Axial Skeleton Flashcards
How is the musculoskeletal system assessed in a clinical examination?
- Observation – lame? Cause of lameness? Describe it?
- Palpation – pain, heat or swelling? Where? Muscle wastage? Group of muscles? Why? Consequence of this?
- Manipulation – range in motion, what joint is affected? What part of the joint? Why?
- Mechanical tests and clinical imaging – cranial drawer test, tibial thrust test and ortolani test. Radiography, ultrasonography, MRI and CT.
What are some examples of active muscle control?
Muscles to maintain body posture = antigravity extensor muscles of the limbs and spine.
To move limb joints = flexor and extensor muscles
To move jaw = muscles of mastication/trigeminal muscles
Shape the lips = muscles of facial expression
Move food into GI tract = palatine and pharyngeal muscles
Support abdominal organs = abdominal muscles
What is biomechanics?
The study of the mechanical laws relating to the movement or structure of living organisms. Forces loads and levers. Application of basic biomechanical principles is fundamental to understanding the function of the locomotor system.
Describe the function of levers in biomechanics.
Muscles can only deliver so much force and levers can change the force required to move a set mass, or can increase the speed of movement for a given force, they do this by altering the lengths of the lever arms.
Describe the function of muscle distribution in biomechanics.
More muscle mass is found proximally, as proximal muscles tend to be larger, better adapted to more powerful movements and have longer fascicles. Distal muscles tend to be smaller and better adapted to develop force and have shorter fascicles and longer tendons, which store elastic energy or pulling on distal structure to help decrease mass in the distal limb.
Describe the function of tendons in biomechanics.
Tendons that act as strings tend to be thinner relative to length and tendons that act as springs tend to be thicker relative to length. Spring tendons have greater elastic components and for them to act like springs the attached muscle fibres need to develop force so that the tendon can be stretched. Reduced muscle fibre content reduces this need for energy.
Describe the 2 ends of a muscle attachment.
Origin - typically proximal and generally moves less
Insertion - typically distal and generally moves more
Define translation.
Moving 2 structures relative to one another across a plane.
Define varus and valgus.
Varus – 2 distal structures are more medially placed than a more proximal structure.
Valgus – 2 distal structures are more laterally placed than a more proximal structure.
Define luxation and subluxation.
Luxation or subluxation describe versions of dislocations. Subluxation means a smaller dislocation.
Define avulsion.
Avulsion fractures are when a piece of bone has broken away from a larger bone structure. Happens when a muscle and a tendon have pulled on that piece of bone on that insertion point.
Define transection.
Describes how you would cut across bone or muscle in surgery or dissection
What are the 4 functions of the vertebral column?
- Provide support to body weight
- Allow force transfer
- Be flexible to allow movement
- Protect the spinal cord and nerves
What is the structure of intervertebral discs?
- Round discs of tissue that sit between the bodies of the vertebrae
- Has an annulus fibrosis tough ring and a nucleus pulposus soft centre. Annulus is thinner dorsally
- Fibrocartilaginous
What is the function of intervertebral discs?
Provides most stability of all support structures by resisting compression and absorbing shock.
Most common cause of spinal problems in dogs.
What are articular facet joints and their function?
Articular facet joints in between individual bones. They are synovial joints that can get osteoarthritis and cause chord/spinal compression.
What are flaval ligaments and their function?
Flaval ligaments are yellow and sit between facet joints. They are very elastic and help return the vertebral column to the neutral position after flexion.
What are supraspinous ligaments and their function?
Run all the way along. They resist hyper flexion of the vertebral column and run lumber to thoracic and continues as the nuchal ligament.
What are dorsal longitudinal ligaments and their function?
Dorsal longitudinal ligaments are dorsal to the bodies of the vertebrae and resist hyper flexion.
What are ventral longitudinal ligaments and their function?
Ventral longitudinal ligaments are ventral to the bodies of the vertebrae and resist hyper extension.
What is intervertebral disc extrusion?
Intercalated discs have annulus fibrosis that is thinner dorsally than ventrally so if the nucleus pulposus becomes herniated out of the intervertebral disc, it will likely escape dorsally and put pressure on the spinal cord in an intervertebral disc extrusion. This could have effects on the signals running to and from the brain.
What are intercapital ligaments and their function?
Links the heads of rib pairs ventral to the spinal cord and dorsal to the intervertebral discs (tether rib pairs together dorsally).
Their presence from T2-10 makes discs extrusion uncommon in this region.
Describe epaxial musculature and their function.
- Musculature on the dorsal aspect of the transverse processes
- Extension of the spine or lateral movement if engaged on one side
- Dorsal branches of spinal nerves
- 3 parallel columns
Describe the hypaxial musculature and their function.
- Ventral to the transverse processes
- Flexion of the spine
- Ventral branches of spinal nerves
- Includes thoracic and abdominal wall musculature
- Also called sublumbar muscles in lumbar region
