16

Muscle Identification, Origin, Insertion, and Action: Groups 3-6

Topic #16

Chapter 11

Muscle Group #3: Muscles that Move the Pectoral Girdle (Scapula)

Overview of Muscles
  • Trapezius (Upper): Elevates the scapula.
  • Trapezius (Middle): Adducts the scapula.
  • Trapezius (Lower): Depresses and upwardly rotates the scapula.
  • Levator Scapulae: Elevates and downwardly rotates the scapula.
  • Rhomboids (Major and Minor): Elevate, adduct, and downwardly rotate the scapula.
  • Pectoralis Minor: Abducts and downwardly rotates the scapula.
  • Serratus Anterior: Abducts and upwardly rotates the scapula.
Actions of Muscles
  • All the actions cause movement of the scapula, requiring these muscles to have insertions on the scapula and origins on the axial skeleton as an anchor.
Individual Muscles

  • Levator Scapulae

    • Origin: Transverse processes of cervical vertebrae
    • Insertion: Superior medial border of scapula
    • Action: Elevation and downward rotation of scapula

  • Rhomboids (Major & Minor)

    • Origin: Cervical and thoracic spine
    • Insertion: Vertebral/medial border of scapula
    • Action: Elevation, adduction, and downward rotation of scapula

  • Trapezius

    • Origin: Occipital bone, cervical and thoracic spine
    • Insertion: Clavicle, acromion, and spine of scapula
    • Actions:
    • Elevate scapula
    • Depress scapula
    • Adduction of scapula
    • Upward rotation of scapula
    • Note: The trapezius has fibers running in different directions and can even be antagonistic to itself.

  • Pectoralis Minor

    • Origin: Ribs 3-5
    • Insertion: Coracoid process of scapula
    • Action: Abduction and downward rotation of scapula

  • Serratus Anterior

    • Origin: Ribs
    • Insertion: Vertebral border and inferior angle of scapula
    • Action: Abduction and upward rotation of scapula

Muscle Group #4: Muscles of the Thorax and Shoulder that Move the Humerus

Overview of Muscles
  • Pectoralis Major (PM): Flexion, adduction, and medial rotation.
  • Deltoid (PM): Flexion, extension, abduction, medial rotation, and lateral rotation.
  • Latissimus Dorsi (PM): Extension, adduction, and medial rotation.
  • Teres Major: Extension, adduction, and medial rotation.
  • Rotator Cuff Muscles (RC): Subscapularis, supraspinatus, infraspinatus, teres minor.
Muscle Actions

  • All insertions for these muscles are on the humerus at various points.

  • Common insertion points include:

    • Greater tubercle
    • Lesser tubercle
    • Intertubercular groove (bicipital groove)
    • Medial surface
    • Deltoid tuberosity

  • Note:

    • Muscles originating anterior to the shoulder joint facilitate flexion.
    • Muscles originating posterior to the shoulder joint facilitate extension.
Individual Muscles

  • Pectoralis Major

    • Origin: Clavicle, sternum, cartilage of upper ribs
    • Insertion: Intertubercular groove of humerus
    • Action: Flexion, adduction, and medial rotation at shoulder

  • Deltoid

    • Origin: Clavicle, acromion, spine of scapula
    • Insertion: Deltoid tuberosity of humerus
    • Action:
    • Flexion
    • Extension
    • Abduction
    • Medial rotation
    • Lateral rotation
    • Note: The deltoid is a composite muscle that is antagonistic to itself; it shares an origin with the trapezius.

  • Latissimus Dorsi

    • Origin: Thoracic and lumbar spine, iliac crest, last 4 ribs
    • Insertion: Intertubercular groove of humerus
    • Action: Extends, adducts, and medially rotates at shoulder.
    • Note: It serves as a prime mover in adduction and extension, significant in activities like rowing and swimming.

  • Teres Major

    • Origin: Inferior angle of scapula
    • Insertion: Intertubercular groove of humerus
    • Action: Extension, adduction, and medial rotation at shoulder
Rotator Cuff Muscles

  • Supraspinatus

    • Origin: Supraspinous fossa
    • Insertion: Greater tubercle of humerus
    • Action: Abduction at shoulder

  • Infraspinatus

    • Origin: Infraspinous fossa
    • Insertion: Greater tubercle
    • Action: Lateral rotation at shoulder

  • Teres Minor

    • Origin: Lateral border of scapula
    • Insertion: Greater tubercle of humerus
    • Action: Lateral rotation at shoulder

  • Subscapularis

    • Origin: Subscapular fossa
    • Insertion: Lesser tubercle of humerus
    • Action: Medial rotation at shoulder

  • Note: All medial rotators cross the shoulder joint anteriorly and insert on the lesser tubercle or intertubercular groove.

Muscle Group #5: Muscles of the Arm that Move the Radius and Ulna

Overview of Muscles
  • Triceps Brachii: Extensory action at elbow.
  • Brachialis: Flexes elbow.
  • Biceps Brachii: Flexes elbow and supinates forearm.
  • Brachioradialis: Flexes elbow.
  • Supinator: Supinates forearm.
  • Pronator Teres: Pronates forearm.
Elbow Joint Mechanics
  • Muscles that affect the elbow joint will have insertions on the ulna or radius; their origins are situated superior to the joint.
  • The joint between the humerus and ulna is a hinge joint, allowing only flexion and extension:
    • Muscles inserting on the ulna (e.g., triceps brachii, brachialis) cause flexion or extension.
  • The radius allows rotation, so muscles inserting on the radius can create supination or pronation.
  • Biceps brachii inserts on the radial tuberosity, facilitating both supination and flexion.
Individual Muscles

  • Triceps Brachii

    • Origin: Lateral border of scapula, posterior humerus
    • Insertion: Olecranon of ulna
    • Action: Extension at elbow

  • Brachialis

    • Origin: Anterior lower half of humerus
    • Insertion: Coronoid process of ulna
    • Action: Flexion at elbow

  • Biceps Brachii

    • Origin: Coracoid process of scapula and above glenoid cavity
    • Insertion: Radial tuberosity of radius
    • Action: Flexion at shoulder, flexion at elbow, and supination of forearm

  • Brachioradialis

    • Origin: Distal humerus
    • Insertion: Styloid process of radius
    • Action: Flexion at elbow

  • Supinator

    • Origin: Lateral epicondyle of humerus
    • Insertion: Lateral surface of radius
    • Action: Supination of forearm

  • Pronator Teres

    • Origin: Medial epicondyle of humerus
    • Insertion: Mid-lateral surface of radius
    • Action: Pronation of forearm

Muscle Group #6: Muscles of Forearm that Move the Wrist, Hand, Thumb and Digits

Overview of Flexors and Extensors
  • Flexors of the wrist are largely located on the anterior side of the forearm.
  • Extensors of the wrist are found mainly on the posterior side of the forearm.
  • Abduction of the wrist is facilitated by flexors and extensors on the lateral half of the forearm.
  • Adduction of the wrist is facilitated by flexors and extensors on the medial half of the forearm.
General Actions

  • Flexors:

    • Origin: Ulna, humerus, radius
    • Insertion: Metacarpals
    • Action: Flexion, abduction (lateral side), adduction (medial side) of wrist.
    • Note: Specific names of flexors and extensors are not required for identification.

  • Extensors:

    • Origin: Humerus, radius, and ulna
    • Insertion: Metacarpals, carpals, and phalanges
    • Action: Extension, abduction (lateral side), adduction (medial side) of wrist.
    • Note: Specific names of flexors and extensors are not required for identification.

Review Sections

  • Muscles of the Pectoral Girdle
  • Muscles that Move the Humerus
  • Muscles of the Arm
  • Muscles of the Forearm

Conclusion

  • Review lecture notes thoroughly.
  • Outline Topic 16 and focus on the questions provided for clarity before the next meeting.