Forelimb Muscles PDF

Forelimb Muscles Nerves Dr Shiann Lallack Dr Juel Dulan Muscles of the Forelimb ➔ Name of muscle ➔ Action ➔ Origination ➔ Insertion ➔ Innervation (nerve supply) 3D muscles https://sketchfab.com/3d-models/dog-forelimb-muscles-1-db19c99a5bda4e99a619717a427fb797 Extrinsic...

Forelimb Muscles Nerves Dr Shiann Lallack Dr Juel Dulan Muscles of the Forelimb ➔ Name of muscle ➔ Action ➔ Origination ➔ Insertion ➔ Innervation (nerve supply) 3D muscles https://sketchfab.com/3d-models/dog-forelimb-muscles-1-db19c99a5bda4e99a619717a427fb797 Extrinsic Muscles of the FL Originate from outside of the thoracic limb e.g. cervical vertebrae etc Insert on the thoracic limb e.g. on the scapula or humerus etc 2 groups: Superficial group Deep group 1) Brachiocephalicus 1) Rhomboideus 2) Omotransversarius 2) Deltoideus 3) Latissimus dorsi 3) Deep pectoral 4) Trapezius 5) Superficial pectoral Superficial Group Brachiocephalicus Omotransversarius Latissimus dorsi Trapezius Superficial Pectoral BOLTS 1) Brachiocephalicus 2 parts Cleidobrachialis and Cleidocephalicus Long, wide muscle Extends from brachium to head and neck Clavicular intersection is the origin point for the 2 parts ○ Remnant of the clavicle located cranial to the shoulder A) Cleidobrachialis Insertion: cr. border of humerus B) Cleiodocephalicus- further divided into 3 parts 1. Pars mastoidea (cleidomastoideus)………….mastoid process of skull (temporal bone) 2. Pars cervicis (cleidocephalicus)……………neck (cervical area) 3. Pars occipitalis (cleidooccipitalis)………..occipital bone of skull (nuchal crest) Horse: 1 only Action: lateral and ventral flexion of head & neck; extend shoulder Dog: 1 & 2 Innervation: Accessory + Axillary n Ox: 1 & 3  Dog has? 2 Cleidomastoideus Cleidocephalicus 1 2) Omotransversarius Strap like muscle Adjacent to brachiocephalicus Origin: wing of atlas C1 Insertion: distal scapular spine Action: advance and adduct limb; flex neck laterally Nerve: Accessory n. 3) Latissimus dorsi Broad, flat, roughly triangular Caudal to the scapula Origin: thoracolumbar fascia Insertion: teres major tuberosity Action: Flexes shoulder; advances limb Nerve: Thoracodorsal n. 4) Trapezius Broad, flat, roughly triangular Caudal to scapula Cranial part and cervical part ○ Trapezius cervicis ○ Trapezius thoracis Origin: C2 to T10 Insertion: Spine of scapula Action: elevates shoulder, draws scapula cranially and caudally Nerve: Accessory n. 5) Superficial Pectoral 2 parts ○ one runs cranially descending part or pectoralis descendens ○ the other runs caudally transverse part or pectoralis transversus Origin: cranial part sternum Insertion: crest of the greater tubercle Action: adducts and advances the limb Nerve: Cr. pectoral n. You need a BOAT to stay afloat! Brachicephalicus Omotransversarius → Accessory n. Trapezius Deep Group Deep Pectoral Rhomboideus Serratus Ventralis DRs 1) Deep pectoral Also called pectoralis profundus ○ Has cranial and caudal parts ○ Cranial part is deep to superficial pectoral ○ Caudal part is larger and also called the ascending part Origin: ventral part of the sternum…. Insertion: Greater and lesser tubercle of H Action: adduct limb, retracts limb, draws trunk toward the limb, Nerve: caudal pectoral n. + lateral thoracic n. 2) Rhomboideus 3 parts ○ Rhomboideus cervicis ○ Rhomboideus thoracis ○ Rhomboideus capitis → in canines and pigs Located deep to trapezius Origin: C2 to T7 (capitis from nuchal crest) Insertion: dorsal border of scapula Action: elevates forelimb and draws scapula against the trunk Nerve: dorsal branches of cervical and thoracic spinal nerves 3) Serratus ventralis Large, fan-shaped muscle 2 parts (cervical and thoracic) Origin: transverse processes of C3-5; Ribs 1-7 or 8 Insertion: serrated faces of medial surface of scapula (facies serrata) Action: Nerve: Long thoracic n. + ventral branches of cervical spinal nerves Subclavius m. Pectoral muscle ABSENT in Carnivores PRESENT in Horse and goat (small muscle in ox) Intrinsic Muscles of the FL Originate and insert on the thoracic limb Can either be discussed based on their action E.g. flexors of the shoulder, flexors of the elbow etc Or we can discuss them based on where they are located I.e. Lateral muscles of the scapula, medial muscles of the scapula etc. Make the link with all of features of the bones that we discussed in detail Scapular muscles act on the shoulder joint Lateral muscles Lateral muscles Supraspinatus Infraspinatus Medial muscles Subscapularis Coracobrachialis Caudal muscles Teres major and minor Deltoideus (caudolateral) 1) Supraspinatus Shoulder EXTENSOR Occupies the supraspinous fossa (cranial) Acts as the “lateral collateral ligament” of the shoulder joint - stabilization Trapezius m. needs to be reflected to visualize Origin: supraspinous fossa Insertion:Greater tubercle Action:extends and stabilizes shoulder Nerve: Suprascapular n. 2) Infraspinatus Shoulder FLEXOR and abductor Same function as supraspinatus in terms of stability Origin: infraspinous fossa Insertion: Greater tubercle Action:flexes, stabilizes and abducts shoulder Nerve: Suprascapular n. 3) Subscapularis Shoulder EXTENSOR and adductor Acts as the “medial collateral ligament” to stabilize the shoulder joint Origin: subscapular fossa Insertion: Lesser tubercle Action:extends, adducts and stabilizes shoulder Nerve: Subscapular n. 4) Coracobrachialis Shoulder FLEXOR Origin: coracoid process Insertion: lesser tubercle Action:flexes and abduct shoulder Nerve: Musculocutaneus n. 5) Deltoideus 2 parts (scapular part and acromial part) ○ Horse and pig will just have scapular part. Why? Origin: spine of scapula and acromion process Insertion: Deltoid tuberosity Action:flexes shoulder Nerve: Axillary n. 5) Teres major and minor FLEXORS of shoulder Teres minor plays a role in stabilization Need to reflect deltoid to see T. minor Origin: Caudal border of scapula Insertion: Teres major and minor tuberosities Action:flexes shoulder Nerve: Axillary n. Coracobrachialis Teres minor  Brachial muscles Act on the elbow joint Flexor muscles Lateral muscles Biceps brachii Brachialis Extensor muscles Triceps brachii Tensor fascia antebrachii Anconeus 1) Biceps brachii Major role: Elbow FLEXOR BBT passes through the intertubercular groove -> extends shoulder Origin: Supraglenoid tubercle Insertion: Radial tuberosity Action: flexes elbow Nerve: Musculocutaneous n. 2) Brachialis FLEXOR of elbow Muscle belly runs along the musculospiral groove Origin: Caudolateral surface of prox. humerus Insertion: Radial tuberosity Action: flexes elbow Nerve: Musculocutaneous n. HORSE/Pig 3) Triceps brachii Essential for weight bearing in the forelimb 4 heads ○ Long - originates on the caudal border of the scapula ○ Lateral ○ Medial ○ Accessory - not present in horse Origin: Humerus (except the long head) Insertion: Olecranon Action: extends elbow Nerve: Radial n. 4) Tensor fasciae antebrachiii EXTENSOR of elbow Thin strap that lies of the medial aspect of the long head of T. brachii Origin: Latissimus dorsi Insertion: Olecranon Action: extends elbow Nerve: Radial n. 5) Anconeus EXTENSOR and stabilizer of elbow joint Crosses the lateral aspect of elbow under the triceps Origin: Distal humerus Insertion: Olecranon Action: extends elbow Nerve: Radial n.  Antebrachial muscles Act on the carpal joint and digital joints  Extensor group Flexor group (Craniolateral) (Caudomedial) Extensor carpi radialis Superficial digital flexor Common digital extensor Deep digital flexor Lateral digital extensor Flexor carpi radialis Ulnaris lateralis Flexor carpi ulnaris Others…… Lateral epicondyle Medial epicondyle Others: Pronators Supinator Extensor group (Craniolateral) Extensor carpi radialis ○ Insertion: metacarpal tuberosity ○ Extends carpus; flexes elbow Common digital extensor ○ Insertion: extensor process of P3 ○ Extends carpus + digits Lateral digital extensor ○ Insertion: Phalanges of lateral digits ○ Extends carpus + digits Ulnaris lateralis ○ Insertion: proximal Mc + Accessory Cb ○ FLEXES carpus Supplied by RADIAL N. Some more extensors: only found in carnivores 1) Oblique carpal extensor Other names: ○ Long digital I abductor ○ Abductor digiti I pollicis longus Found on the cranial surface of the forearm Adducts digit 1 and extends the carpus 2) Extensor pollicis longus et indicis proprius Extends digits 1 and 2 Also supplied by the RADIAL N. Flexor group (Caudomedial) Superficial digital flexor ○ Insertion: palmar surface of P3 ○ Flexes digits + carpus Deep digital flexor ○ 3 heads (radial, humeral + ulnar) ○ Insertion: P3 ○ Flexes carpus + digits Flexor carpi radialis ○ Insertion: Prox. metacarpus ○ Flexes carpus Flexor carpi ulnaris ○ 2 heads (ulnar + humeral) ○ Insertion: Accessory Cb ○ Flexes carpus Supplied by ULNAR N. + Median nerve Hence you rarely have complete paralysis of all extensors Pronators: pronate paw (turn paw downward so that paw pads face the ground) 1) Pronator teres Obliquely extends from med. epicondyle to med. surface of radius 2) Pronator quadratus A short muscle located deep to the DDF Runs along the length of the interosseous space Supplied by Median N. Supinators: supinates paw (turn paw upward) 1) Supinator From lat. epicondyle to radius 2) Brachioradialis A short muscle located deep to the DDF Also runs along the length of the interosseous space Supinate the paw Supplied by RADIAL N. Nerves of the Forelimb Brachial Plexus Network of nerves formed from the ventral branch of last three cervical and first two thoracic spinal nerves (C6,7,8 &T1,2) Brachial plexus supplies all muscles of forelimb except -trapezius -omotransversarius -brachiocephalicus -rhomboideus -skin over upper shoulder region 11 nerves originate from the brachial plexus to innervate forelimbs muscles include:- Suprascapular n. Pectoral nerves Subscapular n. Long thoracic n. Axillary n. Lateral thoracic n. Musculocutaneous n. Ulnar n. Radial n. Thoracodorsal n. Median n SUPRASCAPULAR N. (C6, C7) Path:- Travels between the supraspinatus and subscapularis muscles, across the cranial aspect of the scapula Muscles innervated- - supraspinatus m. - infraspinatus m. Muscles actions:- Stabilization and extension of the shoulder joint. CLINICAL:- Vulnerable to injury In cases of “Over Abduction of Violent retraction” , the Suprascapular Nerve is stretched against the scapula,, CAUSING SHOULDER SLIP/ SWEENEY. - LACK OF ACROMION PROCESS increases susceptibility. SUBSCAPULAR N. (C6, C7) Path:- passes into subscapularis m., directly from brachial plexus. Muscles innervated:- -Subscapularis m. Action of muscle- Adduct the limb and rotate humerus medially. MUSCULOCUTANEOUS N. (C6, C7, C8) Path:- runs along the medial aspect of the brachium, passes the biceps brachii and brachialis m.; gives off sensory innervation to medial antebrachium. Muscles innervated:- -biceps brachii m. - brachialis m. -coracobrachialis m. Muscle actions- Shoulder extensors and Elbow flexors CLINICAL:- Dysfunction of musculocutaneous n. in DOG causes:- little change in the gait (flexion of elbow requires activity of at least one of biceps brachii, brachialis & coracobrachialis muscles. Unable to respond to invitation to offer a paw AXILLARY N. (C7,C8) Path:- passes caudally around shoulder joint between subscapularis m. and teres major m. Muscles innervated:- - Deltoideus m. - Teres major m. - Teres minor m. - Part of the subscapularis m. Muscle actions:- Flexors of the shoulder joint; Rotates brachium.  RADIAL N. (C7, C8, T1, T2) Path:- wraps around the humerus laterally, then travels distally on the lateral side of the limb. Muscles innervated:- - Extensors of carpus and digits - extensor carpi radialis - common digital extensor - lateral digital extensor. - Triceps brachii m. (elbow extension) RADIAL N. PARALYSIS High Radial Nerve Paralysis (more Low Radial Nerve Paralysis common) Site of damage: PROXIMAL TO MIDDLE OF ARM- DISTAL to Triceps brachii Innervation Triceps brachii innervation site site MEDIAN N. ( C8. T1, T2) Path:- Travels along the medial side of the forelimb, enters forearm over the medial collateral ligament of the elbow joint. Divides in the distal part of the forearm in to two more divisions (medial and lateral palmar nerves). It is often closely associated with Ulnar N. It continues distally to Palmar surface of paw. Muscles innervated: most FLEXORS OF CARPUS AND DIGITS. - Flexor carpi radialis m. -superficial digital flexor m. -sensory innervation to palmar surface of paw. -pronator teres ; pronator quadratus -deep digital flexor m. - humeral, radial ulnar heads CLINICAL:-\ Dysfunction of median nerve in the dog -----carpus became more extended “Raised Claws” ULNAR N. ( C8, T1, T2) Path:- runs caudally w/ Median n. But diverges distally to lateral aspect of antebrachium, Muscles innervated:- - Flexor carpi ulnaris m. - Interosseous m. - Sensory innervation to caudal forelimb and lateral digits. –Dorsal branch supply skin on the lateral aspect of the forefoot –Palmar branch supplies interosseous and other small muscles of foot and supplies sensory branches to skin and deep structures THORACODORSAL N.( C8) Path:- travels caudally on the medial aspect of the limb. Muscles innervated:- Latissimus dorsi m. Muscle actions:- Retracts the limb. LATERAL THORACIC N. (C8, T1) - Path:- Travels caudally to the axilla, innervating cutaneous trunci m. and to skin over the ventral part of the thorax and abdomen - Action of m. - Panniculus reflex - skin twitching LONG THORACIC N.- –Innervates the serratus ventralis PECTORAL N. (C6-T1) Path:- –Cranial and Caudal branches that supply the pectoral m. Muscles innervated:- superficial and deep pectoral m. including subclavius Muscle actions:-adduct the limb Why does the brachial plexus have 8 spinal nerves? All mammals have 7 cervical vertebrae So wouldn't they have 7 spinal nerves for each respective vertebrae? Recall spinal cord anatomy We have ‘roots’ emerging from the spinal cord Dorsal roots and ventral roots Both join to form a spinal nerve The spinal nerve exits through the intervertebral formamina of the vertebrae  Where the spinal nerves begin, they exit cranial to the first cervical vertebrae They then exit caudal to their respective vertebrae Therefore there are 8 cervical spinal nerves while the rest of spinal nerves correspond to their respective number of vertebrae Eg dogs have 13 thoracic vertebrae therefore they will have 13 thoracic spinal nerves