Anatomy of Shoulder Muscles
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Questions and Answers

Which muscle is not part of the superficial group of extrinsic forelimb muscles?

  • Brachiocephalicus
  • Latissimus dorsi
  • Trapezius
  • Rhomboideus (correct)

    • Which muscle originates from the wing of atlas C1?

  • Omotransversarius (correct)
  • Brachiocephalicus
  • Latissimus dorsi
  • Trapezius

    • What is the action of the Latissimus dorsi muscle?

  • Elevates the shoulder
  • Flexes the shoulder and advances the limb (correct)
  • Extends the neck
  • Adducts the limb

    • Which part of the Brachiocephalicus inserts at the mastoid process of the skull?

    <p>Pars mastoidea</p> Signup and view all the answers

    The trapezius muscle has its origins at which vertebrae?

    <p>C2 to T10</p> Signup and view all the answers

    What nerve supplies the action of the Trapezius muscle?

    <p>Accessory nerve</p> Signup and view all the answers

    Which muscle is responsible for lateral and ventral flexion of the head and neck?

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

    What is the innervation of the Latissimus dorsi muscle?

    <p>Thoracodorsal nerve</p> Signup and view all the answers

    Which muscle acts as a medial collateral ligament to stabilize the shoulder joint?

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

    What is the primary action of the Infraspinatus muscle?

    <p>Flexes, stabilizes and abducts the shoulder</p> Signup and view all the answers

    Which nerve innervates the Teres major muscle?

    <p>Axillary nerve</p> Signup and view all the answers

    Where does the Biceps brachii muscle originate?

    <p>Supraglenoid tubercle</p> Signup and view all the answers

    What is the primary function of the Triceps brachii muscle?

    <p>EXTENSOR of the elbow</p> Signup and view all the answers

    Which muscle originates from the coracoid process?

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

    The Tensor fasciae antebrachii muscle primarily functions as which type of muscle?

    <p>EXTENSOR of the elbow</p> Signup and view all the answers

    Which muscle's action includes flexion and stabilization of the shoulder?

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

    Which muscle is primarily responsible for supinating the paw?

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

    What is a potential consequence of injury to the suprascapular nerve?

    <p>Shoulder slip or Sweeney</p> Signup and view all the answers

    Which muscle does the musculocutaneous nerve NOT supply?

    <p>Triceps brachii</p> Signup and view all the answers

    Which nerve is responsible for innervating the shoulder flexors and rotators?

    <p>Axillary nerve</p> Signup and view all the answers

    Which muscles participate in the action of elbow flexion?

    <p>Biceps brachii and brachialis</p> Signup and view all the answers

    Which of the following conditions does NOT affect the brachial plexus directly?

    <p>Compression of the radial nerve</p> Signup and view all the answers

    The radial nerve wraps around which part of the limb?

    <p>Lateral side of the limb</p> Signup and view all the answers

    Which muscle action is primarily associated with the action of the subscapularis muscle?

    <p>Medial rotation of the humerus</p> Signup and view all the answers

    What is the primary action of the superficial pectoral muscle?

    <p>Adducts and advances the limb</p> Signup and view all the answers

    Which part of the deep pectoral muscle is also referred to as the ascending part?

    <p>Caudal part</p> Signup and view all the answers

    What is the origin of the rhomboideus muscle?

    <p>C2 to T7 vertebrae</p> Signup and view all the answers

    Which nerve innervates the serratus ventralis muscle?

    <p>Long thoracic nerve</p> Signup and view all the answers

    Which muscle acts primarily as a shoulder extensor?

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

    What distinguishes the intrinsic muscles of the thoracic limb from other muscle groups?

    <p>They insert on the thoracic limb</p> Signup and view all the answers

    What is the function of the subclavius muscle in mammals?

    <p>Absent in carnivores</p> Signup and view all the answers

    What is the primary function of the triceps brachii muscle?

    <p>Elbow extension</p> Signup and view all the answers

    The deep pectoral muscle is also known as what?

    <p>Pectoralis profundus</p> Signup and view all the answers

    Which of the following muscles is NOT innervated by the median nerve?

    <p>Flexor carpi ulnaris</p> Signup and view all the answers

    What symptom is associated with dysfunction of the median nerve in dogs?

    <p>Carpus extension ('Raised Claws')</p> Signup and view all the answers

    Which nerve innervates the latissimus dorsi muscle?

    <p>Thoracodorsal nerve</p> Signup and view all the answers

    Which nerve provides sensory innervation to the palmar surface of the paw?

    <p>Median nerve</p> Signup and view all the answers

    How many spinal nerves make up the brachial plexus?

    <p>8</p> Signup and view all the answers

    Which muscle is innervated by the lateral thoracic nerve?

    <p>Cutaneous trunci</p> Signup and view all the answers

    What is the primary action of the pectoral muscles?

    <p>Adducting the limb</p> Signup and view all the answers

    Study Notes

    Shoulder Muscles

    • Origin: supraspinous fossa
    • Insertion: Greater tubercle
    • Action: Extends and stabilizes the shoulder
    • Nerve: Suprascapular n.

    Infraspinatus

    • Origin: infraspinous fossa
    • Insertion: Greater tubercle
    • Action: Flexes, stabilizes and abducts the shoulder
    • Nerve: Suprascapular n.

    Subscapularis

    • Origin: subscapular fossa
    • Insertion: Lesser tubercle
    • Action: Extends, adducts and stabilizes the shoulder
    • Nerve: Subscapular n.

    Coracobrachialis

    • Origin: coracoid process
    • Insertion: lesser tubercle
    • Action: flexes and abducts the shoulder
    • Nerve: Musculocutaneous n.

    Deltoideus

    • Origin: spine of scapula and acromion process
    • Insertion: Deltoid tuberosity
    • Action: flexes the shoulder
    • Nerve: Axillary n.

    Teres Major and Teres Minor

    • Origin: Caudal border of scapula
    • Insertion: Teres major and minor tuberosities
    • Action: flexes the shoulder
    • Nerve: Axillary n.

    Brachial Muscles

    • Action: Act on the elbow joint

    Flexor Muscles

    • Lateral Muscles
      • Biceps brachii
        • Origin: Supraglenoid tubercle
        • Insertion: Radial tuberosity
        • Action: flexes the elbow
        • Nerve: Musculocutaneous n.
      • Brachialis
        • Origin: Caudolateral surface of proximal humerus
        • Insertion: Radial tuberosity
        • Action: flexes the elbow
        • Nerve: Musculocutaneous n.
    • Extensor Muscles
      • Triceps brachii
        • Origin: Humerus (except the long head)
        • Insertion: Olecranon
        • Action: extends the elbow
        • Nerve: Radial n.
      • Tensor fasciae antebrachii
        • Action: Extends the elbow
        • Nerve: Radial n.

    Extrinsic Muscles of the Forelimb

    • Originate: outside of the thoracic limb
    • Insert: on the thoracic limb
    • 2 Groups
      • Superficial Group
        • Brachiocephalicus
        • Omotransversarius
        • Latissimus dorsi
        • Trapezius
        • Superficial Pectoral
      • Deep Group
        • Rhomboideus
        • Deltoideus
        • Deep Pectoral

    Brachiocephalicus

    • Action: lateral and ventral flexion of head & neck; extends shoulder
    • Innervation: Accessory + Axillary n

    Omotransversarius

    • Action: advance and adduct limb; flexes neck laterally
    • Nerve: Accessory n.

    Latissimus dorsi

    • Action: Flexes shoulder; advances limb
    • Nerve: Thoracodorsal n.

    Trapezius

    • Action: elevates shoulder, draws scapula cranially and caudally
    • Nerve: Accessory n.

    Superficial Pectoral

    • Action: adducts and advances the limb
    • Nerve: Cr.pectoral n.

    Deep Pectoral

    • Action: adducts limb, retracts limb, draws trunk toward the limb
    • Nerve: Caudal pectoral n.+ lateral thoracic n.

    Rhomboideus

    • Origin: C2 to T7 (capitis from nuchal crest)
    • Insertion: dorsal border of scapula
    • Action: elevates forelimb and draws scapula against the trunk
    • Nerve: dorsal branches of cervical and thoracic spinal nerves

    Serratus ventralis

    • Action:
    • Nerve: Long thoracic n.+ ventral branches of cervical spinal nerves

    Subclavius m.

    • Present: Horse and goat
    • Absent: Carnivores

    Intrinsic Muscles of the Forelimb

    • Originate and insert: on the thoracic limb

    Scapular Muscles

    • Action: Act on the shoulder joint

    Lateral Scapular Muscles

    - Supraspinatus
    - **Action:** Extends the shoulder
    - **Nerve:** Suprascapular n.
- Infraspinatus
    - **Nerve:** Suprascapular n.

    Medial Scapular Muscles

    - Subscapularis
    - **Nerve:** Subscapular n.
- Coracobrachialis
    - **Nerve:** Musculocutaneous n.

    Caudal Scapular Muscles

    - Teres major and minor
    - **Nerve:** Axillary n.
- Deltoideus 
    - **Nerve:** Axillary n.

    Brachial Plexus

    • Formed By: ventral branch of last three cervical and first two thoracic spinal nerves (C6,7,8 &T1,2)
    • Innervates: all muscles of forelimb except
      • Trapezius
      • Omotransversarius
      • Brachiocephalicus
      • Rhomboideus
      • Skin over upper shoulder region

    Nerves of the Forelimb

    • Suprascapular n. (C6, C7)
      • Muscles:
        • Supraspinatus m.
        • Infraspinatus m.
      • Action: Stabilization and extension of the shoulder joint.
    • Subscapular n. (C6, C7)
      • Muscles: Subscapularis m.
      • Action: Adducts the limb and rotates humerus medially.
    • Musculocutaneous n. (C6, C7, C8)
      • Muscles:
        • biceps brachii m.
        • brachialis m.
        • coracobrachialis m.
      • Action: Shoulder extensors and Elbow flexors
    • Axillary n. (C7,C8)
      • Muscles:
        • Deltoideus m.
        • Teres major m.
        • Teres minor m.
        • Part of the subscapularis m.
      • Action: Flexors of the shoulder joint; Rotates brachium.
    • Radial n. (C7, C8, T1, T2)
      • Muscles:
        • Extensors of carpus and digits
        • extensor carpi radialis
        • common digital extensor
        • lateral digital extensor
        • Triceps brachii m. (elbow extension)
    • Median n. (C8.T1, T2)
      • Muscles:
        • Flexor carpi radialis m.
        • superficial digital flexor m.
        • pronator teres
        • pronator quadratus
        • deep digital flexor m.
      • Action: most FLEXORS OF CARPUS AND DIGITS
    • Ulnar n. (C8, T1, T2)
      • Muscles:
        • Flexor carpi ulnaris m.
        • Interosseous m.
    • Thoracodorsal n. (C8)
      • Muscles: Latissimus dorsi m.
      • Action: Retracts the limb.
    • Lateral thoracic n. (C8, T1)
      • Action of m.: Panniculus reflex - skin twitching
    • Long Thoracic n.
      • Muscles: Serratus ventralis
    • Pectoral n. (C6-T1)
      • Muscles: superficial and deep pectoral m. including subclavius
      • Action: adduct the limb

    Miscellaneous

    • Why does the brachial plexus have 8 spinal nerves? All mammals have 7 cervical vertebrae, but the brachial plexus is formed by the ventral branch of the last three cervical and first two thoracic spinal nerves, resulting in a total of 8 nerves.
    • Supinators
      • Action: Supinates paw (turn paw upward)
      • Nerve: Radial n.
      • Muscles:
        • Supinator
        • Brachioradialis

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    Description

    This quiz assesses your knowledge of the anatomy, origins, insertions, actions, and innervation of the shoulder muscles. Test your understanding of muscles like the Infraspinatus, Subscapularis, and Deltoideus and how they contribute to shoulder movement and stability.

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