Anatomy Lecture 2 (Cervical & Brachial Plexuses) 2024 PDF

Lecture N2 Spinal nerves - Cervical plexus; Brachial plexus. Nerve plexuses - combined somatic or visceral nerve fibers from different sources or levels that form new nerves with specific targets or destinations.  Cervical Plexus C1 – C4 anterior rami w...

Lecture N2 Spinal nerves - Cervical plexus; Brachial plexus. Nerve plexuses - combined somatic or visceral nerve fibers from different sources or levels that form new nerves with specific targets or destinations.  Cervical Plexus C1 – C4 anterior rami with contributions from C5 Sensory (cutaneous) nerves  Mixed nerve  Motor nerves  strap muscles diaphragm (phrenic nerve) skin on the anterior and lateral parts of the neck skin of the upper anterior thoracic wall skin on the inferior parts of the head. Ansa Cervicalis (Lat. “handle of the neck”) Motor Branches  Superior root of ansa cervicalis (C1)  Geniohyoid (C1)  Thyrohyoid (C1)  Inferior root of ansa cervicalis (C2-C3)  Superior belly of omohyoid  Inferior belly of omohyoid  Sternohyoid  Sternothyroid Ansa Cervicalis (Lat. “handle of the neck”)  Two branches from C1 1. Geniohyoid m. – elevates the 2. Thyrohyoid m. – depress the hyoid bone hyoid bone, elevates larynx Branches of Ansa Cervicalis Omohyoid muscle – superior belly and inferior belli Separated by intermediate tendon Attachment: proximally – scapula, distally – hyoid bone. Omohyoid m. – depresses and fixes the hyoid bone and larynx Sternothyroid and Sternohyoid mm. Sternothyroid m. – depresses the hyoid bone and larynx (chewing, swallowing and speaking) Sternohyoid m. – depresses the hyoid bone during speech and swallowing.  Cervical Plexus Sensory Branches Sensory branches – skin of the lateral neck and lateral scalp, emerge from behind the midpoint of the posterior border of the sternocleidomastoid muscle.  Loop between C2 – C3:  Lesser occipital nerve (C2)  Great auricular nerve (C2 - C3)  Transverse cervical nerve (C2 - C3)  Loop between C3 - C4: Supraclavicular nerve (C3-C4) C1 – C2 Interconnecting Loop Rectus capitis lateralis – flexes the head on the neck (atlantooccipital joint) Rectus capitis anterior – flexes the head on the neck at the atlantooccipital joint and stabilizes the atlantooccipital joint  C1 – C2 Interconnecting Loop Longus capitis – weak flexor of the head and cervical spine C2 Ramus Longus colli (upper, middle, lower mm.) – flexes forward and lateral, rotates the neck  C3 Ramus Scalene (middle, posterior, anterior mm.) – elevates the first rib, flexes and laterally bends the neck to the same side. C3 and C4 Rami Nerves to trapezius muscle – elevates, depresses, and retracts the scapula  Mixed Nerve Phrenic nerve (C3 – C5) – descends to the thoracic region (mediastinum) Motor – Diaphragm Sensory – central part of diaphragm, pericardium, mediastinal pleura, diaphragmatic pleura, diaphragmatic peritoneum. Brachial Plexus  Brachial Plexus Root Divisi Branch Trunk Cord on es Musculocutaneous Axillary nerve Radial nerve Median nerve Ulnar nerve Brachial Plexus  Brachial Roots Roots Trunks Divisions Cords C5 – C6 – Upper/superior trunk C7 – Middle trunk C8 – T1 – Lower/inferior trunk  Divisions of the trunks Roots Trunks Divisions Cords Within the posterior triangle of the neck each trunk gives two branches:  Anterior (3 nerve fibers)  Posterior (3 nerve fibers) The divisions pass into the axilla region and recombine in the next part of the brachial plexus.  Brachial Cords Roots Trunks Divisions Cords  The lateral cord is formed by: The anterior division of the superior trunk The anterior division of the middle trunk  The posterior cord is formed by: The posterior division of the superior trunk The posterior division of the middle trunk The posterior division of the inferior trunk  The medial cord is formed by: The anterior division of the inferior trunk. The cords give rise to the major branches of the brachial plexus. Musculocutaneous Nerve C5 – C7 Motor function Anterior compartment of the arm – flexor muscles (BBC): Biceps brachii Brachialis Coracobrachialis Musculocutaneous Nerve C5 – C7 Sensory function (via lateral cutaneous nerve of forearm) Skin on the lateral surface of the forearm Median Nerve (C6 - T1) It does not innervate any structures in the arm!!! Motor function Anterior compartment: Most of the superficial and deep flexors in the forearm (except flexor carpi ulnaris and ulnar head of the flexor digitorum profundus) Median nerve (C5 – C7) Motor innervation (LOAF): Lateral two lumbricals Opponens pollicis Abductor pollicis brevis Flexor pollicis brevis Thenar eminence Median Nerve (C6 – T1) Sensory function Anterior compartment: Palmar cutaneous branch - the lateral aspect of the palm Digital cutaneous branch Ulnar Nerve (C8-T1) Motor function Anterior compartment: Flexor carpi ulnaris Medial half of flexor digitorum profundus Flexor digiti minimi Abductor digiti minimi Opponens digiti minimi Median two lumbricals Muscles innervated by ulnar nerve Ulnar nerve (C8 – T1)  Sensory innervation: Anterior aspect off the ulnar 1½ fingers (little finger and half of the ring finger) and medial palmar skin. Dorsal aspect of the ulnar 1½ fingers and medial aspect of dorsum of hand Radial Nerve (C5-T1) Motor function Posterior compartment – extensor muscles: Triceps brachii (extend the arm at the elbow) Brachioradialis Extensor carpi radialis longus Deep branch - remaining muscles of the posterior forearm (extend at the wrist and finger joints, and supinate the forearm) Radial Nerve (C5-T1) Sensory branches Inferior lateral cutaneous nerve of arm Posterior cutaneous nerve of arm Posterior cutaneous nerve of forearm Superficial branch of the radial nerve  Axillary nerve (C5 – C6)  Motor innervation:  Deltoid m. Teres minor m. Lateral head of the triceps brachii m. Axillary nerve (C5 – C6)  Sensory innervation: Glenohumeral joint Skin of the deltoid region/upper arm.  Root  Long thoracic nerve (C5 – C7, anterior rami) Descends posteriorly to the brachial plexus, axillary artery and vein and anteriorly to the posterior scalenus muscle. Serratus anterior m. (“boxer’s muscle”, throwing a punch) – rotates the scapula, allows the arm to be raised over 90 degree, holds the scapula against the ribcage.  Damage of the nerve - weakness of the serratus anterior, producing a characteristic “winged scapula” appearance.  Root Dorsal scapular nerve (C5, anterior ramus) Pierces the middle scalene m. and descends between the levator scapulae and serratus posterior superior & scalenus posterior mm. Periscapular stabilizing muscles: Levator scapule m. Rhomboid major m. Rhomboid minor m. Elevate and retract the scapula  Trunk Suprascapular nerve (C5 – C6) Motor function - rotate cuff muscles: Supraspinatus m. Infraspinatus m. Sensory function Glenohumeral joint Acromioclavicular joint  Trunk Subclavian nerve (C5 – C6) Subclavius m. depresses the lateral clavicle stabilizes the clavicle while the shoulder moves the arm raises the first rib while lowering the clavicle during breathing protects the underlying brachial plexus and subclavian vessels from a broken clavicle Medial Cord Branches (C8-T1)  Medial brachial cutaneous nerve  Medial antebrachial cutaneous nerve  Medial pectoral nerve  Ulnar nerve  Median root of median nerve  Medial Cord Branches Pectoralis minor Pectoralis major Lateral Cord Branches (C5-C7)  Musculocutaneous n.  Lateral pectoral n. – pectoralis minor m.  Lateral root of median n. (forms median n. with median root) Posterior Cord Branches (C5-C6) Subscapular n. (upper and Lower) – subscapular m. Thoracodorsal n. – latissimus dorsi m. Radial nerve Axillary nerve  Brachial Plexus Nerves Root Anterior Cords Long thoracic nerve Dorsal scapular nerve Lateral Cord Trunk Lateral pectoral (upper) Nerve to subclavius Musculocutaneous Suprascapular nerve Lateral root of median nerve Posterior Medial Cord Cord Upper subscapular nerve Medial pectoral Lower subscapular nerve Medial cutaneous nerve of arm Thoracodorsalis Medial cutaneous nerve of forearm Axillary nerve Ulnar nerve Radial nerve Median root of median nerve  Muscles innervated by the brachial plexus nerves Dorsal scapular nerve – levator scapule, rhomboids (major, minor) Long thoracic nerve - the serratus anterior Suprascapular nerve - the supraspinatus and infraspinatus Subclavian nerve – subclavian muscle Lateral pectoral nerve - the pectoralis major Medial pectoral nerve - both pectoralis major and minor Upper subscapular nerve - the subscapularis Lower subscapular nerve - the subscapularis and teres major Thoracodorsal nerve - the latissimus dorsi Medial brachial cutaneous nerve - the skin of the arm medially Medial antebrachial cutaneous nerve - the skin of the forearm medially Cubital Tunnel Syndrome aw  hand" Brachial Plexus Palsy/Erb’s Palsy Damage to the upper part of the brachial plexus nerves (stretching or tearing) – muscular weakness or paralysis. The most common type is neurapraxia (the nerve is stretched but not torn). Klumpke’s Palsy Damage to the lower part of the brachial plexus nerves (stretching or tearing) – Causes muscular weakness or paralysis. Carpal Tunnel Syndrome Occurs when median nerve is pressed or squeezed at the wrist. Causes numbness, weakness, pain in hand and wrist.  Median Nerve Injury  Distal humerus is often caused by a supracondylar fracture and result in loss of sensation in the palm and palmar surface of the lateral three and a half digits, loss of flexion of 1st to 3rd digits, weakened flexion of 4th and 5th digits, loss of thenar opposition, loss of pronation  “Hand of benediction” (preacher’s hand ) is produced by flexing the hand in a fist (2nd and 3rd digits remain partly extended); injury of flexor digitorum superfacialis, flexor digitorum profundus  Cause: compression or injury of the median nerve at the forearm or elbow  “Ape hand” produced by flattening of the thenar eminence Ulnar Nerve VS Median Nerve  Axillary Nerve Injury  Axillary nerve is most vulnerable as it courses around the neck of the humerus and can be injured by:  Fractures at the surgical neck  Dislocation of the glenohumeral joint These result in the following:  Weakened lateral rotation at the shoulder  Inability to abduct the shoulder even to the horizontal position  Loss of sensation over the deltoid region  A flattened shoulder contour  Links https://www.youtube.com/watch?v=bNicIEt-_SM&t=465s https://www.youtube.com/watch?v=IxInfkIfn0E https://www.youtube.com/watch?v=RLJ8aUw468M&t=21 4s Thank you