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Importance knowing comparative anatomy
- lameness = production loss
- abbatoir= meat inspection
- look for growth plates
- horse vs cow
- sheep vs pig
- (horse vs pony)
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Scapula (Dog)
Dog: acromion process (no tuber), supraglenoid tubercle (SGT) is part of glenoid cavity
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Scapula (horse)
- horse: narrow supraspinous fossa, no acromion process
- small tuber top of spine
- SGT separate from glenoid cavity
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Scapula (cow)
- broad dorsal border
- acromion process
- small tuber along spine
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Scapula (pig)
- rounded cranial margin
- poorly defined acromion
- prominent tuber
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Humerus (dog)
- single greater tubercle
- supratrochlear foramen
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Humerous (horse)
- greater tubercle (cranial and caudal parts, level w/ humeral head)
- lesser tubercle (similar size)
- intermediate tubercle (double intertubercular groove)
- no supratrochlear foramen
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Humerus (cow)
- greater tubercle (cranial and caudal parts, much higher level than humeral head, pointed shape
- single intertubercular groove
- "flattened thumb print"
- no suprotrochlear foramen
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Humerus (pig)
- greater tubercle (cranial and caudal parts, higher than humeral head, rounded shape, almost encloses intertubercular groove)
- single intertubercular groove
- no supratrochlear foramen (like dog)
- no flattened thumb print (like cow)
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Radius and Ulna (cat/dog)
- 2 seperate complete bones
- rotation possible
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Radius and ulna (horse)
- proximal ulna present and fused to radius
- body of ulna absent
- distal ulna present and fused to radius (lateral styloid process)
- Radius: medial styloid process
- (no rotaion possible)
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Radius and ulna (ruminant)
- 2 complete bones
- fuse as animal ages
- no rotation
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Radius and ulna (pig)
- 2 complete separate bones
- ulna same diameter as radius
- no interosseous space
- no rotation
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Carpus (dog/cat)
- radial and intermediate fused
- distal row all present
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Carpus (horse)
- all present
- except variable 1st CB
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Carpus (ruminant)
- proximal row all present
- distal row: 1st CB absent
- 2nd and 3rd fused
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Carpal canal
- dog and cat: only DDFT passes through
- Horse: both DDFT & SDFT
- ruminant and pig: DDFT and HALF SDFT (b/c SDFT splits)
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Manus (dog)
- digitigrade
- weightbears on digit (3 phalanges)
- 2nd-5th weight bearing
- 1st digit vestigial
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Manus (horse)
- unguligrade (hoof)
- perissodactyla (uneven number)
- weightbears distal phalanx
- 3rd MC and digit only
- MC 2 and 4 vestigial
- all the rest are absent
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Manus (ruminants)
- Cattle, sheep, deer, goats, etc
- unguligrade (hoof)
- artyrodactyla (even number)
- weightbear on distal phalanx
- 3rd and 4th digits
- MC 3 & 4:
- separate in foetus
- fuse in uterus
- 2 medullary cavities
- axial boney septum
- proximal end- 1 articular surface
- distal end- 2 articular surfaces
- (4 centres of ossification)
- MC 1 and 2 absent
- MC 5 vestigial spur
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Digits (cow)
- digits 3 &4 weight bearingg
- 2 & 5 vestigial = dew claws (little hooves palmar aspect MCP joint
- Digit 1 absent
- joints: MCP joints x 2
- (2 x pairs proximal sesamoids, no dorsal sesamoid)
- PIP joint x 2
- DIP joint x 2
- 2 x distal sesamoid bones
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MCP joint support (ruminent)
- medial and lateral collateral ligaments (axial collateral ligaments- fused proximally)
- inter-sesamoidean ligaments (2 x proximal scuta)
- interdigital intersesamoidean ligament
- distal sesamoidean ligaments: (short, cruciate- no oblique and straight)
- interdigital phalaneal sesamoidean ligament
- axial aspect sesamoid- opposite PP
- helps hold PPs together
- suspensory ligament
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Digits (large ruminents)
large weight pushes digits apart, require strong attachments
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digits (small ruminents)
- less weight so less firmly attached
- accomodate tough ground
- proximal interdigital ligament (between PPs, no present in small ruminants)
- distal interdigital ligament ( between MPs, cross over, present in small and large)
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Manus- soft tissue structures
- similar arrangement to horse (2 brances)
- extensor tendons
- flexor tendons
- suspensory ligament (wraps around DDFT, fuses w/ SDFT, acts like check ligament of SDFT)
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Pig
- artyodactyla = even number
- bony elements for 4 digits
- 3rd and 4th weightbear
- 2 & 5th vestigial (don't hit the ground)
- Ligaments (too numerous to contemplate- remember basic principles)
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Clinical considerations
- forelimb lameness less common than hindlimb
- digital amputation possible
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Pelvis (wing of ilium)
- Dog/pig: vertical orientation, flat or convex cranial margin
- Horse/ruminants: horizontal orientation, concave cranial margin
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Pelvis (tuber ischium)
- cow: trifid (3 way projection)
- sheep: less distinct but still trifid
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Palpable featues of ruminant pelvis
- gluteal muscles are poorly developed
- hind limb retractor muscles (no extra head from lumbosacral fascia in cow)
- cows have an angular ump if not fat
- Tuber sacral (sacroiliac joint)
- tuber coxae
- tuber ischium
- ruminants= all palpabale
- (horses are variable)
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Sacroiliac joint
- Horse, cow and goat: 5 fused vertebrae
- cow: dorsal spinous process of sacrum fuse as ages
- horse: dorsal spnous processes are NOT fused/remain seperate
- pig/sheep:= 4 fused
- dog= 3 fused
- ** all species: articular surface ilium at S1 (fibrous joint-fused, minimal movement, except at parturation)
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Sacrotuberous ligament
- dog: fibrous band, S3 to tuber ischium
- cat: absent
- cow/horse: fibrous SHEET, sacrum to dorsal aspect ilium/ischium, forms lateral wall of pelvic cavity
- function: protection
- passage of nerves: greater ishiatic notch, lower ischiatic notch
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Parturition
- RELAXIN
- softens: pelvic ligaments, sacroiliac joint, broad ligament
- palpable changes
- pelvic inlet tips ventrally: increases aperture, improved angle
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obturator nerve
- passes through obturator forament
- short route to medial thigh (adductor muscles)
- damage at parturition:
- probelsm in COWS: oversized calves, stand up hind end first, "down cow"
- not a problem in HORSES: no oversized foals (uterus will control growth), stand up front end first
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Hip
- cow/horse/pig: same main features as dog, ligament of head of femur
- Horse: accessory ligament (from prepubic tendon)
- Cow: acetabulum has divided articular surface
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Femur
- sheep/pig/dog: trochlear ridges equal size
- cow: medial trochlear ridge larger than lateral, no tubercle, 3 patellar ligaments, no patellar locking mechanism, no fabellae or popliteal sesamoids
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Tibia and fibula
- pig: fibula complete and seperate from tibia
- ruminants: remnant of fibula proximally (fused, spur), separate remnant distally (doesn't fuse, joined to tibis by ligament)
- horse: proximal half of fibula fused to tibia, distal fragment also fused to tibia
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Tarsus
- Pig: same as dog (all sepeerate)
- cow: central and 4 fused, 2 & 3 fused, Talus (troclea straight, one at either end, rotation possible at proximal intertarsal joint= lateral 'cow' kick)
- Horse: 1 & 2 fused
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clinical significance
- Reciprocal apparatus: correcting breech calves/foals (must bend both joints)
- trauma
- spastic paresis: possibly inherited, contraction of gastrocnemius, section of tibial N/gastrocnemius attachments
- capped hock/bursitis
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Hoof Relevance
- horses: shoeing, corrective/therapeutic shoeing, lameness
- 90% equine lameness arises in the foot
- NO foot, NO horse!
- ruminants: welfare, production
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Horse Hoof external features
- walls- weight bearing
- sole- shouldn't contact ground
- white line- found between sole and wall
- angles of heel
- bars of heel
- bulbs of heel
- frog: anticoncussive, contral sulcus, collateral sulci
- Wall: weight bearing (toe, quarters, heel)
- coronary band: produces hoof wall, marks boundary between skin and hoof
- periople: round coronary region, produces waterproof layer ( extens 2/3 way down hoof, prevents evaportation)
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Horse hoof contents
- distal phalanx
- middle phalanx (distal end)
- DIP joint
- navicular bone
- DDFT
- Navicular burse
- digital cushion: deep to frog, elastic tissue, blood vessels, fat
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Functions of Digital cushion in Horse
- shock absorption
- protection: DDFT, distal phalanx, navicular burse, navicular bone
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Clinical significance of foot pad (horse)
- penetration injuries: significance depends on: location/depth
- abcess formation/pododermatitis/pus in the foot= significant pain, palpable digital pulses
- must dig!
- may need to apply poultice to soften horn
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Hoof contents (lateral/ungual cartilages)
- cartilage plates
- palmar processes DP
- medial and lateral
- shock absorption
- mineralize as age
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Hoof production (horse)
- dermis (corium): covers DP and digital cushion
- blood and nerve supply
- sensitive
- supplies germinative layer: produces epidermis, active in 2 areas only (coronary band and solar surface)
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Hoof production (coronary band)
- dermis formed into conical shaped papillae
- produce epidermis in 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
- weightbearing surface
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Hoof production (dermis/laminae)
- dermis fused to DP
- surface of dermis forms vertical ridges= laminae (primary/secondary=microscope)
- sensitive
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Hoof production (hoof wall)
- epidermal horn tubes glide distally
- internal surface intergitates with dermal laminae
- forms corresponding primary and secondary laminae (epidermal/insensitive laminae)
- (no nerve/blood supply)
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Hoof production (interdigitation/white line)
- interdigitation= white line
- prevents separation of epidermis from DP
- transfers weight from hoof wall to DP
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Hoof production (solar surface)
- = active germinative layer
- sole: keratinised flakes
- frog: incomplete keratinisation, soft/elastic
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weight bearing
- frog contacts ground first
- forces passes to: digital cushion (blood forced back up to leg), lateral cartilages
- hoof wall contacts ground: weight transfered to distal phalanx then via laminae to hoof wall
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Linical considerations (horse hoof)
- laminitis: numerous causes
- altered blood flow
- fluid accumulation between dermal and epidermal laminae
- significan pain
- DP rotation
- DP sinks
- slipper toe
- frog supports
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farrier (foot trimming/shoeing)
- foot trimming: horn grows continuously
- shoeing: protect weight bearing wall, shape doesn't restrict heel, therapeutic shoes (might restrict)
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farrier (nails)
- insensitive laminae
- outwith white line (sound)
- sledge tipped nails
- tips clipped and flattened= clenches
- must "raise clenches' before can remove shoe!
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Hoof shape (horse)
- front (weightbearing): broad rounded 1 toe clip
- back (propusion): narrow, pointed, 2 toe clips
- medial wall: more upright, straighter, usually 3 nails
- lateral wall: more angled, rounded, usually 4 nails
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Ruminant hoofs
- cloven hoof
- medial and lateral claws
- interdigital cleft
- sole, heel (no frog)
- wall: lateral (concave)- cont. with heel
- medial (vertical)- stops at parapedal groove, transition hard-soft horn, prone to damage
- white line
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ruminant hoof growth
- coronary band
- only part of dermis covered by laminae
- sensitive laminae
- insensitive laminae
- primary only
- no secondary
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Ruminant hoof external features
- shock absorption:
- bulbous heels
- digital cushion (deep)
- digits splay: supported by interdigital ligaments
- no lateral cartilages
- no frog
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Clinical considerations (ruminant hoof)
- horn overgrowth:
- soft ground
- FL= inner claw
- HL=outer claw
- solar ulcers: especially parapedal groove, secondary infections (can track up DDFT sheath)
- interdigital dermatitis
- white line disease
- laminitis
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Sheep
- same as cattle
- skin gland proximal to interdigital cleft
- overgrowth a problem- need pared
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pig feet
- similar to ruminants
- no frog
- no lateral cartilages
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