NMSK - forelimb anatomy

what is the name of the joint found in the shoulder

glenohumeral joint

what 3 joints are found in the elbow

humeroulnar

humeroraidal

proximal radioulnar

What is the role of extrinsic muscles?

• attachment of the limb to the axial skeleton

Name the 6 extrinsic muscles of the forelimb

1. trapezius muscle (cervical and thoracic part)

2. rhomboideus muscle (cervical and thoracic part)

3. brachiocephalicus muscle (cleidocervicalis, cleidobrachialis and further division into cleidooccipitalis and cleidomastoideus)

4. omostransversarius muscle

5. latissimus dorsi

6. superficial pectoral muscle (transverse and ascending parts)

Outline the trapezius muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: funicular part of nuchal ligament on cervical and thoracic region

Insertion: spine of scapula by a flat aponeurosis

Action: contraction elevates the scapula

Extrinsic

• has a cervical and thoracic part

Outline the rhomboideus muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin:

• rhomboideus cervicis: funicular part of nuchal ligament b/w C2 and T2

• rhomboideus thoracis: thoracic spines

Insertion: Dorsal and medial borders of scapular cartilage

Action: draws scapula dorsally

Extrinsic

• In the dog, also has a part called rhomoideus capitis

• in some breeds of cattle, a hump is present (an enlargement of the rhomboideus muscle) - not european breeds

Outline the brachiocephalicus muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

origin = clavicular intersection cranial to shoulder joint

insertion:

• cleidobrachialis: brachium or crest of humerus

• cleidoccipitalis: nuchal crest and funicular nuchae

• cleidomastoideus: Mastoid process of petrous division of temporal bone

Action: dependent on if the limb is weight bearing or free to swing.

• during motionL extends shoulder joint and advances whole limb forward

• contraction on one side of the neck (ipsilateral muscle), pulls head and neck laterally

• head is pulled ventrally when both contact (on either side of neck)

Extrinsic

• cleidoccipitalis is absent in horse

• cleidomastoideus forms ventral part of cleidocephalicus and forms dorsal boundary of external jugular groove.

Outline the Omotransversarius muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Acromion of scapula

Insertion: Part of axis and wing of atlas (C1)

Action: bends neck laterally

Extrinsic

• located deep to this muscle are the superficial cervical lymph nodes

Outline the Latissimus Dorsi muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Thoracolumbar fascia on dorsal midline of thorax and lumbar regions

Insertion: Teres major tuberosity on medial-proximal side of humerus

Action: depends on limb position

• draws limb caudally when limb is free

• Draws trunk cranially when limb is fixed

Outline the superficial pectoral muscle (descending and transverse parts); origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin:

• descending = manubrium

• transverse = 2-6 sternebrae

Insertion:

• descending = crest of humerus

• transverse = proximal one-third of the medial forearm

Outline the Deep (ascending) pectoral muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Median raphe along entire ventral surface of sternum

Insertion: Lesser and greater tubercle on proximal humerus

Action: Adducts and draws limb caudally when limb is free to swing

when limb is advances and fixed = advances trunk

extrinsic

• thicker than superficial pectoral muscle

Outline the Serratus Ventralis muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Last 4-5 cervical vertebrae, first 7-8 ribs

Insertion: serrated surface of scapula

Action:

• Cervical part = draws scapula cranially when limb swings caudally

• Thoracic part = moves scapula caudally when limb is advanced cranially

• act as a ‘sling system’ to support trunk

Extrinsic

• has a thoracic and cervical part

• Different attachment than normal - bone-muscle-bone = synsarcosis, part of thoracic sling

Outline the Subclavis muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: First rib cartilage

Insertion: Clavicular intersection of brachiocephalicus muscle

Action: none that deserves attention

what is the role of intrinsic muscles

• movement of the limb

what are the 2 groups of muscles on the antebrachium

• Caudolateral

• Caudomedial

Name the 12 intrinsic muscles

1. supraspinatus

2. infraspinatus

3. deltoideus

4. teres minor

5. teres major

6. subscapularis

7. triceps brachii muscle

8. anconeus

9. tensor fasciae antebrachii

10. biceps brachii

11. brachialis

Name the acronym used and the first 4 extensor muscles, what side of the distal limb are these found?

ECLU

• Extensor carpi radialis

• Common digital extensor

• Lateral digital extensor

• Ulnaris lateralis

• Extensor carpi obliquus

Craniolaterally

Name the 5 muscles found caudomedially on the distal limb

• Flexor carpi ulnaris

• Flexor carpi radialis

• SDF muscle - flexor manica

• DDF muscle

• Interosseus muscle (suspancial ligament) with axial and abaxial extensor branches

what are the 2 retinacula muscles?

• Extensor retinaculum (deep fascia-dorsal carpus)

• Flexor retinaculum (deep fascia-palmar carpus)

what are the ligaments of the digits

• annular ligaments

• interdigital

Outline the supraspinatus muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

origin: supraspinous fossa

Insertion: split insertion on greater and lesser tubercles

Action: stabilised and extends shoulder joint

Outline the Infraspinous muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: supraspinous fossa

Insertion:

• deep tendon = proximal caudal border of greater tubercle

• superficial tendon = distal to greater tubercle

Action = stabilises shoulder joint

Intrinsic

• - infraspinatus subtendinous bursa is deep to superficial tendon in ruminants and most other domestic animals (dog and horse), may be absent in small ruminants.

Outline the teres minor muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: distal third of caudal border of scapula

Insertion: teres minor tuberosity proximal to lateral deltoid tuberosity

Action: flexes shoulder joint

Intrinsic

Outline the Teres major muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

origin: proximal caudal border of scapula

insertion: teres major tuberosity on proximal medial surface of humerus - with insertion tendon of latissimus dorsi

Action: flexes shoulder joint

Intrinsic

what does the acronym DTT stand for?

D= deltoideus

T = teres major

T = teres minor

all flex the shoulder joint

Outline the subscapularis muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: subscapular fossa

Insertion: lesser tubercle

Action: stabilises shoulder joint and adduction of brachium

Outline the triceps brachii muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: caudal border of scapula (long head), proximal to lateral humerus and tricipital line (medial, accessory and lateral heads)

Insertion: Olecranon tuber

Action:

• extend elbow

• Long head flexes shoulder joint

Intrinsic

• Horse only has 3 heads (no accessory)

• other species have long, lateral, accessory and medial heads

• accessory head is only small in ruminants and may be absent

Outline the Anonceus muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Caudodorsal part of humerus (olecranon tuber)

Insertion: lateral surface of olecranon

Action:

• extends elbow joint.

• Tenses elbow joint capsule during extension

Outline the tensor fasciae antebrachii muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: Caudal border of scapula

Insertion: olecranon tuber and deep antebrachial fascia

Action: extends elbow

Outline the Coracobrachialis muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

origin: coracoid process of scapula

Insertion:

• Horse = teres major tuberosity

• Ruminants = distal medial surface of humerus, distal to teres major tuberosity

Action: flexes, adducts and stabilises shoulder joint

Intrinsic

Outline the Biceps Brachii muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: supraglenoid tubercle

Insertion: radial tuberosity and medial elbow region

Action: flexes elbow and extends shoulder joint

Intrinsic

Features:

1. transverse humeral retinaculum (a flat tissue structure). Wraps around tendon of origin - prevents eversion of tendon from intertubercular groove

2. intertubercular bursa - under tendon of origin.

• In bovine and equine = independent synovial sac

• Dogs - extension of shoulder joint capsule

Outline the brachialis muscle; origin, insertion, action, intrinsic/extrinsic and any additional notes

Origin: proximal part of caudal surface of humerus and brachialis groove

Insertion: Medial elbow and proximal part of medial surface of radius (cattle) and medial coronoid process of ulna (goats)

Action: flexes elbow joint

what are 4 common characteristics of the craniolateral muscle group in the distal limb?

1. common origin from lateral epicondyle of humerus, exception of extensor carpi radialis and obliquus

2. all are innervated by the radial nerve

3. collectively extend the carpus with some extending digital joints too

4. located on the craniolateral aspect of antebrachium

Outline the extensor carpi radialis muscle; origin, insertion, action and any additional notes

Origin: lateral supracondylar crest and radial fossa

Insertion: metacarpal tuberosity at base of Mc III and IV

Action: extends carpus

Outline the Common digital extensor muscle; origin, insertion, action and any additional notes

Origin: lateral epicondyle of humerus

Insertion:

• medial tendon - P2 and extends to P3 (ox) of medial digit.

• splits into two thin tendons that insert on extensor processes of P3 of digits III and IV

Action: Extends carpus and digital joints

Outline the Lateral digital extensor muscle; origin, insertion, action and any additional notes

origin: Lateral epicondyle of humerus and lateral collateral ligament of elbow

Insertion: on P2 and P3 (ox) of lateral digit IV

Action: extends carpus on phalangeal joint of digit IV

Outline the Ulnaris lateralis muscle; origin, insertion, action and any additional notes

Origin: lateral epicondyle of the humerus

Insertion: accessory carpal bone and Mc IV/V

Action: flexes or extends carpus depending on position and action of other muscles

Outline the Extensor carpi obliquus muscle; origin, insertion, action and any additional notes

Origin: lateral distal half of the body of the radius, deep to the common and lateral digital extensor muscles

Insertion: medial-proximal surface of large metacarpal bone

Action: extends carpus

Outline the flexor carpi ulnaris muscle; origin, insertion, action and any additional notes

Origin: Medial epicondyle of humerus and olecranon

Insertion: Accessory carpal bone

Action: Flexes carpus and extends elbow

Outline the flexor carpi radialis muscle; origin, insertion, action and any additional notes

Origin: medial epicondyle of humerus

Insertion: proximomedial surface of large metacarpal bone

Action: flexes carpus

Outline the superficial digital flexor (flexor manica) muscle; origin, insertion, action and any additional notes

Origin: medial epicondyle of humerus

Insertion: palmar surface of middle phalanx of digits III and IV

Action: extends elbow and flexes carpal, fetlock and pastern joints

Additional information:

• split into the SDF and DDF

• join in the mid-metacarpal region to form a single tendon

• SDF acts as a sleeve for the passage of the DDF tendon to the palmar surface of P3

Outline the DDF muscle; origin, insertion, action and any additional notes

Origin:

• ulnar head = olecranon

• radial head = proximal medial radius

• humeral head = medial epicondyle of humerus

Insertion: flexor tubercle of distal phalanx of digits III and IV

Action: extends elbow and flexes carpal, fetlock, pastern and coffin joints

Outline the Interosseus muscle; origin, insertion, action and any additional notes

Also known as suspensory ligament

Origin: Distal row of carpal bones and palmar carpal ligament

Insertion: proximal sesamoid bones

Action: prevents overextension fo fetlock joints by pressure produced from the animal’s weight. Opposes flexor tension.

Additional notes:

• horse has a single suspensory ligament

• more fleshy in ruminants

which nerves are protractors for extrinsic muscles

accessory spinal and/or segmental cervical nerves

which nerves are involved in the thoracic sling for extrinsic muscles

• brachial plexus

• segmental spinal nerves

what nerve is a retractor for extrinsic muscles

brachial plexus

name the 9 nerves that serve the extrinsic nerves

1. accessory spinal

2. spinal segmental C1-C7

3. spinal segmental C5-C8

4. pectoral

5. spinal segmental C6-T7

6. spinal segmental C8-C10

7. long thoracic

8. thoracodorsal

9. lateral thoracic

name the roots of the 9 extrinsic serving nerves

1. accessory spinal - c1-C7 (ascends within spinal canal to exit from skull)

2. spinal segmental - C1-C7

3. spinal segmental - C5-C8

4. pectoral - C6, 7, 8, T1

5. spinal segmental - C6-T7

6. spinal segmental - C8-C10

7. long thoracic - C7, 8

8. thoracodorsal - C8

9. lateral thoracic - C8

name the function of each of the 9 nerves that serve the extrinsic muscles

1. accessory spinal - protraction

2. spinal segmental - C1-C7 - assists accessory spinal

3. spinal segmental - C5-C8 - thoracic sling

4. pectoral - thoracic sling

5. spinal segmental C6-T7 - thoracic sling

6. spinal segmental C8-C10 - thoracic sling

7. long thoracic - thoracic sling

8. thoracodorsal - retraction

9. lateral thoracic - skin twitch

name which muscles are supplied by each of the nerves that serve the extrinsic muscles

1. accessory spinal - long strap neck muscles, trapezius cervicis

2. spinal segmental C1-C7 - long strap neck muscles

3. spinal segmental C5-C8 - serratus ventralis cervicis

4. pectoral - pectoralis grp

5. spinal segmental C6-T7 - rhomboidei

6. spinal segmental C8-C10 - trapezius thoracis

7. long thoracic - serratus ventralis thoracis

8. thoracodorsal - latissimus dorsi

9. lateral thoracic - cutaneous trunci

How is the skin innervated

Segmentally:

• C1 = purely motor

• cervical region = C2-C5

• Dorsal shoulder region = C6-T2 (not C7,8 or T1)

• Dorsal thorax and abdomen = T3-L4

• Lateral thorax and abdomen = lateral cutaneous branches T3-L2

• ventral thorax and abdomen starting at base of neck = T2 - L1

what does the brachial plexus serve?

• intrinsic muscles

what nerves form the plexus?

ventral rami of spinal nerves

what is the location of the plexus

• in axilla i.e. medial to shoulder joint

name the 7 nerves that leave the plexus

1. suprascapular

2. subscapular

3. axillary

4. musculocutaneous

5. radial

6. median

7. ulnar

Name the roots of the 7 nerves that serve the intrinsic muscles

1. suprascapular - C6 (7)

2. subscapular - C6, 7

3. axillary C7, 8

4. musculocutaneous, C (6), 7, (8)

5. radial - C7,8, T1

6. median C8, T1, 2

7. ulnar - C8, T1, 2

name the function of the 7 nerves that serve the intrinsic muscles

1. suprascapular - shoulder stability

2. subscapular - shoulder stability

3. axillary - shoulder flexion

4. musculocutaneous - elbow flexion

5. radial - extension of all shoulder joints exc. shoulder

6. median - flexion of carpus and digits

7. ulnar - flexion of carpus and digits.

name the muscles supplied by the 7 nerves that serve the intrinsic muscles

1. suprascapular - supraspinatus, infraspinatus

2. subscapular - subscapularis, teres major

3. axillary - teres major and minor, deltoideus, cleidobrachialis

4. musculocutaneous - biceps brachii, brachialis, coracobrachialis

5. radial - extensors of elbow, carpus and digits

6. median - flexors of carpus and digits

7. ulnar - flexors of carpus and digits

what is the cutaneous supply provided by the 7 nerves that serve intrinsic muscles?

1. suprascapular

2. subscapular

3. axillary - cranial lateral brachium, lateral antebrachium

4. musculocutaneous - medial antebrachium

5. radial - lateral antebrachium, dorsal carpus

6. median - palmar carpus

7. ulnar - caudal lateral antebrachium digit 5

what are 2 important things to note about the nerves?

1. cutaneous innervation for a nerve is distal to the muscles supplied by the same nerve

2. coracobrachialis is innervated by musculocutaneous nerve but is actually a shoulder flexor.

name 1.

C5

name 2

C6

name 3

T2

name 4

T3

name 5

C5 ventral cutaneous branch

name 6

Axillary nerve

name 7

T2 lateral cutaneous branch

name 8

T3 lateral cutaneous branch

name 9

brachiocephalic nerve

name 10

musculocutaneous nerve

name 11

ulnar nerve

name 12

radial nerve

name 13

ulnar nerve

name the bones involved and the movement(s) that can occur normally in the shoulder

Bones: scapula and humerus

Movement: extension and flexion

name the bones involved and the movement(s) that can occur normally in the elbow

Bones: broad distal condyles of humerus, concave articular surfaces of ulna and radius

Movement: cranially-caudally

name the bones involved and the movement(s) that can occur normally in the carpus

bones: 2 rows, 3 joints (antebrachiocarpal, middle carpal and carpometacarpal)

Movements: Antebrachiocarpal and middle = hinge joints

Carpometacarpal = sliding joint

Extension/over-extension in dogs and cats, some adduction and abduction in primates.

Pigs, ruminants and horses - only flexion and extension

name the bones involved and the movement(s) that can occur normally in the metacarpo-phalangeal joint

Bones: metacarpals and phalanges

Movements: flexion through to hyperextension, abduction and adduction in primates.

name the bones involved and the movement(s) that can occur normally in the proximal interphalangeal joint

Bones: proximal phalanx and middle phalanx

Movement: extension and flexion only

name the bones involved and the movement(s) that can occur normally in the distal interphalangeal joint

Bones: middle and distal phalanges

movement: extension and flexion

name the extensor muscles of the shoulder

• brachiocephalicus (if limb isn’t weight bearing)

• biceps brachii

• supraspinatus

name the muscles that stabilise the shoulder

• supraspinatus

• infraspinatus

• subscapularis

• coracobrachialis

name the muscles that flex the shoulder

• trapezius (elevates)

• rhomboideus (draws dorsally)

• deltoideus

• teres minor

• teres major

• long head of triceps brachii

Name the muscles that extend the elbow

• triceps brachii

• anonceus (tenses joint capsule during extension)

• tensor fasciae antebrachii

• SDF

• DDF manica

name the muscles that flex the elbow

• brachialis

• biceps brachii

• coracobrachialis

• brachialis

Name the muscles that enable extension of the carpus

• extensor carpi radialis

• common digital extensor

• lateral digital extensor

• ulnaris lateralis

• extensor carpi obliquus

Name the muscles that flex the carpus

• ulnaris lateralis

• flexor carpi ulnaris

• superficial flexor manica

• deep digital flexor manica

name the muscles involved in extension of the digits

• extensor carpi radialis

• common digital extensor

• lateral digital extensor

name the muscles involved in the flexion of the digits

• superficial digital flexor manica

• deep digital flexor manica

Name some species differences in the scapula

Dogs: acromion process is absent, supraglenoid tubercle is part of the glenoid cavity, no glenoid notch

Horses: narrow supraspinus fossa, absent acromion, prominent tuber spine, SGT separate from glenoid cavity. Has a glenoid notch

Ruminants: Broad dorsal and larger infraspinous fossa, blunt acromion, doesn’t reach glenoid cavity, tuber spine is less present/absent. Indistinct glenoid notch

Birds: not flattened, only one supraspinous fossa?

Pig: rounded cranial margin, poorly defined acromion, prominent tuber.

Name some species differences in the humerus:

Dogs: single greater tubercle and supratrochlear foramen

Horses: greater tubercles are level with eachother, lesser tubercle is similar in size. Supratrochlear foramen is absent, very prominent deltoid tuberosity. Doubler intertubercular groove

Ruminants: cranial and caudal greater tubercles are higher than head. Greater tubercle overhangs intertubercular groove medially. Single intertubercular groove. Circular infraspinus insertion area. Small deltoid tuberosity. No supratrochlear foramen

Birds: ovoid head for articulation with scapula, coracoid and clavivle. Pneumatic bone.

Pig: greater tubercle has cranial and caudal parts higher than humerus head, rounded shape, almost encloses (single) intertubercular groove, no supratrochlear foramen

name some species differences in the radius and ulna

Dogs and cats: 2 separate bones, rotation is possible

Horse: proximal ulna present only, distally fused with radius. No rotation possible

Ruminants: 2 complete bones, fuse as animal ages, no rotation

Birds: ulna is thicker and longer, radius lying laterally to ulna

Pig: 2 separate bones, same diameter, no interosseus space, no rotation

Name some species difference in carpal bones

Carpal bones: radial and intermediate are fused, ulna is larger and has a different shape, all 4 in distal row

Horse: distal row: 1st is very small by second. 3rd and 4th span the rest of thwidth.

Bovine: distal row: no 1st carpus, 2nd and 3rd are fused, 4th present.

Pig: has 4, with increasing size (1-4)

Birds: carpus of the adult only has the ulnar and radial.

Name some species difference in metacarpal bones

Dog: 5 metacarpal bones

Horse: only the 3rd, with the 2nd and 4th present as vistigial.

Ruminants: third and fourth are fused with the 5th being a small button/visitigial bone

Birds: A single bone, a fused bone of metacarpal 1-3.

Pig: 4 metacarpals, 5th is absent.

which is the only animal to have 4 tricep heads?

dog

how does the horses deltoideus differ from other species?

• no acromial division

Why do horse muscles tend to be larger and longer?

• larger animal

• more robust muscle development for weight bearing

• powerful limb contraction needed

what is the synsarcosis

• where parts of the skeleton e.g. shoulder form a union to the rest of the skeleton via muscles alone.

what muscles do you expect to atrophy most in a dog with elbow disease/a painful elbow and why?

• triceps major

• brachialis

• muscles that are most vulnerable to atrophy are anti-gravity that cross a single joint.

How could we investigate forelimb lameness?

• palpation (swelling, localised head, asymmetry)

• walk/trot

• obeserve gait and movement

• radiography

• ultrasound

Name 3 examples of conditions which are generally called ‘elbow dysplasia’

1. ununited anconeal process (UAP)

2. osteochondrosis dissecans (OCD) of humeral condyle

3. fragmented coronoid process (FCP)