SAQMG2

No. When standing and gently twisting from side to side motion also occurs in the lower limbs. Do the same again but this time sitting down. This should giveyou a better estimate of the range of rotation in your lumbar and thoracic spine.

The loading on the spine increases as the moment arm of the upper body weight increases.

Tendons connect muscles to bone.

Tendons and ligaments must withstand very high tensile forces.

Tendon and ligament cells are called fibroblasts.

Collagen accounts for at least 75% of the dry weight.

Collagen fibres are arranged completely in parallel in tendons whilst in ligaments they are partially branched and interwoven.

The ground substance functions to stabilise the collagenous structure and provides lubrication and spacing for the sliding of collagen fibrils.

In tendons, the loose connective tissue that binds together the bundles of collagen fibres is called paratenon.

Fibrocartilage is present at bone insertion sites.

The three regions of a typical tensile stress-strain curve for tendons and ligaments are the toe region, linear region, and failure region.

Ligaments have a greater ultimate tensile strain than tendons.

Strain rate sensitivity is the sensitivity of mechanical properties to the rate of application of strain.

The maximum levels of normal physiological stress and strain will be up to around 27 MPa and 3% in tendons, and 33 MPa and 5% to 15% in ligaments.

The anterior cruciate can be elongated by approximately 7 mm before rupturing completely.

Bone tissue is more strain rate sensitive than tendon or ligament tissue.

The stress in the contracted ligament is 11 times greater than that in the normal ligament when both are elongated to 20.5 mm. From diagram, 33 mm divided by 3 mm equals 11.

After a period of immobilisation, the ligament tissue recovers quicker thanits insertion sites.

The diameter of collagen fibres increases with maturation.

The collagen content of tendons and ligaments decreases with ageing.

Bone cells are called osteocytes.

The inorganic component, which consists mainly of crystals of calciumphosphate, gives bone its characteristic hardness and rigidity.

Compact bone tissue contains haversian canals. These contain blood vesselswhich are needed to supply the bone tissue with nutrients.

When a material is under a tensile load it will elongate.

Strain is defined as the change in length divided by the original length.

The SI units of stress are newtons per metre squared (N m-2).

The Young's modulus for diamond is 120,000 times greater than that ofrubber (from 1200/0.01).

Using the definition for Young's modulus:Young's modulus =stress/strainInserting the values calculated in the Worked Example in Section 2.2:Young's modulus = 90/0.005= 18000 MNm-2 = 18 GNm-2Thus, the Young's modulus for the cortical bone sample is 18 GNm-2.

Cortical bone is stiffer than wood (it has a larger Young's modulus than wood) but more flexible than glass, aluminium and steel (it has a smaller Young's modulus than all of these).

The haversian systems are only weakly bound together by a cement-like ground substance (Section 1). This is the weakest part of cortical bone's microstructure so when it is loaded transversely, the haversian systems can be pulled apart comparatively weakly.

Cortical bone is less flexible in compression than cancellous bone as indicated by its larger Young's modulus.

Shear modulus is the ratio of shear stress to shear strain.

Cortical bone is stronger in tension than in shear.

Three point bending and cantilever bending are two types of bending loading.