Skeletal Skeletal System System Structure & Function Development & Growth Bone Homeostasis Osteoporosis & other bone disorders The evil that men do lives after them the good is oft interred with their b —William Shakespeare (1564-1616) Julius Caesar, Act III, Scene 2
Skeletal System. Structure & Function Development & Growth Bone Homeostasis Osteoporosis & other bone disorders. The evil that men do lives after them, the good is oft interred with their bones. —William Shakespeare (1564-1616) Julius Caesar, Act III, Scene 2. - PowerPoint PPT Presentation
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Skeletal Skeletal SystemSystem
Structure & Function Development & Growth Bone Homeostasis Osteoporosis & other bone disorders
The evil that men do lives after them, the good is oft interred with their bones.
—William Shakespeare (1564-1616) Julius Caesar, Act III, Scene 2
A Bone’s Shape Makes Possible A Bone’s Shape Makes Possible its Functionsits Functions
Sites of muscle attachments
• Shape & form
• Support
• Protection
• Movement
• Storage
• Hematopoiesis
Bone StructureBone Structure
Structures of a long bone:– periosteum: tough fibrous membrane covering
– diaphysis: shaft - b/t epiphyses, long axis of bone
– articular cartilage: portion of epiphysis covered w/ cartilage
– epiphysis: expanded ends of bone -- proximal & distal
Stages in Endochondral Stages in Endochondral Ossification Occurring in a Ossification Occurring in a
Long BoneLong Bone
EndochonEndochondral dral
OssificatioOssificationn
Forming skeleton of an embryonic chicken, stained with Alizarin Red and Alcian Blue to differentiate between hardened bone (in red) and the remaining cartilage model (in blue).
Bone Growth : elongation & Bone Growth : elongation & appositionalappositional
Hormonal Control of CaHormonal Control of Ca++++ BalanceBalance
• Parathyroid hormone (PTH) – responsible for plasma [Ca++]– mobilize Ca++ from bone ( bone resorption)– enhances renal reabsorption of Ca++ – intestinal absorption of Ca++ (indirectly)
• Vitamin D3 – 1,25-dihydroxycholecalciferol (calcitriol):– obtained from diet & sunlight– supports effect of PTH – enhancing Ca++ uptake in small
intestine– PTH & prolactin regulate production
• Calcitonin:– released in association w/ plasma [Ca++]– bone resorption & renal excretion (action opposite to PTH)
Factors Affecting Bone Factors Affecting Bone Development, Growth & Development, Growth &
RepairRepair Nutrition: calcium, phosphorus, vitamins D, A, C & K
UV radiation: dehydrocholesterol
Hormones: hGH, T3 & T4, PTH and male & female sex hormones
Bone Mineral Bone Mineral Acquisition During Acquisition During PubertyPuberty
Gap in CaGap in Ca++++ Intake Intake
• Females reach 95% of adult BMD by age 18 yrs & w/ only modest gains up to 3rd decade of life
• Bone mineral density (BMD) most rapidly b/t ages of 11-14 yrs in girls & 14-17 yrs in boys
• 86% of girls & 65% of boys aged 12-18 yrs fail to meet RDA of 1200 mg/d for Ca++
• Intake for Ca++ -- 1300 mg/d; gap b/t the recommended & actual intakes has widened
• Ca++ content of common foods: http://www.nof.org/
• Meeting RDA of Ca++ is challenging when dairy products are not consumed. Ca++ -fortified products offer a means of boosting Ca++ consumption through nondairy foods
• Nondairy sources of Ca++ such as breads, cereals, vegetables, and fish, have a lower content or less bioavailable form. Ca++ -rich foods such as DGLV, tofu, nuts, legumes & sardines are not part of the standard diet
• Inadequate vitamin D intake, lack of exposure to sunlight & reduced vitamin D receptors in older adults all contribute
• Lack of phys. act., smoking, excessive alcohol consumption, diets Na & phosphorus
Barriers to Calcium Intake & Other Barriers to Calcium Intake & Other Factors Affecting Bone Mineral Factors Affecting Bone Mineral DensityDensity