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Quadrupedal Mechanics - Anatomy & Physiology (view source)
Revision as of 11:15, 24 February 2013
, 11:15, 24 February 2013no edit summary
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).
[[File:Fig 2.1.png|thumb|2.1 Tissues of the musculoskeletal system.
[[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.]]
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.]]
'''Stress, strain & elasticity'''
An appreciation of the concept of elasticity is essential to understanding the mechanics of animals.
All materials are elastic to a lesser or a greater extent, even tissues like bone that seem to be stiff rather than elastic. The stiffness is only relative. After being deformed by an external force, all tissues must return to their original shape. If they did not, the body would be permanently deformed.
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, r, 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.
[[File:Fig 2.2.png|thumb|'''2.2''' Two linearly elastic tissues A and B have stress - strain curves as shown. The energy absorbed by A and B is represented here by the area beneath the curve, At any given value of stress, a, the strain r is less for A than for B. A has absorbed less energy than B. A is stiffer than B. If A and B were bones, A would be the more mineralised.]]