Thoracic Nerves (Small Animal) Quiz
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Questions and Answers

Which nerve provides somatic motor innervation to the coracobrachialis muscle, biceps brachii muscle, and brachialis muscle?

  • Suprascapular nerve
  • Subscapular nerve
  • Thoracodorsal nerve
  • Musculocutaneous nerve (correct)

    • What type of innervation is provided to the forelimb by the brachial plexus?

  • Sensory afferent only
  • Motor efferent only
  • Mixed with sensory afferent and motor efferent (correct)
  • None of the above

    • Which nerve runs with the lateral thoracic artery and targets the motor neuron to the cutaneous trunci muscle?

  • Thoracodorsal nerve
  • Cranial pectoral nerve
  • Lateral thoracic nerve (correct)
  • Caudal pectoral nerve

    • What is the function provided by the musculocutaneous nerve?

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

    Which spinal nerves form the brachial plexus?

    <p>C6-T2</p> Signup and view all the answers

    Which nerve provides sensory innervation to the dorsal manus?

    <p>Lateral cutaneous antebrachial nerve</p> Signup and view all the answers

    Which nerve targets the subscapularis muscle?

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

    What is the effect of axillary nerve damage on the brachium?

    <p>Loss of sensation on the lateral aspect</p> Signup and view all the answers

    Which nerve targets the latissimus dorsi muscle?

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

    Which vein gives off a medially directed branch known as the Medial cubital vein?

    <p>Cephalic vein</p> Signup and view all the answers

    Which nerve is protected by the acromion of the scapula?

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

    Which nerve provides motor innervation to the anconeus muscle?

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

    Which nerve is in contact with the caudal surface of the brachial artery?

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

    Which nerve provides sensory innervation to the palmar aspect of the antebrachium?

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

    Which muscle does the axillary nerve NOT provide motor innervation to?

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

    Which muscles receive sensory innervation from the median nerve?

    <p>Pronator teres, pronator quadratus, and flexor carpi radialis</p> Signup and view all the answers

    Which nerve provides sensory innervation to the medial aspect of the antebrachium?

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

    What is the main function of the deep branch of the radial nerve?

    <p>Providing motor innervation to the extensors of the carpus and digits</p> Signup and view all the answers

    What is the name of the nerve that enters the space between the subscapularis muscle and the teres major muscle?

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

    Damage to the median and ulnar nerve decreases the ability to do which of the following?

    <p>Flex the carpus and digits</p> Signup and view all the answers

    What is the term for an area of sensation that is provided by only one nerve without overlap from adjacent nerves?

    <p>Autonomous zone</p> Signup and view all the answers

    Which nerve is necessary for weight bearing?

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

    Which nerve damage is specifically linked to the loss of cutaneous sensation to the lateral aspect of the 5th digit?

    <p>Ulnar nerve damage</p> Signup and view all the answers

    What is the effect of axillary nerve damage on the shoulder?

    <p>Drooping of the shoulder</p> Signup and view all the answers

    Musculocutaneous nerve damage would result in the decreased ability to do which of the following?

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

    Which nerve is associated with the 'funny bone'?

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

    Which digit is an autonomous zone for the ulnar nerve?

    <p>5th digit</p> Signup and view all the answers

    What is the effect of distal radial nerve injury on the antebrachium?

    <p>Loss of cutaneous sensation on the cranial aspect</p> Signup and view all the answers

    Which ability can be lost in a patient with a proximal radial nerve injury?

    <p>Ability to support their weight on that forelimb</p> Signup and view all the answers

    What is the effect of damage to the median and ulnar nerves?

    <p>Sinking (hyperextension) of the carpus</p> Signup and view all the answers

    What is the relationship between the median nerve and the medial epicondyle of the humerus?

    <p>The median nerve is immediately cranial to the medial epicondyle of the humerus.</p> Signup and view all the answers

    Which nerve provides motor innervation to the flexor carpi ulnaris muscle?

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

    Study Notes

    Brachial Plexus

    • Composed of ventral branches of spinal nerves from C6-T2
    • Innervation to the forelimb is mixed with sensory afferent and motor efferent
    • Located in the axillary region

    Proximal Nerves of the Forelimb

    • Cranial pectoral nerve:
      • Runs with the external thoracic artery
      • Targets the superficial pectoral muscle
    • Caudal pectoral nerve:
      • Targets the deep pectoral muscle
    • Lateral thoracic nerve:
      • Runs with the lateral thoracic artery, near the axillary lymph node
      • Targets the motor neuron to the cutaneous trunci muscle, involved in the panniculus reflex
    • Thoracodorsal nerve:
      • Runs with the thoracodorsal artery
      • Targets the latissimus dorsi muscle

    Nerves of the Forelimb

    • Suprascapular nerve:
      • Travels laterally between the subscapularis muscle and the supraspinatus muscle
      • Targets the infraspinatus muscle and supraspinatus muscle
      • Protected by the acromion of the scapula
    • Subscapular nerve:
      • May have multiple visible branches
      • Targets the subscapularis muscle
    • Musculocutaneous nerve:
      • Provides somatic motor innervation to the coracobrachialis muscle, biceps brachii muscle, and brachialis muscle
      • Provides sensory to the medial aspect of the antebrachium via the medial cutaneous antebrachial nerve
      • Motor function is elbow flexion
    • Axillary nerve:
      • Enters the space between the subscapularis muscle and the teres major muscle
      • Provides somatic motor innervation to the teres major muscle, teres minor muscle, deltoideus muscle, and part of the subscapularis muscle
      • Provides sensory to the caudal scapular region and craniolateral brachium
    • Radial nerve:
      • Enters the triceps brachii muscle between the long head and medial head
      • Spirals caudally around the humerus and emerges laterally between the triceps brachii muscle and the brachialis muscle
      • Provides somatic motor innervation to the triceps brachii muscle, tensor fascia antebrachii muscle, and anconeus muscle
      • Necessary for weight bearing
      • Deep branch provides somatic motor innervation to the extensors of the carpus and digits
      • Superficial branch (lateral cutaneous antebrachial nerve) provides sensory innervation to the dorsal manus
    • Median nerve:
      • Both the median nerve and the ulnar nerve start as a common trunk
      • Provides sensory innervation to the palmar aspect of the manus
      • Targets and provides sensory innervation to the pronator teres muscle, pronator quadratus muscle, flexor carpi radialis muscle, superficial digital flexor muscle, and deep digital flexor muscle
      • Continues distally with the median artery through the carpal canal
    • Ulnar nerve:
      • In contact with the collateral ulnar artery and runs towards the caudal aspect of the elbow
      • Lateral to the medial epicondyle of the humerus
      • Provides somatic motor innervation to the flexor carpi ulnaris muscle and deep digital flexor muscle
      • Provides sensory innervation to the palmar aspect of the antebrachium and palmar aspect of the manus

    Autonomous Zones

    • An autonomous zone refers to an area of sensation provided by only one nerve without overlap from adjacent nerves
    • Examples of autonomous zones include:
      • Sensory innervation to the 5th digit, which is an autonomous zone for the ulnar nerve
      • Most areas of the skin are innervated by multiple nerves
      • Nerves supplying autonomous zones in the forelimb include the ulnar nerve, radial nerve, and musculocutaneous nerve

    Radial Nerve Damage

    • Proximal injury:
      • Results in loss of ability to extend the elbow, carpus, or digits
      • Causes loss of ability to support weight on that forelimb
      • Refers to damage occurring at the brachial plexus prior to innervation to the triceps muscle
    • Distal injury:
      • Refers to damage occurring after innervation to the triceps muscle
      • Results in loss of cutaneous sensation (superficial branch) on the cranial aspect of the antebrachium and the dorsal aspect of the paw

    Median and Ulnar Nerve Damage

    • Results in:
      • Reduction or complete loss of the ability to flex the carpus and digits
      • Sinking (hyperextension) of the carpus and fetlock
      • Loss of sensation to the palmar aspect of the paw
      • Loss of cutaneous sensation to the lateral aspect of the 5th digit specifically linked to ulnar nerve damage

    Axillary Nerve Damage

    • Results in:
      • Loss of motor innervation to the flexors of the shoulder (deltoideus, teres major, teres minor, and part of the subscapularis muscle), causing a "dropped shoulder" appearance
      • Loss of sensation to the lateral aspect of the brachium and caudal scapular region

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    2- Thoracic Nerves (Small Animal).docx

    Description

    This quiz covers the structure and function of the brachial plexus, including its composition, location, and innervation. It also touches on the cranial pectoral nerve and its targets.

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