Idrætskader – 2011 – MiniModule 3/worksheet 1
Uwe Kersting
Review Questions MiniModule 3:
1. What are the two mechanical functions of bones?
Protection of organs --- Support and leverage
2. Most tissues and biological structures adapt to mechanical loading/usage. One of
them has very limited adaptational capacities at best. This is:
joint cartilage or hyaline cartilage
3. In which tissue do we find osteocytes (a) and where do we find chondrocytes (b)?
(a) bone tissue
(b) cartilage tissue
4. How does bone tissue grow? Explain two types of ossification.
Bone development and growth
Bone formation/development always happens in
Ossification - replacement of other tissues by bone.
Refers specifically to formation of bone.
two steps. ossification and
during ossification, but can occur in other tissues.
calcification/mineralization.
Calcification - deposition of calcium minerals. Occurs
Two types of ossification:
Intramembraneous ossification
Generally, there are two types of ossification as
Occurs in the deeper layers of dermis.
Normal : dermal bones (i.e., flat bones of the skull)
given in the slide.
Abnormal : hetero- or ectopic bones in connective tissues
Endochondral ossification
Gradual conversion of foetal cartilagenous ’bones’ into true
bony structures.
© Uwe Kersting, 2011
13
5. The regulation of tissue adaptation has been studied most extensively for bone
tissue. – What is the basic multicellular unit (BMU) of bone? Describe its geometry
and cycle of action.
BMU = osteon. Cycle of action happens in six phases
Idrætskader – 2011 – MiniModule 3/worksheet 1
Uwe Kersting
6. What are the two biological functions of bones?
haematopoesis (generation of blood cells in red bone marrow) and calcium storage
7. What is the primary mechanical function of tendons?
connect bone with muscle - transfer force from muscle to bone segments
8. What is the primary mechanical function of ligaments?
connect bone to bone – provide guidance to joints/joint movements
9. Joint cartilage is a specialized tissue covering the ends of the long bones. Describe
its structure and how it resists compression under loading.
It contains two meshes of collagen fibres (type II) and non-collagenous molecules,
mainly proteoglycans and hyaluronan acid. The PG bind water due to electrostatic
forces and develop repulsive force which withstand compression. The more the
tissue gets compressed the higher the forces. Fluid will only be displaced very
slowly from the cartilage body. See slides 38 – 42 for more detail.
10. Which type of training has been shown to reduce the number of ankle injuries in
team sports like basketball or soccer?
balance training and/or proprioceptive training
11. What are mechanical stress and strain?
stress () is load per area;  = Force/loaded area; It can be perpendicular to the
surface (pure compression); in this case it is simply pressure.
Strain = relative change in length/size. If an object (e.g., a string is 10 cm in length
(lo) and gets stretched by 1 cm (l) the strain () would be calculated as  = l / lo.
(The number would be the same if we measure the length in metres or inches (0.01
m / 0.1 m = 0.1; the result is always a unit-less number and can be expressed as
percentage. In this example the strain in the string would be 10%).
12. What is meant by Wolff’s law?
Given on slide 23. The historical definition was worded more statically. Research
has now shown that the dynamics of the applied loads also play an important role.
13. What is covered by the term ‘Mechanostat’?
It is a term introduced by Frost encompassing the overall effect of the processes
involved in tissue adaptation. It includes the terms physiological upper limit (PUL),
physiological lower limit (PLL), minimum effective strain (MES). The core idea is
that tissue strain during activity has to be higher than MES to cause an increase in
Idrætskader – 2011 – MiniModule 3/worksheet 1
Uwe Kersting
tissue mass. The increase in material will make the whole structure stronger and
with that reduce the strain at the same level of stress. Biological systems aim at
maintaining a balance between stress and strain.
14. What is visco-elasticity in comparison to pure elastic behaviour?
Elastic behaviour is simply spring-like behaviour. Force/stress in a structure is
proportionate to deformation (strain). If viscoelastic the deformation is velocitydependent and energy will be lost during each deformation. All biological tissues
are viscoelastic.