Nerve Supply to the Thoracic Limb Flashcards
What is the brachial plexus formed by?
the ventral branches of spinal nerves C6-T1
What are the nerves emerging from the brachial plexus arranged around?
the axillary artery
What do the most cranial nerves in the brachial plexus receive contribution from?
the most cranial spinal cord segments and the corresponding dorsal root ganglion
What do the most caudal nerves in the brachial plexus receive contribution from?
caudal segments of the spinal cord and dorsal root ganglion
What type of fibers are in the nerves of the brachial plexus?
motor (GSE) and sensory (GSA)
What do the sensory fibers of the nerves in the brachial plexus supply?
convey sensory information form the muscle spindles within the skeletal muscles, other mechanoreceptors in the tendons, ligaments, and joint capsule, and the skin
What do the motor fibers of the nerves in the brachial plexus supply?
the skeletal muscle, and facilitate their contraction which causes movement at the joint and the limb as a whole
What are the roots of the cleidobrachial nerve?
C6 and C7
What does the cleidobrachial nerve supply?
the cleidobrachialis muscle
What are the roots of the deep pectoral nerves?
C6-C8
What do the deep pectoral nerves supply?
the pectoralis ascendens
What are the roots of the thoracodorsal nerve?
C6-T1
What does the thoracodorsal nerve innervate?
the latissimus dorsi
What are the roots of the long thoracic nerve?
C8-T1
What does the long thoracic nerve supply?
serratus ventralis thoracis
What are the roots of the lateral thoracic nerve?
C8-T1
What does the lateral thoracic nerve supply?
GSE fibers to the muscular axillary arch, the cutaneous trunci and the cranial preputial muscles
True or False: the lateral thoracic nerve has cutaneous sensory fibers
false; the fibers come from T3-L3 spinal nerves
What are the possibilities that the extrinsic muscles of the thoracic limb are innervated by?
nerves from the brachial plexus, accessory nerve, or segmental cervical and or thoracic spinal nerves
What extrinsic muscles of the thoracic limb are innervated by nerves from the brachial plexus?
pectorals, latissimus dorsi, and serratus ventralis thoracis
What extrinsic muscles of the thoracic limb are innervated by the segmental spinal nerves?
the rhomboideus and serratus cervicis
What extrinsic muscles of the thoracic limb are innervated by the accessory nerve?
the trapezius and omotransversarius
What supplies the cleidocervicalis and the distal part of the brachiocephalicus?
the accessory nerve along with the segmental cervical nerves
What are the intrinsic muscles supplied by?
the branches of the brachial plexus
What are the roots of the axillary nerve?
C6-C8
What does the axillary nerve supply?
the primary flexors of the shoulder joint and the skin of the cranial and lateral aspect of the shoulder and brachium
What are the primary flexors of the shoulder joint?
the teres major, teres minor, and the deltoideus
Where does the axillary nerve course?
in between the teres major and the subscapularis
What does injury to the axillary nerve cause?
lack of cutaneous sensation on the lateral aspect of the shoulder region and the craniolateral aspect of the upper brachial region and atrophy of the teres major, teres minor, and deltoideus
Why does injury to the axillary nerve have no impact on the shoulder joint flexion?
the latissimus dorsi and the long head of triceps compensate for the motor function
What reflex test can be used to test for axillary nerve damage?
a pinprick test in the autonomous zone
How do the latissimus dorsi and the long head of triceps flex the shoulder?
the latissimus dorsi pulls the humerus caudally and the long head of triceps pulls the scapula ventrally
What does the subscapular nerve supply?
the subscapularis
Where does the cranial lateral cutaneous brachial nerve course?
it emerges caudal to the shoulder joint on the lateral side of the limb at the distal edge of the deltoideus muscle
What does the cranial lateral cutaneous brachial nerve innervate?
the skin on the lateral brachial region and caudal scapular area
What does the descending branch of the cranial lateral cutaneous brachial nerve join?
the medial branch of the superficial radial nerve to form the cranial cutaneous antebrachial nerve
What are the roots of the suprascapular nerve?
C6-C7
Where does the suprascapular nerve course?
between the subscapularis and the supraspinatus muscle, and passes cranial to the edge of the scapular notch
What does the suprascapular nerve supply?
the primary extensors of the shoulder joint
What are the primary extensors of the shoulder joint
the supraspinatus and the infraspinatus
What can cause injury to the suprascapular nerve?
a fracture at the neck of the scapula