Adaptation in Bone Structure
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Questions and Answers

What is the formula for normal stress in a straight rod under tension?

  • s = F/A (correct)
  • s = A/F
  • s = F - A
  • s = F + A

    • How is tensile stress characterized in terms of forces acting on a material?

  • It involves forces pulling away from each other. (correct)
  • It involves unchanging forces with no stress.
  • It involves equal forces compressing from both ends.
  • It involves opposing forces pushing towards each other.

    • What is true about shear stress in comparison to normal stress?

  • Shear stress cannot exist in elastic materials.
  • Shear stress acts perpendicular to the surface.
  • Shear stress acts parallel to the surface. (correct)
  • Shear stress is always greater than normal stress.

    • In a situation where a rod experiences compressive stress, how does the sign of force and stress change?

    <p>The force remains positive, but stress becomes negative.</p> Signup and view all the answers

    What happens to the stress across a plane S that is perpendicular to the layer in simple shear stress equilibrium?

    <p>The stress is zero across the plane.</p> Signup and view all the answers

    What type of stress occurs when forces are applied perpendicularly to a material?

    <p>Normal stress</p> Signup and view all the answers

    When cutting a soft metal with scissors, which type of stress is primarily at work?

    <p>Shear stress</p> Signup and view all the answers

    What must be true about the forces acting on a straight rod in equilibrium?

    <p>They must be equal in magnitude and opposite in direction.</p> Signup and view all the answers

    What condition must be satisfied for the matrix $(s - spI)$ to have a nontrivial solution?

    <p>The determinant of the matrix must be zero.</p> Signup and view all the answers

    Which of the following represents the principal stresses?

    <p>$sp1$, $sp2$, $sp3$</p> Signup and view all the answers

    What is the role of the trace of the stress matrix in stress analysis?

    <p>It measures the tendency for hydrostatic dilation or compression.</p> Signup and view all the answers

    How do the principal stresses change when the coordinate system is rotated?

    <p>They remain unchanged.</p> Signup and view all the answers

    What does the equation $s_{xx} - s_{yy} = -2(s_{xy} \sin 2\theta)$ determine in terms of stress?

    <p>Condition for normal stress to disappear.</p> Signup and view all the answers

    What parameter contributes to hydrostatic dilation or compression as indicated by the trace of the stress matrix?

    <p>The average of $s_{xx}$ and $s_{yy}$.</p> Signup and view all the answers

    What happens to the shear stress component in a pure shear state?

    <p>It becomes zero.</p> Signup and view all the answers

    Which aspect of the stress state remains invariant under coordinate transformation?

    <p>The trace of the stress matrix.</p> Signup and view all the answers

    What factors influence the homeostatic bone mass when the amount of bone resorbed per volume remains constant?

    <p>Osteocyte mechanosensitivity</p> Signup and view all the answers

    What is one of the primary challenges in bone tissue engineering?

    <p>Matching the hierarchical organization of bone</p> Signup and view all the answers

    What does the term 'mechanical feed-back' refer to in the context of bone mass regulation?

    <p>Response of bone tissue to mechanical stimuli</p> Signup and view all the answers

    Which of the following is NOT a factor mentioned as influencing homeostatic bone mass?

    <p>Rate of calcium absorption</p> Signup and view all the answers

    What is a primary goal of tissue engineering when creating a bone scaffold?

    <p>Promoting cell adhesion and communication</p> Signup and view all the answers

    What is the role of osteoblasts in the context of bone mass and tissue engineering?

    <p>They are important for bone formation.</p> Signup and view all the answers

    What does the stimulus distance attenuation function (fi) refer to?

    <p>How mechanical stimuli affect the bone from a distance.</p> Signup and view all the answers

    What was the primary purpose of the study involving the Wistar rats?

    <p>To assess the mechanical properties of engineered tissues</p> Signup and view all the answers

    What materials were used in the implantation of the scaffolds?

    <p>Bioresorbable poly(L-lactic acid) and two ceramic powders</p> Signup and view all the answers

    At what frequency and magnitude was the loading applied to the right knee joint of the rats?

    <p>4 Hz and 10 N</p> Signup and view all the answers

    What characterizes hypothesis I regarding the probability of resorption, p?

    <p>It is equal for all surface sites.</p> Signup and view all the answers

    How often were the animals loaded during the study?

    <p>Every other day for 10 days</p> Signup and view all the answers

    What primarily triggers local osteoclast activation in hypothesis II?

    <p>Signal of mechanical disuse in the bone matrix.</p> Signup and view all the answers

    What measurements were taken using MicroCT during the study?

    <p>Bone fraction, mineral fraction, and bone formation rate</p> Signup and view all the answers

    What was the purpose of perfusing the scaffolds with PBS before implantation?

    <p>To remove air bubbles</p> Signup and view all the answers

    How does a 20% reduction in external loading affect trabecular thickness and bone mass?

    <p>Reduces trabecular thickness while causing a 15.8% loss in bone mass.</p> Signup and view all the answers

    What effect does a 20% increase in loads have on bone mass?

    <p>Increases bone mass by 17.5%.</p> Signup and view all the answers

    What does Finite Element Modeling in this study help compute?

    <p>The in vivo stiffness of the implanted construct</p> Signup and view all the answers

    What surgical procedure was performed on the rats before implantation of the scaffolds?

    <p>A hole was drilled into the femur</p> Signup and view all the answers

    What is the distinction in the kinetics of the remodeling process between the two hypotheses?

    <p>Hypothesis II develops a homeostatic architecture much faster than hypothesis I.</p> Signup and view all the answers

    What describes the end state of the homeostatic architecture after adjusting external loads?

    <p>It gradually returns to the original configuration.</p> Signup and view all the answers

    In terms of architecture, what is a distinct characteristic of trabecular architecture?

    <p>It aligns with the external load during remodeling.</p> Signup and view all the answers

    What primarily influences the total mass in the homeostatic architecture over time?

    <p>The balance between resorption and formation.</p> Signup and view all the answers

    What role do osteocytes play in the bone remodeling process?

    <p>They act as mechanosensors transmitting signals.</p> Signup and view all the answers

    What triggers the recruitment of osteoblasts during bone remodeling?

    <p>An increase in local strain due to external forces.</p> Signup and view all the answers

    How does bone remodeling affect local strain around resorption cavities?

    <p>It alters strain in a way that promotes further remodeling.</p> Signup and view all the answers

    Which cells are thought to differentiate into new osteocytes after the bone formation process?

    <p>Entrapped osteoblasts.</p> Signup and view all the answers

    What mechanism underlies the interaction between osteoblasts and osteoclasts?

    <p>A mechanical coupling factor.</p> Signup and view all the answers

    What is the primary effect of increased external forces on bone structure?

    <p>It induces strain that encourages bone modeling.</p> Signup and view all the answers

    What computational method was used to evaluate local strain perturbations in the study?

    <p>Finite-element methods of stress analysis.</p> Signup and view all the answers

    What is the function of lining cells in relation to osteocytes?

    <p>They help transmit signals from osteocytes to other cells.</p> Signup and view all the answers

    Study Notes

    Adaptation in Bones

    • Bones are a strong but lightweight material
    • Bones adapt their internal structure via mechanosensitive cells
    • Different bones have different functions adapted to their specific biological and physiological needs, like locomotion
    • Bone structure evolved as organisms became mobile on land, influencing the creation of new species eventually humans
    • Bone tissue engineering aims to improve human life

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    Bone Adaptation PDF

    Description

    Explore the fascinating world of bone adaptation and evolution in this quiz. Learn how bones serve various functions and how mechanosensitive cells contribute to their structural changes. Additionally, discover the potential of bone tissue engineering in enhancing human life.

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