VT111 Lec. 7 Appendicular Skeleton

Appendicular Skeleton

Thoracic limb:

• Scapula

• Humerus

• Ulna

• Radius

• Carpal bones

• Metacarpal bones

• Phalanges

Pelvic limb:

• Pelvis

• Femur

• Patella

• Fabellae

• Tibia

• Fibula

• Tarsal bones
  Metatarsal bones

• Phalanges

Thoracic Limb

• No direct bony connection with axial skeleton

• No clavicle to join the scapula with sternum

  • (Incomplete) Pectoral girdle

    • Common only in primates also rabbits; not in dogs or cats

Scapula

• Flat and triangular

• Lateral surface

  • Spine

    • Distal end: acromion

• Distal end

  • Glenoid cavity

  • Coracoid process

Humerus

• Proximal:

  • Head → scapula

  • Tubercles: greater and lesser

• Middle:

  • Shaft (diaphysis)

• Distal:

  • Condyle

    • Trochlea (medial) àulna

    • Capitulum (lateral) à radius

  • Epicondyles: medial and lateral

  • Supratrochlear foramen

    • Unique to dog and cat

  • Olecranon fossa

Ulna

• In dogs/cats, starts medially and ends laterally

• Olecranon process

  • Point of elbow

  • Attachment site of tendon of triceps brachii

• Trochlear notch

  • Anconeal process

    • Fits into olecranon fossa during extension

  • Coronoid processes: medial and lateral

• Styloid process (distal): lateral

• Horse and cow

  • Ulna partially fused to radius (incomplete)

Radius

• Main weight bearing bone

• Head

• Radial tuberosity

  • Medial

• Styloid process: medial

Carpal Bones

• Carpus = wrist

  • Horse = knee

  • Variety among species

    • Humans and pigs have 8 bones

• 2 rows of bones

  • Proximal

    • Radial carpal bone: medial

    • Ulnar carpal bone: lateral

    • Accessory carpal bone: lateral

• Distal

  • Numbered, starting at medial side

    • (I – IV)

Metacarpals

• Numbered from medial (MC I = dewclaw) to lateral (MC V)

• Horse: one toed

  • Only one metacarpal is weight bearing

    • MC III = canon bone

    • Bracketed by vestigial metacarpal bones MC II and MC IV (splint bone; incomplete)

• Cattle: two toed

  • Weight bearing on fused MC III and MC IV

Phalanges

• Digits

  • Each composed of 2-3 bones (phalanges)

  • Proximal, middle, distal (P1, P2, P3)

    • Distal ends in ungual process (claw, nail)

  • Sesamoid bones (inside of tendons)

    • Location and number vary among species

• Horses – only 1 digit

  • Long pastern (P1) (proximal)

  • Short pastern (P2) (middle)

  • Coffin bone (P3) (distal)

    • Sesamoids:

      • proximal at fetlock joint

      • distal inside of coffin bone (navicular bone)

• Cattle: 4 digits

  •  3rd and 4th support body weight

    • 2nd and 5th vestigial = dewclaws

Thoracic Limb Bones of Cattle

• Two fused metacarpal bones 

  • Metacarpal III  

  • Metacarpal IV

• Four digits             

  • 2 weight-bearing      

  • 2 dewclaws

• Sesamoid bones             

  • 2 proximal                  

  • 1 distal

Equine Thoracic Limb Bones

• 1 digit with 3 phalanges

  • Long pastern bone (proximal phalanx)

  • Short pastern bone (middle phalanx)

  • Coffin bone (distal phalanx)

• 3 sesamoid bones

  • 2 proximal at the fetlock

  • 1 distal = navicular

Pelvic Limb

• Directly connected to axial skeleton via sacroiliac joint

  • Ilium of pelvis with sacrum of spinal column

• Consists of:

  • Pelvis

  • Femur

  • Patella

  • Tibia

  • Fibula

  • Tarsal bones

  • Phalanges

Pelvic Girdle

• Pelvis (os coxae) is actually 3 bones on each side that are fused

1. Ilium

• Wing

• Cattle/horse: processes

  • Medial: tuber sacrale – part of sacroiliac joint

  • Lateral: tuber coxae – point of hip

2. Ischium

• Caudal most part of pelvis

  • Ischial tuberosities = Sitz bones

3. Pubis

• Medial

• Obturator foramen

• 2 sides of pelvis joined with fibrocartilage

•      ventrally by pelvic symphysis

• Union between ilium and sacrum is a

•       fibrocartilaginous joint – sacroiliac joint

• 3 bones come together at acetabulum

  • Encloses head of femur to make coxofemoral (hip) joint

Horse Pelvis

• Tuber sacrale

  • Point of croup

• Tuber ischii

  • Point of buttock

    • cow: pin

• Tuber coxae

  • Point of hip

    • cow: hook

Cattle Pelvis

Femur

• Head of femur

  • Ball of ball-and-socket coxofemoral (hip) joint

  • Attached to shaft by neck

  • Greater and lesser trochanter

  • Trochlea (patellar groove)

    • Surface which patella glides against

  • Medial and lateral condyles

  • Medial and lateral epicondyles

  • Fovea capitis

    • pit in head of femur where ligamentum teres (round ligament) inserts

Patella and Fabellae 

• Sesamoid Bones

• Largest sesamoid:

  • Patella

    • In distal tendon of quadriceps femoris muscle

    • Helps to protect tendon

• Fabellae (“little beans”)

  • Caudal to joint: 2 in proximal gastrocnemius (calf muscle) muscle tendons behind femoral condyles (lateral > medial)

  • Caudal to joint: 1 in tendon of popliteus (near lateral condyle of tibia)

  • Present in dogs and cats

  • 10-30% humans

  • Not present in cattle or horses

Tibia

• Main weight bearing bone of lower leg

• Stifle joint - tibia - hock joint

• Condyles

• Intercondylar eminence

• Tibial tuberosity

  • Attachment for patellar ligament

• Tibial ridge/(anterior)crest

• Medial malleolus

  • Medial ankle “knob”

Fibula

• Lateral structure

• Proximal extremity

  • Fibular head

• Shaft

• Distal extremity

  • Lateral malleolus

    • Lateral “knob” of ankle

• Shaft not present in horse and cattle

Tarsal Bones

• Tarsus – dog 7 bones

  • Human = ankle

  • Domestic animals = hock

  • Proximal row (3 bones)

    • Tibial tarsal bone - medial

      • Large trochlea articulates with tibia

    • Fibular tarsal bone - lateral

      • Calcaneal tuberosity (human heel)

        • Attachment for tendon of gastrocnemius muscle

      • Central tarsal bone

  • Distal row

    • Numbered medial to lateral

      • (I – IV)

The Horse

Labeled Horse

The Horse: Carpus

The Horse: Tarsus

Phalanges

• Similar to forelimb

  • Dogs/cats usually only have 4

    • Digits II, III, IV, V

The Horse

Equine Terminology

Forelimb:

• Knee: carpus

• Fetlock: metacarpal-phalangeal joint

• Pastern: the part of the foot extending from the fetlock to the top of the hoof

  • Pastern joint: P1-P2

  • Coffin joint: P2-P3

Hindlimb:

• Stifle: the femoral-tibial joint (aka your knee)

• Hock: the tarsus

• Fetlock: metatarsal-phalangeal joint

• Pastern: the part of the foot extending from the fetlock to the top of the hoof

  • Pastern joint: P1-P2

  • Coffin joint: P2-P3

Equine Hock Joint

Horse Hindlimb

Visceral Skeleton (random bones)

• Bones that form in soft organs

  • Os cordis

    • Ruminants

      • Supports valves of heart

  • Os penis

    • In penis of dog, beaver, walrus, chimps

  • Os rostri

    • Swine

      • Strengthens the snout: rooting

Hinge Joint

• Pulley shaped connection fits into concave space

• Works exactly like a hinge

  • Flexion/extension

• Ex: elbow

Gliding/Plane Joint

• Flat articular surfaces

• Sliding movements

• Range of motion is limited in these joints and does not involve rotation

• Ex: carpal bones

Pivot Joint

• Rounded end of one bone fits into a “sleeve” of either bone or ligament

• Rotation movement

• Ex: atlantoaxial joint

Ball and Socket Joint

• Spherical head of one bone fits into cup of another.

• Movement in many planes

  • Greatest range of motion, as all movement types are possible in all directions

  • Extreme freedom of movement

• Ex: coxofemoral joint; scapulohumeral joint

Condyloid Joint

• Also called ellipsoidal joint

• Oval surface fits into depression (fossa) of another bone

• Allows angular movement along two axes

• Ex: metocarpophalangeal joint

Saddle Joint

• Both ends have concave and convex surfaces for increased freedom of movement

• Saddle joints allow angular movements similar to condyloid joints but with a greater range of motion

• Ex: carpometacarpal joint (thumb)