general principles, bones and joints of back and neck Flashcards
static models of back and neck bending in vertical plane
not a good representation
string and bow model
- the bow:
- vertebrae and intervertebral discs,
- supported by ligaments and muscles; supraspinous lig, epaxial mm, hypaxial mm
- compressionally strong but w some flexibility
- the string
- muscles w variable tension braces by rib cage
- cranial; scalenus m
- caudal; abdominal mm
- tightening –> flex the box
string and bow model is
- delicately balanced
- dynamic; can respond to changes
- maturity brings stronger mm; less sagging of the belly and back
locomotion; ____ w ground is essential
friction
locomotion; propulsive force acr around pivot near
thoraco-lumbar junction
from a flexed back position
- Hindlimb; which is on the ground, is going to be retracted and extended (propulsion)
- Forelimb is going to be protracted (recovery)
- Back is going to be extended
- Uses axial mm and extrinsic mm
Extensors of back
epaxial mm
Extensors of hip
gluteals, hamstrings
Extensors of stifle
quadriceps
Extensors of hock
gastrocnemius
Protractor forelimb
brachiocephalic
Extensors of shoulder
supraspinatus
From an extended back position
- Forelimb is now on the ground, is going to be retracted and extended
- Hind limb is going to be protracted (recovery)
- Back is going to be flexed
Flexors of back
hypaxials, abdominal mm
Retractors of forelimb
latissimus dorsi, deep pecs
Extensors of elbow
triceps
Flexors of hip
iliopsoas, rectus femoris
scaling of head and neck
- As body size increases
- Suppose body increases in size by factor of x
- Length increases by a factor of x
- Muscle strength (area) by x^2
- Weight (volume) increases by x^3
- Moment (leverage) increases by x^4
In large animals the increase in epaxial mm alone is insufficient
- Large animals have difficulty raising their heads (esp grazers)
- They develop elastic fibers in nuchal ligament; stores energy
- And large spinous processes (withers)
bending in a horizontal plane
- Sudden changes in direction
- Dog wagging its tail
- V limited in horse
- Partly fused articular and transverse processes of lumbar vertebra
- Sheep and cattle intermediate
- Pig has a lot lateral movement
Rotation
- Twisting of back when jumping over an obstacle
- Rolling of back in a pacing horse
Cervical vertebrae
- Small spinous process
- Large articular area
- Some DV and lateral movement
Atlanto-occipital joint
- nodding
- Most DV movement of head and neck
- Little lateral or rotational movement
Antlanto-axial joint
- head shaking joint
- Little DV movement
- Rotation permitted
- Some lateral movement
Thoracic vertebrae
- Tall spinous processes; tallest differs dog and horse
- Dog T 11; anticlinal; most bending here in dogs ( stands right up, ones before point backwards, ones behind point forwards)
- Site of many problems especially in small dogs with long backs
- Articulate with ribs
Lumbar vertebrae
- Large transverse processes
- Horse; Transverse processes of L4-5-6 articulate with each other and L6 articulates with sacrum
- Very stable
Sacrum
- Completely fused dog and horse
- Dog; 3 small partly fused spines
- Horse; 5 separate spines
Caudal vertebrae
Spinous and transverse processes disappear caudally
Intervertebral discs
- Fibrocartilaginous joint
- Annulus fibrosis thicker ventrally
- ~16% of vertebral length in dogs and ~10% in ungulates (25% in humans)
Joints of articular processes
- Synovial joints between facets on vertebral arches
- Cervical and cranial thoracic vertebrae
- Flat & large, loose joint capsule
- Movement comparatively free
- Caudal thoracic and lumbar vertebrae
- Flat , becoming concave/convex
- Movement much reduced and restricted to median plane (ie flexion and extension)
Ligaments of the vertebral column
- Ventral longitudinal ligament
- Dorsal longitudinal ligament
- Supraspinous ligament
Ventral longitudinal ligament
- Thorax to sacrum
- Wider and stronger in lumbar region
Dorsal longitudinal ligament
- Floor of vertebral cranial
- Axis to sacrum
- Wider over intervertebral disc but weaker than VLL
Supraspinous ligament
- Dorsal to spinous processes
- From occipital bone or axis to sacrum
- Modified in neck into the NUCHAL ligament
- Merges with tendons of epaxial muscles T & L areas
Nuchal ligament in dog
- Goes from spine of axis to spinous process of T1
- Paired fibrous band with yellow elastic fibers
Nuchal ligament in horse
- 2 parts (both paired)
- Funicular and lamellar
- funicular is dorsal part
- lamellar is big triangle
- From occipital bone and cervical vertebrae to spinous processes of first few T vertebra
- Continues caudally as non elastic supraspinous ligament
nuchal ligament; horse,
funicular part
- Most dorsal part
- Paired (left and right)
- Flattened cranially becoming cord like in neck to flattened strap over thoracic spines
- Gradual change from elastic to fibrous
nuchal ligament; horse,
lamellar part
- Paired
- Lamellae (sheets) of elastic tissue
- Digitations from spinous processes T2-3 to C2-6
- 1st lamella to axis is very strong, becoming weaker caudally
- Present in ox, weak in pig, absent in dog
bursa in nuchal ligament
- function; minimize pressure over bony prominence
- atlantal bursa; over atlas under flat funicular part
- supraspinous bursa; over spinous processes T2-3
Seat of Poll evil
disease thats infection of atlantal bursa
Seat of fistulous withers
disease thats infection of supraspinous bursa
Atlanto-occipital joint
capsule and movement
- Occipital condyles → “ cavities” of the atlas
- Joint capsule; 1 for each condyle but join ventrally
- Movement mainly flexion and extension
Ligaments of atlanto-occipital joint
- dorsal A-O membrane
- Ventral A-O membrane
- 2 lateral ligaments; comparatively weak
atlanto axial joint type
pivot
dens of axis sits on
floor of atlas (goes inside vertebral foramen of atlas)
Atlanto axial joint capsule
loose; ample laterally
Atlanto axial joint movement
mainly rotation
ligaments of atlanto-axial joint
- Dorsal A-A membrane
- Ventral A-A membrane
- Interspinous
Ligaments of dens: (atlanto-axial joint)
- Dogs: 3 parts
- Apical (middle part) and 2 alar (2 lateral parts)
- Pass through to foramen magnum and occipital condyles
- Horse; 1 part
- To floor of atlas only
Transverse atlantal ligament (atlanto axial joint)
- strap across dens from floor of atlas
- Holds dens firmly on floor of atlas (not actually attached to dens)
- If ruptured, dens pushes into spinal cord → death (what happens when you hang people)
