Changes

'''What this machine is made of: passive and active tissues'''  

'''What this machine is made of: passive and active tissues'''  

 

The tissues of the musculoskeletal system are bone, cartilage, ligament, tendon, fascia and muscle (Fig. 2.1).

The tissues of the musculoskeletal system are bone, cartilage, ligament, tendon, fascia and muscle (Fig. 2.1).

The non-muscular parts support the body passively by resisting forces that are applied to the body from outside (extrinsic) or those that are created intrinsically within the body.  The most significant extrinsic forces are the earth's gravitational force on the mass of the animal, and the reaction of the ground.  An animal, once it is born, must spend most of its life battling with gravity and the problems of contact with ground surfaces.  

The non-muscular parts support the body passively by resisting forces that are applied to the body from outside (extrinsic) or those that are created intrinsically within the body.  The most significant extrinsic forces are the earth's gravitational force on the mass of the animal, and the reaction of the ground.  An animal, once it is born, must spend most of its life battling with gravity and the problems of contact with ground surfaces.  

Animals also derive support from the activity of their muscles, as evidenced from the inability of an anesthetised animal to stand. This active type of support will be discussed in Sections 4 and 5.  

Animals also derive support from the activity of their muscles, as evidenced from the inability of an anesthetised animal to stand. This active type of support will be discussed in Sections 4 and 5.  

 

::2.1 Tissues of the musculoskeletal system.  

 

::This is a stylised view of the lateral aspect of the proximal left forelimb of the sheep.  The skeleton is made of bones and cartilages.  A combination of ligaments, muscles & tendons, and sheets of fascia, examples of which are shown, hold these together. Without these soft tissues around them, the jointed bones will not support the weight of the sheep.  

[[File:Fig 2.1.png|thumb|'''2.1''' Tissues of the musculoskeletal system.

This is a stylised view of the lateral aspect of the proximal left forelimb of the sheep.  The skeleton is made of bones and cartilages.  A combination of ligaments, muscles & tendons, and sheets of fascia, examples of which are shown, hold these together. Without these soft tissues around them, the jointed bones will not support the weight of the sheep.]]

'''The elasticity of tissues'''

'''The elasticity of tissues'''

   

   

Elasticity is measured by determining the effect of stress, defined as force per unit area, on the shape of the material.  When this stress acts in only one direction, this shape change is measured as strain, the distortion per original unit distance, expressed as a percentage.  

Elasticity is measured by determining the effect of stress, defined as force per unit area, on the shape of the material.  When this stress acts in only one direction, this shape change is measured as strain, the distortion per original unit distance, expressed as a percentage.  

At a particular percentage of strain, ''p'', a stiffer material will store more elastic energy than a more elastic tissue.  Suppose that at this strain percentage, the material can no longer be deformed without damage.  Fracture will occur, and because the stiffer material releases more energy it will shatter rather that suffering a simple break.  Bone fractures are discussed later in Chapter 3.  

At a particular percentage of strain, ρ, a stiffer material will store more elastic energy than a more elastic tissue.  Suppose that at this strain percentage, the material can no longer be deformed without damage.  Fracture will occur, and because the stiffer material releases more energy it will shatter rather that suffering a simple break.  Bone fractures are discussed later in Chapter 3.