NMSK 3 - Introduction to the Forelimb

Identify bones forming the forelimb.

Scapula

Humerus

Radius

Ulna

Carpal bones

Metacarpal bones

Proximal, middle, and distal phalanges

Identify the bony landmarks of the forelimb.

1. Wings of atlas

2. Spine of scapula

3. Acromion

4. Greater tubercle of the humerus

5. Deltoid tuberosity

6. Olecranon

7. Lateral condyle of the humerus

8. Accessory carpal bone

List the features of the scapula.

1. Cranial angle

2. Spine of scapula

3. Supraspinatus fossa

4. Infraspinatus fossa

5. Neck

6. Supraglenoid tubercle

7. Infraglenoid tubercle

8. Caudal angle

9. Coracoid process

10. Glenoid cavity

List the features of the humerus.

1. Greater tubercle

2. Head

3. Lesser tubercle

4. Teres major tubercle

5. Deltoid tuberosity

6. Lateral supracondylar crest

7. Olecranon fossa (supratrochlear foramen in dogs)

8. Medial epicondyle

List the features of the radius and ulna.

1. Olecranon

2. Anconeal process

3. Trochlear notch

4. Lateral and medial coronoid processes

5. Distal articular facet for radius

6. Lateral styloid process

7. Articular facet for ulna

8. Medial styloid process

9. Articular circumference

List the features of the distal limb in the dog.

1. Accessory carpal bone

2. Ulnar proximal carpal bone

3. Radial proximal carpal bone

4. 1st of the distal row of carpal bones

5. 4th of the distal row of carpal bones

6. Sesamoid bone (within tendon of flexor carpi ulnaris muscle)

7. Proximal sesamoid bones

8. Dorsal sesamoid bones

9. Axis of manus

List the features of the forelimb of the horse.

A. Scapula

B. Humerus

C. Ulna

D. Radius

1. Scapula cartilage

2. Spine of scapula

3. Tuberosity of scapula spine

4. Supraglenoid tubercle

5. Supraspinous fossa

6. Infraspinous fossa

7. Head of humerus

8. Cranial part of greater tubercle of humerus

9. Caudal part of greater tubercle of humerus

10. Deltoid

11. Condyle

12. Olecranon fossa

13. Olecranon

14. Tubercle for lateral collateral ligament

15. Interosseous space

16. Lateral styloid process of radius

17. Accessory carpal bone

18. Proximal row of carpal bones

19. Distal row of carpal bones

20. Third metacarpal bone

21. Splint bone

22. Proximal sesamoid bones

23. Proximal phalanx

24. Middle phalanx

25. Distal phalanx

Identify features of the shoulder on a radiograph.

1. Spine of scapula

1'. Acromion

2. Supraglenoid tubercle

3. Greater tubercle of humerus

4. Head of humerus

Identify features of the elbow on a radiograph.

1. Humerus

1'. Medial epicondyle

2. Radius

3. Ulna

3'. Olecranon

3''. Apophysis of tuber olecrani

4. Anconeal process

Identify the joints forming the forelimb, and their main features (bones involved, type of joint, and range of motion).

Shoulder joint between the scapula and humerus

- Synovial, ball-and-socket

- Flexion, extension, abduction, adduction, and rotation

Elbow joint between the humerus, radius, and ulna

- Synovial, hinge

- Flexion and extension

- Pronation and supination

Carpal joints:

- All synovial

- Flexion, extension, and some abduction and adduction

Antebrachiocarpal joint between the radius, ulna, and proximal carpal bones

Intercarpal joint between proximal and distal carpal bones

Carpometacarpal joint between the distal carpal bones and metacarpal bones

Metacarpophalangeal joint between the metacarpal bones and proximal interphalangeal bones

- Synovial, hinge

- Flexion and extension

Proximal interphalangeal joint between the proximal and middle phalanges.

- Synovial, saddle

- Flexion and extension

Distal interphalangeal joint between the middle and distal phalanges.

- Synovial, saddle

- Flexion and extension

Describe the main muscle groups of the forelimb.

Extrinsic muscles

The forelimb is attached to the body by extrinsic muscles, which can be divided into 3 groups:

Protractor group

- Brachiocephalicus

- Omotransversarius

- Trapezius muscles

Retractor group

- Deep pectoralis

- Latissimus dorsi

Thoracic sling group (on medial side of forelimb)

- Serratus ventralis

- Deep pectorialis

- Rhomboideus

Intrinsic muscles do not hold the forelimb onto the body:

Extensors of the elbow, carpus, and digits are supplied by the radial nerve

Flexors of the carpus and digits are supplied by the medial and ulnar nerves.

Describe the extrinsic muscles of the proximal forelimb.

Brachiocephalicus

- 3 muscles:

- Action: protraction

- Innervation: accessory nerve

- Origin: back of the skull

- Insertion: medial side of humerus

Omotransversarius

- Action: protraction

- Innervation: accessory nerve

- Origin: transverse processes of atlas

- Insertion: acromion of scapula

Trapezius

- 2 parts: cervical and thoracic

- Action: protraction

- Innervation: accessory nerve

- Origin: midline

- Insertion: spine of scapula

Latissimus dorsi

- Action: retraction

- Innervation: brachial plexus

- Origin: dorsal midline

- Insertion: teres tuberosity of humerus

Deep pectoralis

- Action: retraction

- Innervation: brachial plexus

- Origin: sternum

- Insertion: medial side of humerus

Serratus ventralis

- Action: protraction and retraction

- Innervation: brachial plexus

- Origin: scapular

- Insertion: thoracic vertebrae and ribs

Rhomoideus

- Action: retraction

- Innervation: brachial plexus

- Origin: cranial thoracic vertebrae

- Insertion: dorsal scapular

Describe the intrinsic muscles of the thoracic limb acting on the shoulder joint.

Scapula muscles:

Supraspinatus

- Action: extension of shoulder joint and stability

- Innervation: suprascapular nerve

- Origin: supraspinous fossa of scapula

- Insertion: greater tuberosity of humerus

Infraspinatus

- Action: flexion of shoulder joint, and abductor of the humerus

- Innervation: suprascapular nerve

- Origin: infraspinous fossa of scapula

- Insertion: greater tubercule of humerus

Subscapularis

- Action: extension and adduction of the shoulder joint

- Innervation: subscapular nerve

- Origin: subscapular fossa

- Insertion: lesser tubercle of humerus

Shoulder muscles:

Deltoideus (draws the humerus back)

3 parts: scapular part, acromial part, and clavicular part.

Action: flexion of shoulder joint

Innervation: axillary nerve

Origin: scapular spine

Insertion: deltoid tuberosity of humerus

Teres major (draws the humerus back)

Action: flexion of shoulder joint

Innervation: axillary nerve

Origin: scapula

Insertion: teres major tuberosity

Describe the intrinsic muscles of the forelimb acting on the elbow joint.

Triceps brachii

- 3 heads, 4 in a dog

- Action: extension

- Innervation: radial nerve

- Origin: scapula and humerus

- Insertion: olecranon of the ulna.

Biceps brachii

- Action: flexion

- Innervation: musculocutaneous nerve

- Origin: supraglenoid tubercle of scapula

- Insertion: radial and ulnar tuberosity.

Brachialis

- Action: flexion

- Innervation: musculocutaneous nerve

- Origin: caudal humerus

- Insertion: medial on radius or ulna

Describe the intrinsic muscles of the forelimb acting on the carpal and digital joints.

Carpal muscles:

Flexor carpi radialis

Action: flexion of carpal joint

Innervation: medial nerve

Flexor carpi ulnaris

Action: flexion and abduction of forepaw

Innervation: ulnar nerve

Extensor carpi radialis

Action: extension of the carpal joint

Innervation: radial nerve

Extensor carpi ulnaris

Action: extension of carpal joint

Innervation: radial nerve

Digital muscles that have tendons extending to digits:

Superficial digital flexor

Action: flexion of the paw

Innervation: medial nerve

Deep digital flexor

Action: flexion of the paw

Innervation: medial nerve

Common digital extensor

Action: extension of the digits

Innervation: radial nerve

Lateral digital extensor

Action: extension of the digits

Innervation: radial nerve

List the ligaments of the forelimb.

Shoulder: poorly invested in ligaments due to its mobile nature

- Medial glenohumeral ligament

- Lateral glenohumeral ligament

Elbow: well supported by strong collateral ligaments

- Oblique ligament runs along the cranial surface of the elbow joint from the humerus, to join the medial collateral ligament.

- Medial collateral ligament

- Annular ligament holds the head of the radius against the ulna on species which can pronate/supinate

Carpal joint complex: many linking the carpal bones, distal antebrachium, and proximal metacarpus.

- Paired ligaments linkinking the accessory carpal bone to metacarpals IV and V to aid carpal flexion.

- Palmar carpal ligaments in horses, extending distally to form the carpal accessory (check) ligament which supports the DDFT.

Metacarpophalangeal and interphalangeal joints: strong collateral ligaments to maintain joint alignment.

Describe the formation and location of the brachial plexus.

- A major network of nerves located in the region of the axilla, from which peripheral nerve trunks of the forelimb are derived.

- Formed by the ventral roots of C5/C6 to T1/T2 spinal nerves.

- Located

Describe the nerves leaving the brachial plexus, in terms of the muscles and areas of the skin that they supply.

Suprascapular nerve

Origin: cranial part of brachial plexus, C6 and C7

Route: laterally round the cranial aspect of the neck of the scapula

Motor innervation: supraspinatus and infraspinatus

Sensory innervation: none

Subscapular nerve

Origin: cranial part of brachial plexus, C6 and C7

Route: direct to muscle

Motor innervation: subscapularis

Sensory innervation: none

Musculocutaenous nerve

Origin: middle part of brachial plexus, C7 and C8

Route: medial aspect of the limb, close to medial nerve

Motor innervation: biceps brachii, brachialis, coracobrachialis

Sensory innervation: dorsomedial aspect of forelimb

Axillary nerve

Origin: middle brachial plexus, C7 and C8

Route: behind the shoulder joint

Motor innervation: shoulder flexors

Sensory innervation: dorso-lateral aspect of proximal limb

Radial nerve

Origin: caudal brachial plexus, C7 and T2

Route: through the triceps and around the humerus to the lateral aspect of the forearm

Motor innervation: extensors of the elbow, carpus, and digits

Sensory innervation: craniallateral and medial forearm in dogs, lateral forearm in horses

Median and ulnar nerves

Origin: caudal brachial plexus, C8, T1, and T2

Route: along the medial aspect of the limb

Motor innervation: flexors of the carpus and digits

Sensory innervation: caudal aspect of the limb

Identify the structures in the diagram of the cervical and thoracic muscles

1. Sternocephalicus

2. Brachiocephalicus (cleidocephalicus and cervical part)

2'. Brachiocephalicus (cleidobrachialis part)

3. Omotransversarius

4. Superficial cervical lymph node

5. Trapezius (cervical)

5'. Trapezius (thoracic)

6. Deltoideus

7. Latissimus dorsi

8. Long head of triceps brachii

8'. Lateral head of triceps brachii

9. Superficial pectorals

10. Accessory axillary lymph node

Identify the structures in the diagram of the forelimb of the muscles in the elbow joint

1. Rhomboideus

2. Teres major

3. Supraspinatus

4. Scapula part of deltoid

4'. Acromial part of deltoid

5. Latissimus dorsi

6. Long head of triceps brachii

6'. Lateral head of triceps brachii

7. Brachiocephalicus (cleidobrachialis)

8. Brachialis

Identify the structures highlighted in the proximal forelimb

1. Trapezius

2. Latissimus dorsi

3. Omotransversarius

4. Scapula part of deltoid

4'. Acromial part of deltoid

5. Brachicephalicus (cleidocephalicus)

6. Triceps brachii

Identify the structures highlighted.

1. Latissimus dorsi

2. Teres major

3. Subscapularis

4. Supraspinatus

Identify the structures in the diagram of the distal limb.

1. Extensor carpi radialis

2. Common digital extensor

3. Lateral digital extensor

4. Extensor carpi ulnaris

5. Flexor carpi ulnaris

6. Long abductor muscle

7. Extensor retinaculum

8. Carpal pad

Identify the highlighted structures.

1. Extensor carpi radialis

2. Common digital extensor

3. Lateral digital extensor

4. Extensor carpi ulnaris

Identify the highlighted structures.

1. Superficial digital flexor

2. Flexor carpi radialis

3. Pronator teres

4. Extensor carpi radialis

List the nerves supplying the intrinsic muscles of the forelimb.

Suprascapular

- Supraspinatus

- Infraspinatus

- Subscapularis

Subscapular

- Subscapularis

Axillary

- Deltoids

- Teres major

Musculocutaneous

- Biceps brachii

- Brachialis

Radial

- Triceps brachii

- Extensor carpi radialis

- Extensor carpi ulnaris

- Lateral digital extensor

- Common digital extensor

Median

- Flexor carpi radialis

- Superficial digital flexor

- Deep digital flexor

Ulnar

- Flexor carpi ulnaris

List the nerve suppling the extrinsic muscles of the forelimb.

Accessory

- Brachiocephalicus

- Omotransversarius

- Trapezius

Brachial plexus

- Latissimus dorsi

- Deep pectorals

- Serratus ventralis

- Rhomboids

Describe the main arteries supplying the forelimb.

- The subclavian artery enters the forelimb via the axilla, where it becomes the axillary artery

- Number of branches continuing distally along the medial aspect of the limb.

- Brachial artery becomes the median artery

- Radial artery continues down into the palmar arteries.

Describe the main veins supplying the forelimb.

- Cephalic vein is located on the palmer aspect of the metacarpus

- Remains on the craniomedial aspect of the limb

- Passes the shoulder joint and heads towards the midline

- Drains into the jugular vein.

- Axillary vein becomes the brachial vein, which becomes the median vein

What blood vessel is used for venous access in the forelimb?

Cephalic vein

What blood vessel is used for assessing pulse in the forelimb?

Radial artery (digital artery branches)