Muscles of the Forelimb Anatomy
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Muscles of the Forelimb Anatomy

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Questions and Answers

Which part of the superficial pectoral runs cranially?

  • Transverse part
  • Deep part
  • Descending part (correct)
  • Ascending part

    • What is the primary action of the deep pectoral muscle?

  • Flexes the elbow
  • Lifts the scapula
  • Adducts and retracts the limb (correct)
  • Stabilizes the shoulder joint

    • What is the nerve supply for the rhomboideus muscle?

  • Long thoracic nerve
  • Accessory nerve
  • Dorsal branches of cervical and thoracic spinal nerves (correct)
  • Caudal pectoral nerve

    • Which action is primarily performed by the triceps brachii?

    <p>Extends the elbow</p> Signup and view all the answers

    Which of the following muscles is located deep to the trapezius?

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

    What is the origin of the anconeus muscle?

    <p>Distal humerus</p> Signup and view all the answers

    What action does the serratus ventralis perform?

    <p>Stabilizes the scapula</p> Signup and view all the answers

    Which intrinsic muscle of the forelimb is a shoulder extensor?

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

    Which nerve is responsible for supplying the extensor group of antebrachial muscles?

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

    Which of the following flexor muscles has three heads?

    <p>Deep digital flexor</p> Signup and view all the answers

    Which muscle is absent in carnivores but present in horses and goats?

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

    What is the primary action of the supinator muscle?

    <p>Supinates the paw</p> Signup and view all the answers

    What area does the cranial part of the deep pectoral lie in relation to the superficial pectoral?

    <p>Deep to it</p> Signup and view all the answers

    Which muscle specifically acts to flex the carpus?

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

    How does the pronator quadratus function in movement?

    <p>Pronation of the paw</p> Signup and view all the answers

    Which muscle can flex the digits as well as the carpus?

    <p>Superficial digital flexor</p> Signup and view all the answers

    Which muscle is primarily responsible for advancing and adducting the limb while also flexing the neck laterally?

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

    What is the insertion point of the Cleidobrachialis muscle?

    <p>Caudal border of the humerus</p> Signup and view all the answers

    Which nerve innervates the Latissimus dorsi muscle?

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

    What action is NOT performed by the Trapezius muscle?

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

    The Brachiocephalicus is divided into which two parts?

    <p>Cleidobrachialis and Cleidocephalicus</p> Signup and view all the answers

    What is the origin of the Omotransversarius muscle?

    <p>Wing of atlas (C1)</p> Signup and view all the answers

    Which of the following muscles is part of the deep group of extrinsic muscles of the forelimb?

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

    What is the primary action of the Latissimus dorsi muscle?

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

    Which muscles are innervated by the radial nerve?

    <p>Common digital extensor</p> Signup and view all the answers

    What is a common clinical sign of median nerve dysfunction in dogs?

    <p>Raised claws</p> Signup and view all the answers

    Which statement correctly describes the pathway of the median nerve?

    <p>Travels along the medial side of the forelimb</p> Signup and view all the answers

    Which muscle is primarily innervated by the thoracodorsal nerve?

    <p>Latissimus dorsi</p> Signup and view all the answers

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

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

    What reflex is associated with the lateral thoracic nerve?

    <p>Panniculus reflex</p> Signup and view all the answers

    How many spinal nerves are involved in the brachial plexus?

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

    Which branch of the pectoral nerve innervates the pectoral muscles?

    <p>Both cranial and caudal branches</p> Signup and view all the answers

    Which muscle is innervated by the suprascapular nerve?

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

    What is a primary action of the musculocutaneous nerve?

    <p>Flex the elbow joint</p> Signup and view all the answers

    The brachioradialis muscle primarily functions to:

    <p>Supinate the paw</p> Signup and view all the answers

    Which muscle is NOT supplied by the brachial plexus?

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

    Where does the suprascapular nerve travel?

    <p>Between supraspinatus and subscapularis</p> Signup and view all the answers

    The radial nerve is responsible for innervating which area?

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

    What condition may result from injury to the suprascapular nerve?

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

    The axillary nerve innervates which of the following muscles?

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

    Study Notes

    Muscles of the Forelimb

    • Muscles of the forelimb can be classified by their location as either extrinsic or intrinsic muscles.
    • Extrinsic muscles originate outside of the thoracic limb (e.g., cervical vertebrae), and insert on the thoracic limb (e.g., scapula or humerus).
    • Intrinsic muscles both originate and insert on the thoracic limb.
    • Extrinsic muscles can be further categorized into superficial and deep groups.

    Extrinsic Muscles

    • Superficial Group

      • Brachiocephalicus

        • Divided into Cleidobrachialis and Cleidocephalicus
        • Cleidobrachialis inserts on the cranial border of the humerus.
        • Cleidocephalicus further divides into Pars mastoidea, Pars cervicis, and Pars occipitalis.
        • Pars mastoidea inserts on the mastoid process of the skull.
        • Pars cervicis inserts on the neck.
        • Pars occipitalis inserts on the occipital bone of the skull.
        • Action: Lateral and ventral flexion of the head and neck, shoulder extension.
        • Innervation: Accessory and Axillary nerves.

      • Omotransversarius: Strap-like muscle adjacent to the Brachiocephalicus.

        • Originates on the wing of the atlas (C1).
        • Inserts on the distal scapular spine.
        • Action: Advances and adducts the limb, laterally flexes the neck.
        • Innervation: Accessory nerve.

      • Latissimus dorsi: Broad, flat, triangular muscle caudal to the scapula

        • Originates on the thoracolumbar fascia.
        • Inserts on the teres major tuberosity.
        • Action: Flexes the shoulder; advances the limb.
        • Innervation: Thoracodorsal nerve.

      • Trapezius: Broad, flat, triangular muscle caudal to the scapula.

        • Divided into Trapezius cervicis and Trapezius thoracis.
        • Originates from C2 to T10.
        • Inserts on the spine of the scapula.
        • Action: Elevates the shoulder, draws the scapula cranially and caudally.
        • Innervation: Accessory nerve.

      • Superficial Pectoral: Two parts - descending and transverse.

        • Originates on the cranial part of the sternum.
        • Inserts on the crest of the greater tubercle.
        • Action: Adducts and advances the limb.
        • Innervation: Cranial pectoral nerve

    • Deep Group

      • Deep Pectoral: Also called Pectoralis Profundus.

        • Has cranial and caudal parts.
        • Cranial part is deep to the superficial pectoral.
        • Caudal part is larger and called the ascending part.
        • Originates on the ventral part of the sternum.
        • Inserts on the greater and lesser tubercle of the humerus.
        • Action: Adducts the limb, retracts the limb, draws the trunk toward the limb.
        • Innervation: Caudal pectoral nerve and lateral thoracic nerve.

      • Rhomboideus: Three parts - Cervicis, Thoracis, and Capitis (canines and pigs only).

        • Located deep to the Trapezius.
        • Originates from C2 to T7 (Capitis from nuchal crest).
        • Inserts on the dorsal border of the scapula.
        • Action: Elevates the forelimb and draws the scapula against the trunk.
        • Innervation: Dorsal branches of cervical and thoracic spinal nerves.

      • Serratus Ventralis: Large, fan-shaped muscle with two parts - cervical and thoracic.

        • Originates on the transverse processes of C3-5 and Ribs 1-7 or 8.
        • Inserts on the serrated faces of the medial surface of the scapula (facies serrata).
        • Action: Protracts and stabilizes the scapula, helps with inspiration.
        • Innervation: Long thoracic nerve and ventral branches of cervical spinal nerves.

      • Subclavius: Absent in carnivores, present in horses and goats, smaller in oxen.

    Intrinsic Muscles

    • Intrinsic muscles of the forelimb can be categorized based on their location and action.

    Scapular Muscles

    • Scapular muscles act on the shoulder joint.

    • Lateral Muscles:

      • Supraspinatus: Occupies the supraspinous fossa (cranial).

        • Acts as the lateral collateral ligament of the shoulder joint for stabilization.
        • Action: Extends the shoulder.

      • Infraspinatus: Located in the infraspinous fossa (caudal).

        • Action: Externally rotates the shoulder.

    • Medial Muscles:

      • Subscapularis: Occupies the subscapular fossa (medial).

        • Action: Internally rotates the shoulder.

      • Coracobrachialis: Located between the subscapularis and biceps brachii.

        • Action: Adducts the shoulder.

    • Caudal Muscles:

      • Teres Major: Located caudal to the scapula, deep to the latissimus dorsi.

        • Action: Extends and adducts the shoulder.

      • Teres Minor: Located caudal to the scapula, lateral to the teres major.

        • Action: Externally rotates the shoulder.

      • Deltoideus: Located on the caudolateral aspect of the scapula.

        • Action: Abducts the shoulder.

    Antebrachial Muscles

    • Antebrachial muscles act on the carpal and digital joints.

    • Extensor Muscles (Craniolateral)

      • Extensor Carpi Radialis: Extends the carpus, Flexes the elbow.

      • Common Digital Extensor: Extends the carpus and digits.

      • Lateral Digital Extensor: Extends the carpus and lateral digits.

      • Ulnaris Lateralis: Flexes the carpus.

    • Flexor Muscles (Caudomedial)

      • Superficial Digital Flexor: Flexes the carpus and digits.

      • Deep Digital Flexor: Flexes the carpus and digits.

      • Flexor Carpi Radialis: Flexes the carpus.

      • Flexor Carpi Ulnaris: Flexes the carpus.

    • Pronator Muscles

      • Pronator Teres: Pronates the paw (turn paw downward).

      • Pronator Quadratus: Pronates the paw.

    • Supinator Muscles

      • Supinator: Supinates the paw (turn paw upward).

      • Brachioradialis: Supinates the paw.

    Nerves of the Forelimb

    • Brachial Plexus: Network of nerves formed by the ventral branches of the last three cervical and first two thoracic spinal nerves (C6,7,8 & T1,2).

    • Supplies all muscles of the forelimb except trapezius, omotransversarius, brachiocephalicus, rhomboideus, and the skin over the upper shoulder region.

    • Nerves originating from the brachial plexus:

      • Suprascapular Nerve
      • Subscapular Nerve
      • Musculocutaneous Nerve
      • Axillary Nerve
      • Lateral Thoracic Nerve
      • Radial Nerve
      • Median Nerve
      • Ulnar Nerve
      • Thoracodorsal Nerve
      • Pectoral Nerves
      • Long Thoracic Nerve

    • Suprascapular Nerve (C6, C7)

      • Innervates Supraspinatus and Infraspinatus muscles.
      • Muscles actions: Stabilizes and extends the shoulder joint.
      • CLINICAL: Susceptible to injury due to over abduction or violent retraction, causing Shoulder Slip/Sweeney.

    • Subscapular Nerve (C6, C7)

      • Innervates Subscapularis muscle.
      • Muscle action: Adducts the limb and rotates the humerus medially.
      • Also, a branch of the Subscapular Nerve, known as the Thoracodorsal Nerve (C8) innervates the Latissimus Dorsi.

    • Musculocutaneous Nerve (C6, C7, C8)

      • Innervates Biceps Brachii, Brachialis, and Coracobrachialis muscles.
      • Muscles actions: Shoulder extensors and elbow flexors.
      • CLINICAL: Dysfunction of musculocutaneous nerve in dogs may cause little change in gait due to redundancy but may make it difficult to offer a paw.

    • Axillary Nerve (C7, C8)

      • Innervates Deltoideus, Teres major, Teres minor, and part of the Subscapularis muscles.
      • Muscles actions: Flexors of the shoulder joint; Rotates the brachium.

    • Radial Nerve (C7, C8, T1, T2)

      • Innervates Extensors of carpus and digits (Extensor carpi radialis, Common digital extensor, Lateral digital extensor), and Triceps Brachii muscle (elbow extension).
      • CLINICAL:
        • High Radial Nerve Paralysis (more common): Damage occurs proximal to the middle of the arm.
        • Low Radial Nerve Paralysis: Damage occurs distal to the triceps brachii innervation site.

    • Median Nerve (C8, T1, T2):

      • Innervates most flexors of the carpus and digits (Flexor carpi radialis, Superficial digital flexor, Pronator teres, Pronator quadratus, and the humeral, radial, and ulnar heads of the Deep digital flexor).
      • CLINICAL: Dysfunction of median nerve in dogs can cause carpus extension and “raised claws”.

    • Ulnar Nerve (C8, T1, T2)

      • Innervates Flexor carpi ulnaris, interosseous muscles, and provides sensory innervation to the caudal forelimb and lateral digits.
        • Dorsal branch: Supplies skin on the lateral aspect of the forefoot.
        • Palmar branch: Supplies interosseous and other small muscles of the foot, and supplies sensory branches to skin and deep structures.

    • Lateral Thoracic Nerve (C8, T1):

      • Innervates the Cutaneous Trunci muscle and provides sensory innervation to the ventral part of the thorax and abdomen.
      • Muscle action: Panniculus reflex
      • CLINICAL: Sensory function in the lateral thorax is important for assessing for nerve damage.

    • Long Thoracic Nerve:

      • Innervates the Serratus Ventralis muscle.

    • Pectoral Nerves (C6-T1):

      • Innervates the superficial and deep pectoral muscles, including the subclavius muscle.
      • Muscle action: Adducts the limb.

    • Additional Notes on the Brachial Plexus:

      • Number of Spinal Nerves: While mammals have 7 cervical vertebrae, they also possess 8 cervical spinal nerves, with one nerve traveling with each vertebra in the cervical region and the 8th nerve traveling with the first rib.
      • Important Note: The specific nerve supply to muscles may vary slightly between different species.

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    Forelimb Muscles PDF

    Description

    Explore the classification and anatomy of the forelimb muscles. This quiz covers the differences between extrinsic and intrinsic muscles, with a focus on the superficial extrinsic group, including the brachiocephalicus and its parts. Test your knowledge on muscle origins, insertions, and actions.

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