Forelimb Flashcards
1
Q
Locomotor system
A
Musculoskeletal system that allows wide range of animal movement
Components
- Bones - act as rigid support
- Joints - allow movement between bones
- Muscles - produce movement between bones
2
Q
Cursorial adaptation of locomotor system
A
1) Reduced pectoral skeleton
- Allows more cranial/caudal movement
2) Elongation at proximal end of limb - scapular lies laterally
3) Elongation at distal end of limb - long metacarpals, walk on toes or hooves
3
Q
Reduced pectoral skeleton
A
In cursors clavicle is usually absent or vestigial
- No skeletal component attaching forelimb to trunk
- This type of joint is purely muscular - SYNOSARCOSIS
- This particular joint is the OMOTHORACIC JUNCTION
4
Q
Elongation at proximal end of limb
A
Scapula lies laterally
Stride length is increased by increasing the leg length.
- At proximal end of forelimb, the scapula moves from lying flat against the back of a broad chest, to lying flat against the sides of a deep narrow chest
5
Q
Elongation at distal end of limb
A
Long metacarpals, walk on toes/hooves
6
Q
Interaction between limbs and trunk
A
Folding limb = flexion
Moving limb forwards = protraction
Stretching limb = extension
Moving limb backwards = retraction
7
Q
Link between locomotion and diet
A
Locomotion and diet are linked in evolution
Herbivores with roughage diets and bulky abdominal viscera have less flexible trunks and rely more on limbs elongation
Horse:
- Relatively rigid vertebral column
- Most of propulsion/stride length results from limbs
- Fixed suspension phase
Carnivores with small volume, consuming meat diet
- Run fast
- Flexible trunks, multipurpose limbs
Cat:
- Flexible vertebral column, allowing limbs to swing more
- Acts like bow to increase propulsion/stride length from limbs
- Flexed + extended suspension phases
8
Q
Axial skeleton
A
Bones of vertebral column, skull and ribcage
9
Q
Appendicular skeleton
A
All bones of fore and hindlimbs
10
Q
Bone types
A
1) Flat (scapula/pelvis)
- Large SA for muscle attachment
- Protection of underlying structures
2) Long (humerus/femur)
- Support + leverage in limbs
3) Short (carpus/tarsus)
- Large range of movement
- Anti-concussive
4) Sesamoid bones
- Embedded in tendons
- Change in angle over bony surface
- Redirect forces
- Reduce friction to prevent damage
11
Q
General features of bones
A
1) Smooth surface area
- Passage of structures/tendons
- Articular surfaces
2) Specific bony contours
- Tuberosities/tubers/tubercles
- Provide site for attachment of structures
3) Rough surface areas
- General muscle attachment
12
Q
Visible features of long bones on radiographs
A
Diaphysis = shaft
Cortex = wall
Medullary cavity = hollow centre
Epiphysis = end
Metaphysis = transition zone
13
Q
Bone growth
A
Short/sesamoid bones:
- Usually 1 centre of ossification per bone
Flat/long bones:
- Usually more than one centre per bone
Attachment sites for important structures may have a separate centre
Cartilage between centres appears black on radiographs = physis/growth plate
14
Q
Clinical significance of growth plates
A
Young animal:
- Open phases/growth plates
- Produce increase in bone length
Mature animal:
- Closed growth plates = physeal scars
- Time of closure depends on contribution of specific physis to limb length
- Can estimate age from growth plate closure times
Adult dogs:
- Shaft is weakest point = fractures
Young dogs:
- Growth plate weakest = damage/separation
- Can cause premature closure of growth plate
15
Q
Skeletal muscle
A
Individual muscle fibres
Arranged in parallel lines
Collected into bundles
Covered by fibrous tissue
- Deep fascia
Attached to rigid structures
- Usually bone
Origin - usually proximal
Insertion - usually distal
16
Q
Skeletal muscle classification
A
Intrinsic muscles
- Origin + insertion within appendicular skeleton
- Movement of limb joints
- Flexion and extension
Extrinsic muscles
- Origin on axial skeleton
- Insertion in appendicular skeleton
- Movement of limb relative to trunk
- Protraction + retraction of limb
17
Q
Regions of the forelimb
A
Omo - shoulder
Brachium - arm
- Region from shoulder to elbow
Antebrachium - forearm
- Region from elbow to carpus
Carpus - wrist
Manus - hand
- Region distal to carpus
Digit - toe
18
Q
Scapula
A
Type of flat bone
Body
Neck
Glenoid cavity
- Articular surface (shoulder joint)
- Concave
- Smooth surface
Supraglenoid tubercle
- Attachment of biceps brachii m.
Lateral surface:
- Spine
- Supraspinous fossa
- Infraspinous fossa
- Acromion process
Medial/costal surface:
- Serrated
- Rough bone
- Attachment of:
- Serratus ventralis m. (D)
- Subscapularis m. (V)
19
Q
Scapula of cat
A
More rounded cranial angle than dog
Suprhamate process
- Proximal to acromion process
20
Q
Scapula development
A
Centres of ossification - 2
- Body
- Supraglenoid tubercle
Potential problem
- Tendon of origin of biceps brachii m.
- Physis weak point = avulsion fracture
21
Q
Scapula palpation
A
Can palpate:
- Dorsal border
- Cranial border
- Cranial angle
- Spine
- Acromion
- Guide for locating shoulder joint
- Caudal border (beneath muscle)
22
Q
Brachiocephalic muscle
A
Extrinsic muscle
Origin = cervico-thoracic fascia
Insertion = humerus (aponeurosis)
Function - protractor
Parts of m.
- Cleidocervicalis
- Cleidomastoideus
- Cleidobrachialis
23
Q
Omotransversarius m.
A
Extrinsic muscle
Origin = transverse wing of atlas (C1)
Insertion = acromion process
Function - protracts the limb
24
Q
Latissimus dorsi m.
A
Extrinsic muscle
“broadest muscle of the back”
Origin = thoracolumbar fascia
Insertion = humerus (aponeurosis)
Function - retractor
25
Serratus ventralis m.
Located between forelimb and trunk
Origins:
- Thoracic wall (ribs)
- Cervical vertebrae
Insertions:
- Proximal scapula (medial)
- Proximal to pivotal point
Functions:
- Cranial portion - retractor
- Caudal portion - protractor
(no effect on shoulder)
26
Abductor muscles
Extrinsic
Move limb away from midline
- Muscles located proximal to pivotal point and limb
27
Adductor muscles
Extrinsic
Move limb towards midline
- Located distal to pivotal point and medial to limb
- Limited movement
28
Trapezius m.
Extrinsic
Origin = cervicothoracic fascia
Insertion = proximal scapular spine
Cranial + caudal part
No effect on shoulder
29
Rhomboideus m.
Extrinsic
Lies deep to trapezius
Origin = cervicothoracic fascia
Insertion = dorsal border of scapula
Abductors of limb
No effect on shoulder
30
Pectoral muscles
Extrinsic
Origin = sternum
Insertion = humerus
2 heads: deep + superficial
Adductor of limb
31
Intrinsic muscles
Both origin + insertion within appendicular skeleton
No effect on limb relative to trunk
Move joints within limb
- Flexion
- Extension
32
Humerus
S shaped long bone
Proximal end:
- Head (articulates with glenoid cavity @ shoulder joint)
- Greater tubercle - lateral aspect
- Lesser tubercle - medial aspect
- Intertubercular groove
- Smooth bone surface
- Tendon of origin of biceps brachii m. passes through this structure
Distal end:
- Olecranon/ulnar fossa (caudal)
- Radial fossa (cranial)
- proximal to articular surfaces
- Supratroclear foramen:
- nothing passes through
- may not be present in short legged dogs
Centres of ossification: 5
- Proximal epiphyses = 1
- Body - 1
Condyle:
- Medial epicondyle
- Medial half of the condyle
- Lateral half of the condyle
Palpation landmarks
- Greater tubercle (guide for locating shoulder joint)
- Lateral epicondyle
- Medial epicondyle
33
Humerus of cat
Proximal end same as dog
Distal end:
- Olecranon fossa
- Radial fossa
- No supratrochlear foramen
- Suprachondyloid foramen
- Brachial artery
- Median nerve
- Vulnerable in fractures
34
Peripheral nervous system (forelimb)
- Cranial nerves
- Spinal nerves
35
Spinal nerves
Leave spinal cord
Intervertebral foramen
Paired left and right
Branches
- Dorsal branches supply dorsal structures
C6, C7, C8, T1, T2
Ventral branches of these nerves form brachial plexus located in axillary region
- Emerging nerves supply forelimb
- some extrinsic + all intrinsic
- Motor = efferent fibres
- Sensory = afferent fibres
- Spinal reflexes
36
Nervous system in forelimb
Efferent supply:
- Carry impulses from brain to structure
- Motor nerve fibres
Afferent supply:
- Carry impulses from structure to brain
- Sensory nerve fibres
- Proprioception - location of limb in space
Mixed nerves:
- Consist of both motor and sensory fibres and transmit messages in both directions at once
- Spinal reflexes
37
Brachial plexus
Suplies all intrinsic muscles
Supplies some extrinsic muscles
Latissiumus dorsi (retractor)
Serratus ventralis (protractor + retractor)
Pectorals (adductor)
Does not supply:
- Brachiocephalicus (protractor)
- Trapezius + rhomboideus (abductors)
38
Joints
Between every bone in skeleton
Fibrous:
- Little movement
- e.g skull sutures
Cartilaginous:
- Little movement
Synovial
39
Synovial joint
Allows large range of motion between bones
Most limb joints
40
Features of synovial joints
Hyaline cartilage
- Covers articular surfaces
- Reduce friction, flexible joint
- Avascular (no vessels)
- No nerve endings
Synovial fluid
- Viscous/sticky
- Nourishes cartilage
- Lubricates
Synovial membrane
- Produces synovial fluid
- Physical barrier to contain fluid
Joint capsule
- Fibrous layer
- Incorporates synovial membrane
- Attaches around osterochondrial junction
Ligament
41
Ligaments
Dense, fibrous connective tissue
Run from bone - bone
Collateral ligaments support joint (medial + lateral)
Function:
- Support joint, hold bones together
- Restrict movements b/w bones
42
Shoulder joint
Scapula - glenoid cavity
Humerus - head
Palpable landmarks:
- Acromion process (scapula)
- Greater tubercle (humerus)
All synovial joint features
- BUT poorly developed collateral ligaments at the lateral aspect
43
Bicipital bursa (shoulder joint)
Joint capsule extends into inter-tubercular groove
- Between greater + lesser tubercles
Wraps around tendon of origin of Biceps brachii (originates on supraglenoid tubercle of scapula)
Held in place by transverse ligament
44
Shoulder joint support
Lateral support:
- Supraspinatus m.
- O = supraspinus fossa
- I = greater tubercle
- Also extend shoulder joint
- Infraspinatus m.
- O = infraspinous fossa
- I = distal to greater tubercle
- Also abducts the shoulder
- N = suprascapular nerve - motor fibres only
Medial support
- Supscapularis m.
- O = sub scapular fossa
- I = lesser tubercle
- Also adducts the shoulder joint
- N = subscapular nerve - motor fibres only
45
Shoulder joint extensors
Cross cranial to shoulder joint
Brachiocephalicus
- Extrinsic muscle
- Also limb protraction
N = not from brachial plexus
Biceps brachii m. (1 head in dog)
- O = supraglenoid tubercle
- I = ulnar + radial tuberosities
- Intrinsic muscle
- Also allow elbow flexor/shoulder extensor
- Motor nerve supply: Musculocutaneous nerve
- Bicipital bursa
- Protects tendon of origin
- Intertubercular groove
- Transverse ligament
46
Shoulder joint flexors
Cross caudal to shoulder joint
Latissimus dorsi
- Extrinsic muscle
- Also limb retraction
- Nerve supply from brachial plexus
Teres Major
- O = caudal border of scapula
- I = medial humerus
- Nerve supply:
- Axillary nerve
- Motor + sensory fibres
Teres Minor
- Overlies lateral aspect joint space
Deltoids muscle
- 2 heads
- O = scapular spine + acromion process
- I = lateral aspect of humerus
- Intrinsic muscle
- Nerve supply:
- Axillary nerve
- Mixed type (M+S fibres)
Triceps muscle
- 4 heads
- Long head
- O = caudal border scapula
- 2 parts
- I = olecranon of ulna
- Also elbow extensor
- Nerve supply:
- Radial nerve
- Motor + sensory fibres
47
Shoulder extensors
Cranial to shoulder
Brachiocephalicus
Biceps brachii
48
Shoulder flexors
Caudal to shoulder
- Latisimus dorsi
- Deltoeus
- Teres major
- Triceps - long head
49
Radius + ulna
Long bones
Paired + crosses each other obliquely
Ulna - longer and leverage
Radius - shorter and main weight bearing
50
Radius
Proximal end:
- Head - fovea captitis (articular surface/elbow joint)
- Neck
Body
Distal end
- Trochlea - articular surface (carpus)
- Styloid process
- Medial
- Attachment medial collateral ligament of carpus
- Ulnar notch
51
Ulna
Proximal end:
- Olecranon process
- Anconeal process
- Beak shaped
- Fits into olecranon/ulna fossa of humerus
- Troclear notch
- Articular surface (elbow joint)
- Lateral coronoid process
- Medial coronoid process
- Radial notch
- Articulates with radius
Body
Distal end:
- Styloid process
- Attachment lateral collateral ligament of carpus
52
Proximal articulation of radius + ulna
Radius (head)
Radial notch of ulna
Held by annular ligament
- Runs lateral to medial coronoid process
- Rotation possible
53
Distal articulation of radius + ulna
- Fibrous joint
- Some rotation possible
- Interosseous space:
- Between bodies
- Interosseous ligament
- Fibrous joint
54
Evolution of radius + ulna
Toes rotated cranially
Elbows rotated caudally
Radius + ulna then rotate around eachother
Proximal:
- Ulna most medial projection
Distal:
- Ulna most lateral projection
55
Palpation of radius + ulna
Ulna:
- Olecranon process
- Lateral styloid process
Radius:
- Medial styloid process
Cat:
- Square olecranon
- Radius + ulna similar diameter
56
Development of radius + ulna
Radius (growth plates):
- Proximal epiphyses
- Body
- Distal epiphyses
- Total = 3
Ulna:
- Olecranon process
- Anconeal process
- Body
- Distal epiphyses - conical shape
- Total = 4
57
Elbow joint
Humerus - radius + ulna
- Complex joint
Humerus:
- Trochlea
- Articulates with trochlea notch of ulna + fovea capitis of radius
- Capitulum:
- Articulates only with fovea capitis of radius
Extensive joint capsule
- Osteochondral junction
- Incorporates proximal radio-ulnar articulation
Stability:
- Collateral ligaments
- Humerus - radius + ulna
- Bony structures:
- Anconeal process (ulna)
- Olecranon/ulna fossa (humerus)
58
Elbow joint - movement
Limited to flexion + extension
Ulna acts as lever
Elbow extensors insert onto olecranon
- Avulsion possible
Joint between radius + ulna:
- Rotation possible
- Annular ligament
- Interosseous ligament
- Fibrous joint distally
- Supination
- Pronation
- Dogs - rotation limited
- Cats - large amount of rotation
59
Elbow extensors
Caudal to elbow joint, insert onto olecranon process
Triceps muscle (4 heads)
i) Long head
- O = caudal border of scapula (also shoulder flexor)
ii) Lateral head
- O = lateral aspect humerus
iv) Accessory head
(ii, iii, iv - no effect on shoulder)
Motor nerve supply - radial nerve
60
Elbow flexors
Cranial to elbow joint
Biceps brachii muscle
- O = supraglenoid tubercle
- I = proximal radius
(also shoulder extensor)
Brachial muscle
- O = caudal aspect humerus
- I = proximal radius
- Follows musculospiral/brachial groove
- Motor nerve supply: musculocutaneous nerve
61
Elbow rotators
Supinator muscle
- O = lateral epicondyle
- Radial nerve
Pronator teres muscle
- O = medial epicondyle
- I = proximal radius
- Median nerve
62
Forelimb supply
Limb naturally in extended position
Blood vessels cross flexor aspect of joints
Avoids stretching of vessels
Vein, arteries, nerves
Arterial supply:
- Oxygenated blood from heart to peripheral tissues
- Major vessel runs down limb
- Changes name according to region
63
Forelimb arterial supply
Subclavian artery
- Runs around 1st rib - axilla
Axillary artery
- Runs through axilla
Brachial artery
- Runs down brachium
- Branches
Median artery
- Runs down medial aspect antebrachium
- Branches - radial artery
- Terminates in superficial palmar arch
Superficial brachial artery
- Runs down cranial aspect antebrachium
64
Palmar blood supply
Median artery
- Superficial palmar arch
- Palmar common digital arteries
Caudal interosseous artery
- Deep palmar arch
- Palmar common/digital/metacarpal arteries
- Digital arteries
Palmar supplies fuse then branch resulting in arterial supply to each digit
- 4 vessels per digit
- Palmar supply most important
- Axial palmar proper digital A largest
- Implications when amputating toes
65
Dorsal blood supply
Superficial brachial artery
- Superficial dorsal supply to forepaw
- Dorsal common digital arteries
- Dorsal digital artery
66
Forelimb venous blood drainage
Veins
Deep system:
- Follows arterial supply
Superficial system:
- Cephalic vein
- Drains into jugular vein/vena cava
67
Carpus
Composed of carpal bones
- Short bones
Proximal row:
- Radial/intermediate carpal bone (fused)
- Ulnar carpal bone
- Accessory carpal bone
Distal row:
- 1st, 2nd, 3rd and 4th carpal bones
Carpus - development
- Single centre of ossification
- Except accessory carpal bone = 2
- Fused radial/intermediate carpal bone =2
68
Carpal joints
Antebrachio-carpal joint:
- Between antebrachium + carpus
- Between antebrachium + carpus
- Radius - RCB + UCB
- Ulna - UCB + ACB
Midle carpal joint:
- Proximal + distal rows
Carpo-metacarpal jont:
- Distal row + metacarpal bones
- Intercarpal joints
69
Carpal joints - movements
Standing position = extension
Large range of flexion
- Most movement antebrachio-carpal joint
- Least movement carpo-metacarpal joint
- Some movement between carpal bones
- ACB acts as level for distal limb
- Insertion of major carpal flexor muscle
- Counteraction by palmar ligament
70
Carpal joint - support
Typical synovial joint:
- Single joint capsule extending
- Proximally between metacarpal bones
- Distally between metacarpal bones
- Poor communications between compartments
Collateral ligaments:
- Lateral:
- Ulna to 5th metacarpal bone
- Medial:
- Radius to 2nd metacarpal bone
- Styloid processes vulnerable intracarpal ligaments
Palmar aspect:
- Fibrocartilagenous reinforcement of the joint capsule
Functions:
- Friction free surface for passage of tendons
- Passive maintenance of joint extension/prevention of collapse into hyperextension
Retinaculum
- Sleeve of deep fascia, encloses the carpal region both at palmar + dorsal surface:
- Attaches to lateral aspect of the Accessory carpal bone
- Crosses from ACB to medial aspect carpus
- From carpal canal
71
Carpal canal
Dorsal boundary:
- Fibrocartilagenous reinforcement of palmar aspect of carpal joint capsule
Lateral boundary:
- ACB
Palmar boundary:
- Palmar/flexor retinaculum
Dog:
- Deep digital flexor tendon through the tunnel/canal
- Blood vessels + nerves
- Superficial digital flexor tendon outside
72
Carpal joint palpation
- Accessory carpal bone
- Joint spaces (flexion)
- Medial styloid process (radius)
- Lateral styloid process (ulna)
73
Manus
Metacarpal bone
Digit
- Proximal phalanx
- Middle phalanx
- Distal phalanx
- Long bones
- Sesamoids
Dog + cat = digitigrade
- 4 weight bearing + 1 vestigial
- Numbered medial to lateral
1st digit = dew claw
- Vestigial
- Medial aspect
- Non-weight bearing
- Has 3 elements
- Commonly removed in puppies
74
Manus development
Centres of ossification
- MC (2): Body + proximal end
- PP (2): Body + proximal end
- MP (2): Body + proximal end
- DP (1)
75
Digit
Distal Phalanx (DP):
- Long bone - debate
- Ungual process
- Ungual crest
- Round root of claw
- Very vascular
- Extensor process
- Extensor tendons
- Palmar process
- Flexor tendons
76
Joints of manus
Metacarpo-phalangeal joint
Promimal interphalangeal joint (PIP)
Distal interphalangeal joint
- All typical synovial joints
- Flexion + extension
Stability:
- Collateral ligaments
- Sagittal ridge/groove
77
Metacarpo-phalangeal joint
2x proximal sesamoids
- Palmar aspect
- Either side of sagittal ridge
- Protect flexor tendons
1x dorsal sesamoid
- Protect extensor tendons
Resting position extended
Interosseous muscle + proximal sesamoids
Sling configuration - suspends MCP joint
Supported by metacarpal foot pad
78
Distal inter-phalangeal joint
Deep digital flexor tendon
Common digital extensor tendon
Dorsal elastic ligament:
- Proximal end (MP)
- Extensor process DP
Dog:
- Forces balanced to maintain tip of claw above horizontal
- Problem if DDFT severed
79
Manus - cat
Claws not visible:
- Very strong dorsal elastic ligament
- DIP joint hyperextended
- Claw rests in skin fold/sheath so not visible
- Remain sharp for hunting/climbing
Exposure of claws:
- DDFT flexes joint
- Manual pressure to digital pad
80
Muscles of antebrachium
Affects joints of carpus + digits
Muscle belly - antebrachium
Tendon of insertion - distal to carpus
Extensors of distal limb:
- O = lateral epicondyle of humerus
- Run over dorsal aspect carpus
- Radial nerve
Flexors of distal limb:
- O = medial epicondyle
- Run over palmar aspect carpus
- Median + ulnar nerves
81
Extension of carpus
O = lateral epicondyle
Innervation = radial nerve
Extensor carpi radialis m.
- I = metacarpal bones
Abductor pollicus longus/extensor carpi obliquus m.
- Crosses at level of carpus
- Sesamoid in tendon of insertion
- I = proximal end of metacarpal II
Extensor carpi ulnaris/ulnaris lateralis m.
- I = 5th metacarpal bone + ACB
- Flexion or extension depending on position of limb
82
Extension of carpus + digitalis
O = lateral epicondyle
I = radial nerve
Common digital extension m
- I = all digits
- Distal phalanx - extensor process
- Extends carpus and digits II to V
Lateral digital extensor m.
- I = 4th + 5th digits
- Distal phalanx - extensor process
- Extension of digit II, IV and V
83
Flexion of carpus
O = medial epicondyle
I = median + ulnar nerves
Flexor carpi ulnaris m.
- O = olecranon/epicondyle of humerus
- I = accessory carpal bone
Flexor carpi radialis m.
- I = metacarpal bones
84
Flexion of carpus + digits
O = medial epicondyle
I = median + ulnar nerves
Superficial digital flexor m.
- I = middle phalanx of all digit (II, III, IV, V)
- Runs out with carpal canal
Deep digital flexor muscle
- O - also radial + ulnar heads
- I - 3rd/distal phalanx of all digits
- Distal phalanx - palmar process
- Tendon runs through carpal canal
- Passes through SDFT
85
Footpads
Carpal/stopper pad:
- Protects accessory carpal bone
Metacarpal pad x1 (heart shaped):
- Overlies MCP joints
Functions:
- Resistance to trauma
- Traction - prevent slipping
- Anti-concussive
- Protect deep structures
- Support digit
- Allow weight bearing over DP, MP, PP + MCP joints
86
Organisation of skin
Epidermis + dermis
Epidermis:
- Cells constantly produced by germinative layer
- Cells age as move outwards
- Dead at surface + slough
- Constant replacement
- No blood supply
- No nerve supply
- Active production of skin cells
87
Footpad modifications
Trauma resistance:
- Increased skin thickness
- Increased turnover of cells
- Active germination layer
- Deposition of keratin
- Hard proteinaceous material
- Keratinised stratified squamous epithelium
- Rough surface (conical papillae)
- Grip
- Sweat glands
- Heat loss
- Hairless, thick skin
88
Footpad components
Skin
- Epidermis
- Contains the germinative layer
- Dermis
Superficial fascia
Digital cushion
- Rich in fibroelastic tissue
- Fat
- Vascular supply
Function = shock absorption
Clinical considerations
- Wounds
- Elastic tissue
- Contains excessive vascular channels
- Sweat
- Bandaging
- Damage to DDFT
- stubbed toe
89
Claw
No superficial fascia
Dermis
- Fused directly to periosteum of ungual process of DP
Germinative layer
- Active in n2 areas only
Stratum tectorum
- Waterproof surface layer
- Produced by skin in ungual recesses
Tip touches ground
Position maintained by:
- Extensor tendons
- Dorsal elastic ligament
- Balanced by DDFT
Continuous growth
- Tip wears naturally
- Reduced wear
- Not walking
- Walking on soft ground
- Dew claw
- DDFT damage
Claw grows in circular fashion
- Can eventually grow into pan
90
Germinative areas (claw)
Germinative area 1:
- Recess between claw + skin
- Horn grows over dorsal + lateral surfaces of ungual process
- Horse shoe shaped in transverse section/short axis
Germinative area 2:
- Palmar surface of ungual process
- Horn covers palmar surface
91
Lymphatic system (paw)
Cardiovascular system
- Continuous system
- Leaky capillary bed
- Exchange of material
- Net loss
- Fluid accumulation
- Oedema/swelling in peripheral tissues
Lymphatic vessels
- Recovery/scavenging system
- Series of individual vessels
- Thin walled
- Run from periphery to thoracic duct
- Thoracic duct empties into caudal vena cava
- Transports lost material back into systemic circulation
Lymph nodes
- Filters
- Located where lymph vessels converge
- Prevent contaminants reaching systemic circulation
- Remove invading organisms
- Contain defence cells
92
Forelimb lymph nodes
Prescapular lymph node
Axillary lymph node
Enlarged in response to infection.
Can use to differentiate between localised/generalised disease
Important in large animals for meat inspection
93
Nerve supply (paw)
Brachial plexus supplies:
Selected extrinsic muscles:
- Pectoral muscles
- Latissimus dorsi
- Serratus ventralis
All intrinsic muscles:
- Subscapular nerve
- Suprascapular nerve
- Musculocutnaeous nerve
- Axillary nerve
- Radial nerve
- Median + ulnar nerve
94
Subscapular nerve
Motor nerve - no cutaneous sensation
Medial shoulder support
- Subscapularis m.
95
Suprascapular nerve
Motor nerve - no cutaneous sensation
Lateral shoulder support
- Supraspinatous m.
- Infraspinatous m.
96
Musculocutaneous nerve
Mixed nerve
Sensory:
- Cutaneous sensation to:
- Cranial + medial aspect of elbow
- Medial aspect of antebrachium
Motor:
- Elbow flexors
- Brachialis m.
- Biceps brachii m.
- Coracobrachialis m.
If damaged:
- No compensation
- Loss of elbow flexion
97
Axillary nerve
Mixed nerve
Motor supply:
- Dedicated shoulder flexors
- Deltoideus m.
- Teres major m.
Sensory fibres:
- Cutaneous sensation to:
- Lateral aspect shoulder + brachium
Damage - compensation by:
- Latissimus dorsi
- Long head of triceps
98
Median + ulnar nerve
Mixed nerve
Sensory fibres
- Cutaneous sensation to:
- Caudal + palmar aspect limb
- Dorsal aspect 5th digit
Motor supply:
- Carpal + digital flexors
- Flexor carpi ulnaris m.
- Flexor carpi radialis m.
- Superficial digital flexor m
- Deep digital flexor m.
Damage - no compensation
- Loss of distal limb flexion
99
Radial nerve
Mixed nerve
Sensory fibres:
- Cutaneous sensation to:
- Dorsal + cranial aspect limb
- Except dorsal aspect 5th digit
Motor supply
- Extensors of elbow
- Triceps m.
- Extensors of carpus + digits
- Extensor carpi radialis m.
- Extensor carpi ulnaris/ulnaris lateralis m.
- Common digital extensor m.
- Lateral digital extensor m.
100
Radial nerve - route
- Starts medial
- Passes caudal to shoulder
- Passes through triceps
- Supplies triceps
- Follows musculospiral groove
- Branch - lateral epicondyle
- Supplies distal limb extensors
- Branch - cranial/dorsal aspect of limb
- Runs alongside cephalic vein
- Supplies cutaneous sensation
- Humeral fracture most common cause of damage
- deficits depend on level of damage
101
Radial nerve damage
Motor losses
Proximal level:
- All extensor m. affected
- Can't extend elbow, carpus or digits
- Limb appears longer than opposite one
Distal level:
- Extensors of carpus + digits affected
- Can't extend carpus/digits
Triceps intact
- Can't extend elbow
- Can weight bear if limb extended
- Can learn to swing leg to compensate
102
Brachial plexus damage
Tear/avulsion = stretching
- High impact collision
- Head + neck one direction
- Limb the other direction
- Regeneration possible with time
- Mismatching may result in aberrant sensation
Tumour
- Effects depend on which nerves affected
Effect on limb:
- CAN protract/abduct limb
- Can't retract/adduct limb
- Can't extend/flex limb
- Can't weight bear
No cutaneous sensation on limb or lateral thorax to level of 3rd intercostal space
103
Equine forelimb
Unguligrade
Perissodactyla
Weight bearing distal phalanx of 3rd digit
Same bones
Same joints
Same muscles as dog
Manus expanded
- Don't confuse with antebrachium
104
Superficial structures of equine forelimb
Chestnut:
- Vestigial horn pad
- 1st metacarpal bone
Ergot:
- Horny lump in skin
- Palmar aspect MCP joint
- Hidden by hairs
- Remnant of metacarpal pad
105
Biceps brachii m. (equine)
Function = extends shoulder/flexes elbow
Origin = supraglenoid tubercle
- Separated from glenoid cavity
Insertion = proximal radius
Double tendon of origin
- Humerus
- Intermediate tubercle
- 2 inter-tubercular grooves
Bicipital bursa
- Separate from shoulder joint capsule
Lacerates fibrosis:
- Fibrous extension
- Joins extensor carpi radialis
- Inserts proximal MC3
- Maintains shoulder + carpus in extension
- Part of stay apparatus
106
Elbow joint (equine)
Radius + ulna fused
- No rotation
- No annular ligament
- Collateral ligaments present
Triceps only 3 heads
Bursa:
- Fluid filled cushion
- Protection of tendons
- Tricipital bursa
- Between tendon + olecranon process
- Subcutaneous bursa
- Between skin + tendon of insertion of triceps
Clinical significance:
- Capped elbow - poor bedding
- Deeper swelling - true bursitis
107
Carpus (equine)
Carpal bones:
- All present except 1st
- 3rd CP largest
Movement:
- Most at antebrachio carpal joint
- Lease carpometacarpal joint
- Collecting joint fluid samples
108
Carpus joint (equine)
Synovial joint
- Separates compartments
Support:
- Collateral ligaments
- Palmar ligament
- Palmar fibrocartilagenous plate:
- Origin of check ligament for DDFT
- Flexor reticulum
Carpal canal:
- Palmar fibrocartilagenous plate
- Palmar/flexor retinaculum
- Accessory carpal bone
(Dog: DDFT only)
Horse: both DDFT + SDFT
109
Tendon sheath (equine)
Protects tendon in confined spaces
Dorsal aspect:
- Surrounds extensor tendons
Carpal canal:
- 1 sheath for DDFT + SDFT
- Inflammation - increased pressure
- Throroughpin bulges proximally + distally
110
Metacarpal bones (equine)
3rd MC = cannon bone
Weight bearing
Distal articular surface
- Sagittal ridge
2nd + 4th metacarpal bones:
- Splint bones
- Vestigial - non-weight bearing
- Button at distal end - palpable
Joints between MCs:
- Fibrous joints (syndesmosis)
- Mineralise with age
- Splints
111
Phalanges (equine)
Proximal phalanx (P1)
- Long pastern bone
- Raised V on palmar surface
- Attachment oblique distal sesamoidean ligament
Middle phalanx (P2)
- Short pastern bone
Bony contours
- Attachement collateral ligaments - ringbone
112
Distal phalanx (P3) (equine)
Pedal/coffin bone
- Complex shape
- Extensor process
- Attachment common digital extensor tendon
- Palmar processes
- Support lateral cartilages
- Solar surface
- Attachment deep digital flexor tendon
Dorsal surface:
- Striations:
- Hoof attachment
- Blood vessels
- Vascular channel
(vs nutrient foramen)
113
Manus bone development (equine)
Centres of ossification:
MC 3:
- Body + distal epiphyses (2)
MC 2 + 4:
- Proximal epiphyses + body (2)
PP:
- Proximal epiphyses + body (2)
DP:
- Body (1)
114
Proximal sesamoids (equine)
No dorsal sesamoid
Proximal sesamoid bones:
- Triangular shaped
- Distal end MC3
- Either side of sagittal ridge
- Embedded in suspensory ligament (interosseous L)
Functions
- Protect SDFT and DDFT
115
Distal sesamoid (equine)
Navicular bone
- 2 flat articular surfaces
- Covered with hyaline cartilage
- Vascular channels
- Located palmar aspect DIP joint
- Dorsal surface
- Articulates with MP + DP
- Palmar surface
- Guides DDFT over DIP joint
- Under large amount of pressure
116
Metacarpo-phalangeal joint (MCP) (equine)
Fetlock
- MC3 and PP
- Synovial joint
- Extensive joint capsule
- Large dorsal pouch
- Protects extensor tendons
- Large palmar pouch
- Incorporates proximal sesamoids
- No dorsal sesamoid (c.f dog)
Natural position = extension
Limited to flexion + extension
- Sagittal ridge distal MC3
- Sagittal groove proximal PP
- Collateral ligaments
- MC - PP
Tendency to collapse into hyperextension
- Suspensory ligament
- Sesamoidean ligaments
117
Suspensory ligaments (equine)
Entirely ligamentous
Origin:
- Proximal palmar MC3
- Fills area between splint bones
Branches:
- Abaxial aspect proximal sesamoids
- Passes to dorsal aspect
- Fuses with common digital extensor tendon
Function:
- Prevent collapse of MCP joint during weight bearing
- Return MCP from hyperextension to normal extended position
- Relies on stability of proximal sesamoid bones
118
Carpal joints - support (equine)
Inter-sesamoidean ligament
- Reinforced fibrocartilage
- Proximal scutum (shield)
- Passage of DDFT + SDFT over sesamoids
Collateral sesamoidean ligaments:
- Proximal sesamoids - MC + PP
119
Sesamoiden ligaments 2 (equine)
1) Cruciate
2) Short
- Proximal sesamoids - PP
3) Oblique:
- Proximal sesamoids - PP
- V-shaped through on PP
4) Straight ligament:
- Proximal sesamoids - MP
- Inserts with SDFT
120
MCP Joint (equine)
Function relies on interaction between
- Suspensory ligament
- Proximal sesamoids
- Sesamoidean ligaments
- Common digital extensor tendon
121
Proximal Interphalangeal joint (PIP) (equine)
"Pastern" joint
Limited to flexion + extension
- Distal PP - sagittal groove
- Proximal MP - sagittal groove
- Collateral ligaments:
- Run from PP - MP
- Extension runs to navicular bone
122
Distal interphalangeal joint (DIP) (equine)
Coffin joint - buried in hoof
Components:
- Middle P + distal P
- Distal sesamoid + DP
- Distal sesamoid MP
Extensive joint capsule
- Forms bursa
- Protects extensor tendon
- Accessible for injection
Flexion + extension
- Sagittal ridge + groove
- Broad so some rotation possible to accommodate uneven ground
- Collateral ligaments (CL)
- MP - DP
- Movement
- Common digital extensor tendon
- Deep digital flexor tendon
- No dorsal elastic ligament in horse
123
Digital sesamoid (equine)
Ligaments of distal sesamoid:
- Collateral ligament:
- PP - distal sesamoid
- Impar ligament:
- DP - distal sesamoid
Navicular/podotrochlear bursa:
- Fluid filled pocket
- Located between sesamoid + DDFT
- Separated from DIP joint by impar ligament
- Protects deep Digital flexor tendon (DDFT)
124
Lateral/ungual cartilages (equine)
- Cartilage plates
- Palmar processes DP
- Medial + lateral
- Project above level of hoof
- Shock absorption
- Palpable feature in liver animal (proximal part)
Radiography:
- Cartilage not visible
- Mineralise as age
- "sidebone"
125
Extensor tendons (equine)
Below carpus = fibrous tissue only
(tendons/ligaments)
Muscle bellies in antebrachium
Common digital extensor (CDE):
- Crosses dorsal aspect carpus
- Joined by 2 branches of suspensory ligament
- Insert PP, MP + DP
Latera digital extensor (LDE):
- Inserts PP
- Separates from CDE
126
Flexor tendons (equine)
Superficial digital flexor tendon:
- Accessory check ligament
- O = proximal to carpal canal
- Passes through carpal canal
- Splits to allow DDFT pass through it
- Inserts MP
Deep digital flexor tendon:
- Passes through carpal canal
- Accessory check ligament
- Originates from fibrocartilage plate on palmar aspect of carpus
- Fuses with DDFT
- Passes through split in SDFT
- Runs over navicular bursa/navicular bone
- Inserts DP
127
Metacarpal region palpation (equine)
Dorsal aspect = extensor tendons
Palmar aspect =
- Skin
- SDFT
- DDFT
- Check ligament (fuses with DDFT)
- Suspensory ligament (splits into 2 branches)
Clinical relevance:
- Tendon trauma in common
- Ultrasound examination is ideal for soft tissue damage
128
Metacarpal region - ultrasound (equine)
Most lesions appear as hypoechoic (grey) from inflammation + necrosis; white lines are normal appearance of collagen
Utility severity = how much of tendon is involved
Convince owner and trainer to rest patient if lesions appear.
129
Digital region (equine)
Scutum = cartilage shield/plate
- Palmar aspect joints
- MCP = intersesamoidean ligament
- Smooth passage for tendons
Annular ligaments:
- Hold DDFT + SDFT against bones
Tendon sheath:
- Shared by SDFT + DDFT
- Extends from annular ligament distally
- Inflammation - increased pressure
Clinical considerations:
- Palpation of swellings
- Bony swellings: splints
- Soft swellings
- Articular joint
- Between suspensory ligament + MC3
- Tendon sheath
- Palmar to suspensory ligament + proximal to annular ligament
130
Stay apparatus
Most of weight borne on forelimb
Mechanism for passive weight bearing
Serratus ventralis
- Suspends weight of body between forelimbs
Maintenance of extension:
- Shoulder:
- Biceps brachii
- Elbow:
- Collateral ligaments
- Alignment of bones
- Carpus:
- Lacertus fibrosis
Prevention of hyperextension of the:
- Carpus:
- Palmar fibrocartilage joint reinforcement
- SDFT and check ligament
- Retinaculum
- MCP joint:
- Suspensory ligament
- Common digital extensor
- Proximal sesamoids
- Distal sesamoidean ligaments
- MCP, PIP + DIP joints:
- Prevention of hyperextension = DDFT + SDFT - check ligaments
- Annular ligaments
- Bind them to palmar aspect of digit
131
Blood supply (equine)
Arterial supply similar to dog
Brachial artery
- Medial aspect elbow
- Palpable pulse
Medial + lateral digital arteries
- Abaxial aspects proximal sesamoids (behind fetlock joint)
- Palpable pulse
Venous drainage
- Similar to dog
- No clinical relevance
132
Nerve supply (equine)
Brachial plexus:
- Same branches as dog
- Same motor function as dog
Nerve damage uncommon
Suprascapular nerve (motor)
- Runs round neck of scapula
- Supplies:
- Supraspinatous
- Infraspinatous
- No cutaneous sensation
- Damage causes joint instability
Different sensory areas:
- Distal to carpus
- Median + ulna nerves combine
- Supply pastern + foot
- Combined with musculocutanous nerve
- Medial aspect metacarpal area
133
Median + ulnar nerves (equine)
Combine distal to carpus
2 major branches:
1) Palmar metacarpal nerves
- Paired (medial + lateral)
- Run between MC3 + splint bones
- Emerge at distal end of splint bones
- Supply dorsal aspect of digit
2) Palmar nerves
- Paired (medial + lateral)
- Between suspensory ligament + SDFT
- Cross abaxial aspect proximal sesamoids
Become:
- Palmar digital nerve
- Dorsal and palmar branches
- Supplies hoof contents
134
Hoof
Divided into 4 parts
- Wall (toe/quarters/heel/bar)
- Periople
- Sole
- Frog
135
Solar surface of hoof
Frog - rubbery wedge shaped structure between the bars
Bars of heel - 2 bars on each hoof, on either side of frog
Sole - covers the bottom of foot
White line - interconnected lamina
Walls - weight bearing (nails)
Bulbs of heel
Central sulcus
Collateral sulci
Coronary band:
- Transition between skin + hoof wall
- Produces hoof wall
- Marks boundary between skin + hoof
Periople:
- Round coronary region
- Produces waterproof later
- Extends 2/3 way down hoof
- Prevents evaporation, wear + tear
136
Hoof contents
- Middle phalanx (distal end/P2)
- Distal phalanx (P3)
- DIP joint
- Navicular bone
- DDFT
- Navicular bursa
Clinical significance:
- Penetration injuries:
- Significance depends on:
- Location
- Depth
- Abscess formation/pododermatitis
- Significant pain
- Palpable digital pulses
Lateral/ungual cartilages:
- Cartilage plates
- Palmar processes DP
- Medial (inner) + lateral (outer)
- Shock absorption
- Mineralise as age (sidebone)
137
Hoof production
Dermis (corium)
- Covers DP + digital cushion
- Blood + nerve supply
- Sensitive
- Supplies germinative layer
Germinative layer:
- Produces epidermis
- Active in 2 areas only
- Coronary band
- Solar suface
Dermis fused to DP
- Surface of dermis forms vertical ridges = laminae
- Primary = macroscopic
- Secondary = microscopic
- Secondary (contains blood + nerves)
Hoof wall:
- Epidermal horn tubes glide distally
- Internal surface interdigitates with dermal laminae
- Forms corresponding primary + secondary laminae known as epidermal/insensitive laminae
Interdigitation = white line
- Prevents separation of epidermis from DP
- Transfers weight from hoof wall to DP
Solar surface - active germinative layer
- Sole:
- Keratinised flakes
- No tubular horns
- Frog:
- Incomplete keratinisation
- Soft + elastic
138
Coronary band
Dermis formed into conical shaped papillae
Produce epidermis in the form of tubes of keratin
Extend distally towards ground
Grow 5-6mm / 1/4 inch per month
Gaps filled by intertubular horn
Form hoof wall
Weight bearing surface
139
Weight bearing in hooves
Frog contacts ground first
Forces passed to:
- Digital cushion (blood forced back up leg)
- Lateral cartilages
Hoof wall contacts ground
- Weight transferred to distal phalanx then via laminae to hoof wall
140
Farrier
Foot trimming
- Horn grows continuously
Shoeing:
- Protect weight bearing wall
- Shape doesn't restrict heel
- Therapeutic shoes
Nails:
- Insensitive laminae
- Outwith white line
- Sledge tipped nails
- Tips clipped + flattened = clenches
- Must raise clenches before one can remove shoe
141
Ruminant hoof
- Cloven hoof
- Medial + lateral claws
- Interdigital cleft
- Sole
- Heel
- No frog
- No angles and the bars
- Wall
- Lateral - convex
- Continuous with heel
- Medial - vertical
- Stops at paralegal groove
- Transition hard - soft horn
- Prone to damage
Shock absorption:
- Bulbous heels
- Digital cushion
- Digits splay
- Supported by interdigital ligaments
- No lateral cartilages
- No frog
142
Ruminant hoof growth
- Coronary band
- Only part of dermis covered by laminae
- Sensitive laminae
- Insensitive laminae
- Primary only
- No secondary
143
Sheep + goat hooves
Goat hooves are well adapted for climbing hard walls, softer soles for traction on steep inclines
Same as cattle
Skin gland proximal to inter-digital cleft
- Waxy substance produced by sebaceous + serous gland
- Also seen in ungulates
Overgrowth a problem
- Need to be trimmed
144
Pig hoof
- Similar to ruminants
- No frog
- No lateral cartilages
145
Comparative anatomy of scapula
Dog:
- Acromion process
- Tuber spine is absent
- Supraglenoid tubercle part of glenoid cavity
Horse:
- Narrow supraspinous fossa
- Acromion process is absent
- Prominent tuber spine
- Supraglenoid tubercle separate from glenoid cavity
- Glenoid notch is present
Cow:
- Broad dorsal border + larger infraspinous fossa
- Acromion process is blunt + doesn't reach to the level of glenoid cavity
- Tuber spine is less prominent/absent
- Indistinct glenoid notch
Pig:
- Round cranial margin
- Poorly defined acromion
- Prominent tuber
146
Comparative anatomy of the humerus
Horse:
- Greater tubercle
- Cranial + caudal parts
- Level with humeral head
- Lesser tubercle
- Similar size
- Intermediate tubercle
- Double intertubercular groove
- Supratrochlear foramen absent
- Very prominent deltoid tuberosity
Dog:
- Single greater tubercle
- Supratrochlear foramen
Cow:
1) greater tubercle
- Cranial + caudal parts
- Much higher level than humeral head
- Pointed shape
- Cranial part of greater tubercle is massive and overhangs inter tubercular groove medially
2) Single inter tubercular groove
3) Circular area for insertion of infraspinatus m.
- Lateral aspect of greater tubercle
4) Relatively to horse deltoid tuberosity is small
5) No supratrochlear foramen
Pig:
- Greater tubercle
- Cranial + caudal parts
- Also higher than humeral head
- Rounded shape
- Almost enclose inter tubercular groove
- Single interbucular groove
- No supratrochlear foramen
- No flattened thumb print
147
Comparative anatomy of radius + ulna
Dog + cat:
- 2 separate complete bones
- Rotation possible
Horse:
- Proximal ulna present + fused to radius
- Body of ulna absent
- Distal ulna present + fused with radius
- Lateral styloid process
- Radius - medial styloid process
- No rotation possible
Ruminant:
- 2 complete bones
- Fuse as animal ages
- No rotation
Pig:
- 2 complete separate bones
- Ulna same diameter as radius
- No interosseous space
- No rotation
148
Comparative anatomy of carpus
Dog + cat:
- Radial + intermediate fused
- Distal row all present
Horse:
- All present (except variable 1st CB)
Pig:
- All present
Ruminant:
- Proximal row all present
- Distal row:
- 1st CB absent
- 2nd + 3rd CB fused
149
Comparative anatomy of carpal canal
Dog + cat:
- Only DDFT passes through
Horse:
- Both DDFT + SDFT
Ruminant + pig
- DDFT + half SDFT (SDFT splits)
150
Comparative anatomy of the manus
Dog:
- Digitigrade
- Weight bears on digit 3rd phalanges)
- 2nd-5th weight bearing
- 1st digit vestigial
Horse:
- Unguligrade
- Perissodactlya
- Weightbears on distal phalanx
- 3rd MC and digit only
- Rest absent
Ruminants:
- Unguligrade
- Artiodactyla
- 3rd + 4th digits are present
- Weight bears on distal phalanx
151
Comparative anatomy of metacarpal bones
Ruminants:
- MC1 + 2 absent
- MC 3 + 4:
- Separate in foetal life
- Fuses in uterus
- 2 medullary cavities
- Axial bony septum
- Proximal end - 1 articular surface
- Distal end - 2 articular sufaces
- 4 Centres of ossification
- MC 5 - vestigial spur
152
