LS2Lect19bone

LS2Lect19bone - Life Sciences 2 October 20 , 20 10...

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Unformatted text preview: Life Sciences 2 October 20 , 20 10 Musculoskeletal growth and development Readings: Chap. 16 Professor Daniel E. Lieberman Office hours Tuesday 2-3 Peabody 53 and by appointment : danlieb@fas.harvard.edu TODAY: The problem of the skeletal system Why have bones? How do bones function and change while growing? Bone structure Bone growth & adaptability Other connective tissues Osteoporosis FRIDAY: how it grows along with the rest of the body Why have bones? Function #1 PROVIDE STIFFNESS! = resistance to deformation Oppose gravity Permit muscles to generate movement Protect organs (e.g. brain, thorax) ouch! = Strain ( L/L) =Stress (F/A)* Stiffness, E = slope of stress vs strain (y/x) AKA Modulus of Elasticity (or Youngs modulus) f y f y y f e l a s t i c p la s t ic y = yield f = fracture *unit = Pascals (N/m 2 ) What is stiffness? y x Strain ( L/L) Stress (F/A) very stiff very flexible intermediate To stay stiff, bone must also be strong Stress to generate plastic deformation: y Stress to generate fracture: f Strain ( L/L) weaker stronger Strength = resistance to deformation or fracture =Stress (F/A) f y y f f y Function #2: be strong 99% of bodys calcium in bone Function #3: store calcium Haematopoesis (in bone marrow) Function #4: make blood cells Function #5: permit muscle to generate movement at joints These functions pose an interesting problem: How do you stay stiff, strong, permit movement, store calcium & make blood while changing in size and shape? A thought experiment: How would you grow a robot while enabling the robot to function during growth? How would you enable its structure to change as its functions changed? Evolutions answer = bone A stiff, strong, dynamic tissue that is highly modifiable Imagine you had to design a robot to G R O W The problem of the skeletal system Why have bones? How do bones function and change while growing? Bone structure Other connective tissues Bone growth & adaptability Osteoporosis To the naked eye (macrostructurally) there are two types of bone Compact (cortical) vs. Trabecular (spongy / cancellous) All made of the same tissue Bone = two phase substance Organic: Collagen Mineral: Calcium phosphate Also some H 2 O + NCPs (non-collagenous proteins) Collagen:...
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LS2Lect19bone - Life Sciences 2 October 20 , 20 10...

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