae
      • Insertion: lateral third of clavicle, acromion, and spine of scapula
      • Innervation: accessory nerve (C3, C4)
      • Action: acts on scapula
    • Latissimus dorsi
      • Origin: spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs
      • Insertion: floor of intertubercular groove of humerus
      • Innervation: thoracodorsal nerve (C6, C7, C8)
      • Action: extends, adducts, and medially rotates humerus

    Deep (Extrinsic) Muscles

    • Levator scapulae
      • Origin: transverse processes of C1-C4 vertebrae
      • Insertion: medial border of scapula superior to root of spine
      • Innervation: dorsal scapular nerve (C5)
      • Action: elevates medial border of scapula
    • Rhomboids
      • Minor: origin - nuchal ligament and spinous processes of C7 and T1 vertebrae
      • Minor: insertion - smooth triangular area at medial end of scapular spine
      • Major: origin - spinous processes of T2-T5 vertebrae
      • Major: insertion - medial border of scapula from level of spine to inferior angle
      • Innervation: dorsal scapular nerve
      • Action: retraction and medial rotation of scapula

    Scapulo-humeral (Intrinsic) Muscles

    • Deltoid
      • Origin: lateral third of clavicle, acromion, and spine of scapula
      • Insertion: deltoid tuberosity of humerus
      • Innervation: axillary nerve (C5, C6)
      • Action: anterior part - flexes and medially rotates arm, middle part - abducts arm, posterior part - extends and laterally rotates arm
    • Teres Major
      • Origin: posterior surface of inferior angle of scapula
      • Insertion: medial lip of intertubercular groove of humerus
      • Innervation: lower subscapular nerve (C5, C6)
      • Action: adducts and medially rotates arm

    Rotator Cuff Muscles

    • Four intrinsic shoulder muscles: supraspinatus, infraspinatus, teres minor, and subscapularis
    • They rotate and stabilize the shoulder joint

    Rotator Cuff Muscles (Detailed)

    • Supraspinatus
      • Origin: superior facet of greater tubercle of humerus
      • Insertion: suprascapular fossa of scapula
      • Innervation: suprascapular nerve (C4, C5, C6)
      • Action: initiates and assists deltoid in abduction of arm
    • Infraspinatus
      • Origin: middle facet of greater tubercle of humerus
      • Insertion: infraspinous fossa of scapula
      • Innervation: suprascapular nerve (C5, C6)
      • Action: laterally rotates arm
    • Teres Minor
      • Origin: middle part of lateral border of scapula
      • Insertion: inferior facet of greater tubercle of humerus
      • Innervation: axillary nerve
      • Action: laterally rotates arm
    • Subscapularis
      • Origin: subscapular fossa (most of anterior surface of scapula)
      • Insertion: lesser tubercle of humerus
      • Innervation: upper and lower subscapular nerves (C5, C6, C7)
      • Action: medially rotates and adducts arm

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    Description

    This quiz covers the anatomy and function of the back muscles, including the superficial, deep, and scapulo-humeral muscles. Learn about the origin, insertion, innervation, and action of each muscle.

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