Brachial Plexus (Scheme + Quiz) | Anatomy

Summary

This video provides an in-depth explanation of the brachial plexus, a vital network of nerves that innervates the upper limb. It covers the topography of the brachial plexus, including the spinal nerve roots, trunks, divisions, cords, and main nerves such as the musculocutaneous, radial, median, axillary, and ulnar nerves. The video breaks down the anatomy and function of each nerve, detailing their courses, branches, and muscle innervations. It also highlights smaller nerves and their functions, such as the dorsal scapular and long thoracic nerves. A final quiz reinforces key concepts for better understanding and retention.

Takeaways

• 😀 The brachial plexus is formed by the anterior branches of spinal nerves C5, C6, C7, C8, and T1, with C4 sometimes contributing.
• 😀 The brachial plexus is divided into 5 main sections: Roots, Trunks, Divisions, Cords, and Nerves. A helpful mnemonic to remember this is 'Really Tired, Drink Coffee Now'.
• 😀 The brachial plexus starts with the formation of three trunks: superior (C5-C6), middle (C7), and inferior (C8-T1).
• 😀 From each trunk, anterior and posterior divisions are formed. The posterior divisions combine to form the posterior cord, while anterior divisions form the lateral and medial cords.
• 😀 The main nerves of the brachial plexus include the Musculocutaneous, Axillary, Radial, Median, and Ulnar nerves, each with specific functions.
• 😀 Small branches from the roots include the Dorsal Scapular Nerve (supplies rhomboids and levator scapulae) and Long Thoracic Nerve (supplies serratus anterior).
• 😀 The suprascapular nerve (from the superior trunk) supplies the supraspinatus and infraspinatus muscles, which are involved in shoulder abduction and rotation.
• 😀 The posterior cord branches into the Upper Subscapular Nerve (supplies subscapularis), Lower Subscapular Nerve (supplies subscapularis and teres major), and Thoracodorsal Nerve (supplies latissimus dorsi).
• 😀 The medial cord gives off the Medial Pectoral Nerve (supplies pectoralis major and minor) and other branches like the medial cutaneous nerves of the arm and forearm.
• 😀 The Musculocutaneous Nerve innervates the muscles of the anterior arm (biceps brachii, brachialis, coracobrachialis) and provides cutaneous sensation to the lateral forearm.
• 😀 The Ulnar Nerve innervates muscles of the hypothenar eminence, interossei, and some lumbricals, and provides sensory innervation to the ulnar side of the hand.

Q & A

What is the primary function of the Brachial Plexus?

The Brachial Plexus is responsible for providing sensory and motor innervation to the upper extremities, including the arm, forearm, and hand.

Which spinal nerve roots contribute to the formation of the Brachial Plexus?

The Brachial Plexus is primarily formed by the anterior branches of the spinal nerves C5, C6, C7, C8, and T1, with some variations including contributions from C4.

What mnemonic is commonly used to remember the Brachial Plexus structure?

A popular mnemonic for remembering the order of Brachial Plexus structures is 'Really Tired, Drink Coffee Now,' which stands for Roots, Trunks, Divisions, Cords, and Nerves.

What happens to the C5 and C6 roots in the Brachial Plexus?

The C5 and C6 roots combine to form the Superior Trunk of the Brachial Plexus.

How are the divisions of the Brachial Plexus formed?

Each trunk (Superior, Middle, and Inferior) divides into an anterior and a posterior division. These divisions later combine to form cords.

What is the function of the Posterior Cord of the Brachial Plexus?

The Posterior Cord is formed by the posterior divisions of the upper, middle, and lower trunks and gives rise to the Radial and Axillary nerves.

Which nerves arise from the Lateral Cord of the Brachial Plexus?

The Lateral Cord forms the Musculocutaneous nerve and contributes to the formation of the Median nerve.

What role does the Ulnar Nerve play in the upper limb?

The Ulnar nerve provides motor innervation to the hypothenar muscles and other hand muscles, and sensory innervation to the medial part of the hand, including the 5th digit and the ulnar side of the 4th digit.

How does the Median Nerve contribute to hand function?

The Median nerve innervates most of the anterior forearm muscles and the thenar muscles of the hand, enabling functions like flexion, opposition, and pronation.

What is the significance of the Dorsal Scapular Nerve in the Brachial Plexus?

The Dorsal Scapular Nerve, which arises from the C5 root, supplies the Rhomboid Major and Minor muscles, as well as the Levator Scapulae, and is responsible for scapular retraction and elevation.