Medical Physics Chapter 4: Physics of the Skeleton

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What is the primary function of the ossicle bones in the middle ear?

Converting sound vibrations in air to sound vibrations in the fluid in the cochlea.

What is the functional role of bones in supporting the body?

Supporting muscles, for example, in the legs and vertebrae.

How do bones store chemicals, and what is an example of this?

Bones store chemicals, such as calcium, which is released when needed.

What is the role of teeth in the body, and how do they serve this purpose?

Teeth serve in providing nourishment for the body by cutting, tearing, and grinding food. Signup and view all the answers

How do bones contribute to the production of red blood cells?

Bones contribute to the production of red blood cells through the bone marrow. Signup and view all the answers

What is the number of bones in the adult human body, and what is the structure that holds them together?

The adult human body has 206 bones, held together by ligaments. Signup and view all the answers

What are the three components of bone composition?

collagen, bone mineral, and water Signup and view all the answers

What is the percentage of collagen in the weight of solid bone?

40% Signup and view all the answers

What is the chemical composition of bone mineral?

calcium hydroxyapatite (Ca10(PO4)6(OH)2) Signup and view all the answers

What are the five shapes of bones?

flat, plate-like; long, hollow; cylindrical; irregular; and other bones Signup and view all the answers

What is the difference between compact and cancellous bones?

compact bones are solid and stronger, while cancellous bones are spongy and weaker Signup and view all the answers

What are the two types of stress that can act on a bone?

tension and compression Signup and view all the answers

What is the main advantage of using an I-beam as a support beam?

using a less amount of material Signup and view all the answers

What is the relationship between stress and strain in the initial linear portion of the stress-strain curve?

proportional Signup and view all the answers

What is the purpose of the trabecular pattern at the ends of the femur and humerus?

to provide strength with a less amount of material for compression forces Signup and view all the answers

What is the function of the compact bone in the shaft of the femur?

to prevent buckling Signup and view all the answers

What is the advantage of trabecular bone in terms of energy absorption?

it absorbs more energy when large forces are involved Signup and view all the answers

What is Young's modulus (Y) a measure of?

the ratio of stress to strain in the initial linear portion Signup and view all the answers

What is a characteristic of trabecular bone compared to compact bone?

Trabecular bone is metabolically more active but less stiff and weaker than compact bone. Signup and view all the answers

What is the density of compact bone, and how does it change with age?

The density of compact bone is approximately 1.9 g/cm3, and it remains constant throughout life, but the bone becomes more porous and thinner with age, leading to reduced strength. Signup and view all the answers

What is the ultimate tensile stress of compact bone?

The ultimate tensile stress of compact bone is 120 N/mm2 or 17,000 Ib/in2. Signup and view all the answers

What is the force exerted on the hip bone during running and normal walking?

During running, the force on the hip bone is approximately four times the body weight, and during normal walking, it is approximately two times the body weight. Signup and view all the answers

What is the safety factor in most engineering design, and how does it relate to the ultimate compressive stress of healthy compact bone?

The safety factor in most engineering design is 10 times the maximum expected force, and the ultimate compressive stress of healthy compact bone is 170 N/mm2 before it fractures. Signup and view all the answers

What is the concept of viscoelasticity in relation to bone, and how does it provide a safety factor?

Viscoelasticity is the ability of bone to withstand a large force for a short period, providing a safety factor against fracture. Signup and view all the answers

What happens to the lubricant material in the articular cartilage when the joint is under stress?

The lubricant material is squeezed out of the articular cartilage into the joint. Signup and view all the answers

How does the viscosity of synovial fluid change under large shear stress?

The viscosity of synovial fluid decreases under large shear stress. Signup and view all the answers

What is the coefficient of friction of a healthy joint, and how does it compare to other materials?

The coefficient of friction of a healthy joint is less than 0.01, which is lower than that of a steel blade on ice. Signup and view all the answers

Why is it important to measure bone mineral mass in the body?

Measuring bone mineral mass is important for determining the strength of bone and evaluating therapy for osteoporosis. Signup and view all the answers

What are some of the limitations of using conventional X-rays to measure bone mineral mass?

The limitations include the X-ray beam having many different energies, X-ray scattering, and the non-linear characteristics of the film. Signup and view all the answers

What is the rate of bone mineral decrease in the body, and what is the resulting condition?

The rate of bone mineral decrease is 1-2% per year, leading to osteoporosis. Signup and view all the answers