Prac 2 Brachial Plexus Practical Notes 2024 PDF

Gross Anatomy – Practical 2 Brachial Plexus - Innervation of the Forelimb Pre-reading / viewing: Canine Brachial Plexus Practical class power point 60 min Learning Objectives: Identify the major nerves of the brachial plexus and the fore...

Gross Anatomy – Practical 2 Brachial Plexus - Innervation of the Forelimb Pre-reading / viewing: Canine Brachial Plexus Practical class power point 60 min Learning Objectives: Identify the major nerves of the brachial plexus and the forelimb: including radial n., ulnar n., median n. Describe the anatomical relationship and function of the brachial plexus. Describe the anatomical relationship and function of the major and clinically relevant nerves of the forelimb. Reference material: Millers and Evans, 2020. Miller’s Anatomy of the Dog 5th ed. Saunders. The Spinal nerves: pp. 704 -755 Evans and de Lahunta. 2010. Guide to the Dissection of the Dog 7th ed. Saunders. Videos: Singh, 2018, Dyce, Sack and Wensing’s Textbook of Veterinary Anatomy 5th ed. Saunders. The nervous system: pp. 253-317 The forelimb of the dog and cat: pp. 462- 480. Clinical relevance: The brachial plexus and nerves arising from it are responsible for cutaneous and muscular innervation of the entire forelimb. Knowledge about the brachial plexus and nerves of the forelimb are of surgical importance as well as for post traumatic evaluation, especially radial avulsion causing paralysis. 1  Dissection Instruction: CAREFULLY do the following dissection. The best instrument for most of this part of the dissection is a blunt probe. ➔ Abduct the LEFT forelimb and transect the deep and superficial pectoral muscles to expose the axillary regions for dissection of the vessels and nerves. Once the mm. pectoralis are transected, abduct the limb to expose the neurovascular elements in the axilla. You will need to carefully break down the strands of fascia bridging between the limb and the thoracic wall. ➔ Transect the muscles around the shoulder blade and adduct it laterally to expose the brachial plexus. Rotate and reflect the attached limb to visualise the relationship between the central nerve roots and their peripheral nerves. You may not be able to identify individual nerves, but this approach allows you to appreciate the complexity and location of the brachial plexus. ➔ Remove the entire forelimb from the body by dissecting the remaining muscles, nerves and blood vessels as close as possible to the body wall. Diagram: Brachial plexus, medial aspect common Diagram: Brachial plexus, medial aspect common spinal root origin of nerves from the plexus. spinal root origin of nerves from the plexus. 2 Images from Miller’s Anatomy of the Dog 5th Ed., 2020 pp. 713 On the median aspect of the brachium: IDENTIFY: Suprascapular nerve. This nerve enters between the mm. supraspinatus and subscapularis from the medial side. It is accompanied by the suprascapular artery and vein. The motor and sensory functions of this nerve are: Subscapular nerve. The motor and sensory functions of this nerve are: Musculocutaneous nerve. This nerve lies between the m. biceps brachii and the brachial vessels on the median aspect of the limb. ➔ Trace the musculocutaneous n. into the muscle bellies it innervates mm. coracobrachialis, biceps brachii, brachialis in the proximal antebrachium. The motor and sensory functions of this nerve are: Axillary nerve. This nerve courses between the m. subscapularis and m. teres major at the level of the scapular neck. The motor and sensory functions of this nerve are: 3  Radial nerve. Largest nerve of the brachial plexus. Enters the medial side of the brachium distal to the shoulder joint, passes between the heads of the triceps brachii mm, sends branches to all four heads of the triceps. Spirals caudally around the humerus, travels laterally to divide cranially into a deep and superficial branch. The superficial branch (sensory) emerges on the cranial surface of the antebrachium, divides into lateral and medial branches, follows the cephalic v. to the carpus and dorsal surface of the paw. The deep branch (motor) supplies the cranial antebrachial muscles. ➔Trace the radial n. as far as possible (median and lateral aspect of the limb) The motor and sensory functions of this nerve are: Ulnar nerve. Identify the ulnar n. at the elbow joint where it crosses the medial epicondyle of the humerus caudally to enter the antebrachium. ➔ On the medial aspect of the forelimb trace the ulnar n. into the muscle bellies it innervates in the proximal antebrachium: mm. ulnar head deep digital flexor, flexor carpi ulnaris. The motor and sensory functions of this nerve are: ➔ branch: Caudal cutaneous antebrachial n leaves the caudal part of the ulnar nerve to pass over the medial surface of the olecranon into the antebrachium. Site for testing avulsion of brachial nerve roots T1-2. The motor and sensory functions of this nerve are: ➔ Trace the ulnar nerve back proximally to the common trunk with the median nerve. Common trunk median and ulnar n. Once you have identified the common trunk (median and ulnar n.), follow the median n. distally. The sensory functions of this nerve are: 4 O Median nerve. ➔ On the medial aspect of the forelimb: trace the median n. into the muscle bellies it innervates in the proximal antebrachium: mm. pronator quadratus, pronator teres, radial and humeral head of deep digital flexor, superficial digital flexor, flexor carpi radialis, skin of caudal antebrachium. The motor and sensory functions of this nerve are: Fore Limb Cutaneous Sensation Image: Radial nerve cutaneous peripheral branches. Image: Musculocutaneous nerve cutaneous peripheral branches. Image: Ulnar nerve cutaneous peripheral branches. Image: Median nerve cutaneous peripheral branches. Images from Miller’s Anatomy of the Dog 5th Ed 2020 pp. 720- 725 5