Shoulder Anatomy and Movement Quiz
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Questions and Answers

Which muscle is primarily responsible for the upward rotation of the scapula during shoulder abduction?

  • Pectoralis minor
  • Infraspinatus
  • Upper trapezius (correct)
  • Deltoid

    • What is the main action of the serratus anterior in shoulder movement?

  • Scapular protraction (correct)
  • Shoulder adduction
  • Scapular retraction
  • Shoulder extension

    • Which of the following muscles acts as a distal mobilizer in the shoulder?

  • Upper trapezius
  • Deltoid (correct)
  • Serratus anterior
  • Rhomboids

    • What condition is associated with weakness of the serratus anterior?

    <p>Scapular winging</p> Signup and view all the answers

    Which muscles work together to prevent excessive superior translation of the humerus during shoulder abduction?

    <p>Infraspinatus and teres minor</p> Signup and view all the answers

    What is the angle of the clavicle's long axis relative to the frontal plane?

    <p>20 degrees</p> Signup and view all the answers

    Which movement combines abduction and flexion in the scapular plane?

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

    How is the humeral head positioned in relation to the M-L axis through the elbow?

    <p>30 degrees posteriorly</p> Signup and view all the answers

    What type of joint is mainly involved in the movement of the shoulder complex?

    <p>Sternoclavicular joint</p> Signup and view all the answers

    Which movement is associated with the upward and downward tilt of the glenoid fossa?

    <p>Scapular tilt</p> Signup and view all the answers

    What happens during internal rotation of the AC joint?

    <p>The medial border of the scapula pivots away from the thorax</p> Signup and view all the answers

    Which type of AC joint dislocation is characterized by complete tearing of the AC and partial tearing of the CC ligaments?

    <p>Type II</p> Signup and view all the answers

    In which plane does the glenoid fossa undergo anterior tilting during scapular motion?

    <p>Sagittal plane</p> Signup and view all the answers

    What is the functional significance of motion at the AC joint?

    <p>It optimally aligns the scapula against the thorax</p> Signup and view all the answers

    Which type of joint is the scapulothoracic joint classified as?

    <p>Not a true joint, separated by muscle</p> Signup and view all the answers

    How much range of motion (ROM) is associated with the sagittal plane rotational adjustments of the scapula?

    <p>5-30°</p> Signup and view all the answers

    During external rotation of the AC joint, which direction does the medial border of the scapula pivot?

    <p>Toward the thorax</p> Signup and view all the answers

    Which ligament prevents excessive downward rotation at the end range of motion at the AC joint?

    <p>Capsule (inferior portion)</p> Signup and view all the answers

    Which muscle is considered the most effective upward rotator of the scapula?

    <p>Serratus anterior</p> Signup and view all the answers

    What is the primary consequence of serratus anterior paralysis?

    <p>Winging scapula and potential impingement</p> Signup and view all the answers

    Which force couple contributes to scapular upward rotation?

    <p>Serratus anterior and upper trapezius</p> Signup and view all the answers

    Which muscles are primarily involved in shoulder flexion?

    <p>Anterior deltoid, coracobrachialis, and biceps brachii</p> Signup and view all the answers

    With paralysis of the deltoid muscle, what usually remains functional for arm abduction?

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

    What is typically a result of upper trapezius paralysis?

    <p>Moderate to marked difficulty elevating the arm</p> Signup and view all the answers

    During early phases of scapular upward rotation, where is the A/P axis primarily located?

    <p>Near the root of the scapula spine</p> Signup and view all the answers

    What role does the middle trapezius play in scapular motion?

    <p>It serves as a stabilizing synergist with serratus anterior</p> Signup and view all the answers

    What is one of the primary functions of the rotator cuff muscles during arm elevation?

    <p>Dynamic stability of the glenohumeral joint</p> Signup and view all the answers

    Which muscles are involved in the external rotation of the humerus?

    <p>Infraspinatus and teres minor</p> Signup and view all the answers

    How does the subscapularis muscle contribute during internal rotation of the humerus?

    <p>It increases active tension of the anterior capsule via capsular attachment.</p> Signup and view all the answers

    What effect do the rotator cuff muscles have on the glenohumeral joint during external rotation?

    <p>They increase active tension of the posterior GH capsule.</p> Signup and view all the answers

    What role does the supraspinatus play in shoulder abduction?

    <p>Facilitates superior roll of the humeral head</p> Signup and view all the answers

    What is the role of dynamic stability provided by the rotator cuff during arm elevation?

    <p>To maintain the position of the humeral head relative to the glenoid cavity</p> Signup and view all the answers

    Which muscles are primarily responsible for external rotation of the shoulder?

    <p>Infraspinatus and teres minor</p> Signup and view all the answers

    Which muscle is involved in the anterior roll during internal rotation of the shoulder?

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

    What is the function of the rhomboids during resisted adduction of the shoulder?

    <p>Counter upward rotation and abduction forces</p> Signup and view all the answers

    Which muscles contribute to both adduction and extension of the shoulder?

    <p>Posterior deltoid and triceps (long head)</p> Signup and view all the answers

    How do the infraspinatus and teres minor contribute during the external rotation of the shoulder?

    <p>Assisting with posterior roll of the humeral head</p> Signup and view all the answers

    What happens to the greater tubercle during external rotation?

    <p>Is cleared from the acromion process</p> Signup and view all the answers

    Which muscle group is involved in eccentrically controlling internal rotation?

    <p>Infraspinatus and teres minor</p> Signup and view all the answers

    Study Notes

    Shoulder Complex - Chapter 5

    • This chapter covers the anatomy and biomechanics of the shoulder complex, including the shoulder girdle, glenohumeral joint, acromioclavicular joint, and sternoclavicular joint.
    • The clavicle's long axis is positioned approximately 20 degrees posterior to the frontal plane.
    • The humeral head is situated approximately 30 degrees posteriorly relative to the medial-lateral axis through the elbow.
    • The scapula's plane of motion is called scaption, which combines abduction and flexion.
    • The sternoclavicular joint is a base joint (saddle, plane, modified ball and socket) that secures the clavicle, scapula, and upper extremity to the axial skeleton. It is characterized as having a high level of stability.
    • The sternoclavicular joint has an articular disc that divides the joint into medical and lateral cavities, which strengthens the articulation. Its main function is to absorb shock. The ligaments support the joint, notably the anterior and posterior sternoclavicular ligaments, and the interclavicular and costoclavicular ligaments. Stabilizing muscles include the sternocleidomastoid (anteriorly) sternothyroid (posteriorly), sternohyoid (posteriorly), and subclavius (inferiorly) muscles.
    • The degrees of freedom for the sternoclavicular joint is 3.
    • The acromioclavicular joint is a plane (gliding) joint with 3 degrees of freedom. It is composed of the clavicle and scapula.
    • The acromioclavicular joint's capsule is reinforced by superior and inferior acromioclavicular ligaments and the coracoclavicular ligament and an articular disc.
    • The muscles that stabilize the acromioclavicular joint include the deltoid, and trapezius muscles.

    Primary Movements of the Scapulothoracic Joint

    • The scapula moves in elevation/depression, protraction/retraction, and upward/downward rotation.

    Scapulothoracic Joint

    • It is not a true joint; it is the articulation between the anterior surface of the scapula and the posterior-lateral thorax; important for shoulder function.
    • The scapula is situated on ribs 2-7. The medial border of the scapula is approximately 6cm away from the spine.
    • The scapular muscles have a crucial role in shock absorption.
    • The stabilizing muscles of the scapulothoracic joint are the rhomboids, trapezius, and serratus anterior.

    Glenohumeral Joint

    • The Glenohumeral joint is a ball-and-socket type joint.
    • The glenoid fossa is positioned anterior-laterally and slightly upward by about 4 degrees.
    • The joint's capsule is made up of various ligaments that play a substantial role in maintaining structural stability.
    • The rotator cuff muscles (Supraspinatus, Infraspinatus, Teres minor, and subscapularis) provide dynamic stability during arm movements and control the arthrokinematics at the Glenohumeral joint.

    GH Joint Kinematics

    • The GH joint has 3 degrees of freedom (abduction, flexion/extension, internal/external rotation).
    • Abduction: The convex head of the humerus rolls superiorly and slides inferiorly.
    • Adduction: The head returns to neutral.
    • Flexion/Extension: The humeral head spins in the glenoid fossa.
    • Internal/External Rotation: Humeral head rolls, relative to the concave glenoid fossa.

    Coracoacromial Arch

    • The coracoacromial arch is formed by the coracoacromial ligament and the acromion process.
    • This area is important in limiting movement, and is a significant site for potential impingement in the shoulder.

    Overall Kinematics: Shoulder Abduction

    • Principles 1-6 describe the overall biomechanics of shoulder abduction.
    • Principle 1: 3:2:1 relationship of rotation between the shoulder, glenohumeral, and scapulothoracic joints.
    • Principle 2: A 60-degree combined range of motion occurs.
    • Principle 3: Clavicular retraction assists the acromioclavicular joint with optimal positioning within the frontal plane.
    • Principle 4: Scapular rotation adjustments (posterior tilt and external rotation) occur at the acromioclavicular joint and the sternoclavicular joints.
    • Principle 5: Clavicular elevation is halted by a strong coracoclavicular ligament, while the scapular upward rotators continue to drive the scapulothoracic upward motion.
    • Principle 6: GH joint external rotation (25-50 degrees) occurs primarily prior to shoulder abduction (70-80 degrees).

    Scapulo-Humeral Rhythm

    • Superior roll and compression of the humeral head, scapula upward rotation, and humeral ER are all important for smooth shoulder abduction motions.
    • The deltoid and rotator cuff muscles are essential for shoulder abduction motions.

    Muscle Interactions During Shoulder Abduction

    • Sequential activation of upper and lower trapezius, serratus anterior, supraspinatus, deltoid, infraspinatus, and teres minor muscles during shoulder abduction. This is a simultaneous interaction of all the supporting muscles.

    Muscle and Joint Interaction

    • Proximal stabilizers act on the spine, ribs, and cranium, while distal stabilizers act on the scapula, clavicle, and humerus (or forearm).

    Stabilizing Muscles

    • Each stabilizing muscle acts to elevate, depress, retract, or protract the shoulder components to prevent injury and facilitate smooth movement. This includes muscle groups like the upper trapezius, levator scapulae, rhomboids, lower trapezius, latissimus dorsi, pectoralis minor, and subclavius, and to assist with a range of motions of the glenohumeral joint.

    Serratus Anterior Weakness

    • Weakness in the serratus anterior muscle can cause the scapula to wing out, affecting shoulder stability and function.

    Rotator Cuff Muscles

    • These muscles (infraspinatus, teres minor, supraspinatus, subscapularis) provide dynamic stability to the Glenohumeral joint.
    • They're crucial to achieve active control in maintaining proper arthrokinematics during shoulder movements (abduction, external / internal rotation).

    Glenoid Labrum Tears, Shoulder Instability

    • Glenoid labrum tears can result from shoulder instability, often associated with repetitive motions, injuries, or an acute event. Pain and other symptoms often result.
    • Shoulder instability encompasses various disruptions in the structural stability of the shoulder, which can manifest as looseness or recurring subluxation or dislocations. This condition may also be caused by poor posture.

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    Shoulder Complex Chapter 5 PDF

    Description

    Test your knowledge on the anatomy and biomechanics of the shoulder complex. This quiz covers muscle functions, movement patterns, and joint mechanics related to shoulder movement. Perfect for anatomy students and fitness professionals.

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