Skeletal System: Bones and Bone Tissue

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Chapter 6

• Skeletal SystemBones and Bone Tissue

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Skeletal System Functions

• Support
• Protection
• Movement
• Storage
• Blood cell production

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Hyaline Cartilage

• Consists of specialized cells that produce matrix
• Cells
• Chondroblasts
• Chondrocytes
• Perichondrium
• Articular cartilage
• Growth
• Appositional
• Interstitial

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Bone Shapes

• Long
• Upper and lower limbs
• Short
• Carpals and tarsals
• Flat
• Ribs, sternum, skull, scapulae
• Irregular
• Vertebrae, facial

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Long Bone Structure

• Diaphysis
• Shaft
• Compact bone
• Epiphysis
• End of the bone
• Cancellous bone
• Epiphyseal plate
• Growth plate
• Epiphyseal line
• Bone stops growing in length

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Long Bone Structure

• Medullary cavity
• Red marrow
• Yellow marrow
• Periosteum
• Outer bone surface
• Sharpeys fibers
• Attachment
• Endosteum
• Lines bone cavities

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Flat, Short, Irregular Bones

• Flat Bones
• No diaphyses, epiphyses
• Sandwich of cancellous between compact bone
• Short and Irregular Bone
• Compact bone that surrounds cancellous bone
  center
• No diaphyses and not elongated

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Bone Histology

• Bone matrix
• Organic Collagen and proteoglycans
• Inorganic Hydroxapatite
• Bone cells
• Osteoblasts
• Osteocytes
• Osteoclasts
• Stem cells or osteochondral progenitor cells
• Woven bone Collagen fibers randomly oriented
• Lamellar bone Mature bone in sheets
• Cancellous bone Trabeculae
• Compact bone Dense

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Bone Matrix
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Bone Cells

• Osteoblasts
• Formation of bone through ossification or
  osteogenesis
• Osteocytes
• Mature bone cells
• Lacunae Spaces
• Canaliculi Canals
• Osteoclasts
• Responsible for bone resorption

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Woven and Lamellar Bone

• Woven bone
• Formed
• During fetal development
• During fracture repair
• Remodeling
• Removing old bone and adding new
• Lamellar bone
• Mature bone in sheets called lamellae

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Cancellous Bone

• Consists of trabeculae
• Oriented along lines of stress

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Compact Bone

• Central or haversian canals Parallel to long
  axis
• Lamellae Concentric, circumferential,
  interstitial
• Osteon or haversian system Central canal,
  contents, associated concentric lamellae and
  osteocytes
• Perforating or Volkmanns canal Perpendicular to
  long axis

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Bone Development

• Intramembranous ossification
• Takes place in connective tissue membrane
• Endochondral ossification
• Takes place in cartilage
• Both methods of ossification
• Produce woven bone that is then remodeled
• After remodeling, formation cannot be
  distinguished as one or other

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Intramembranous Ossification
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Endochondral Ossification
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Endochondral Ossification
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Endochondral Ossification
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Growth in Bone Length

• Appositional growth
• New bone on old bone or cartilage surface
• Epiphyseal plate zones
• Resting cartilage
• Proliferation
• Hypertrophy
• Calcification

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Growth in Bone Length
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Growth in Bone Width
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Factors Affecting Bone Growth

• Nutrition
• Vitamin D
• Necessary for absorption of calcium from
  intestines
• Insufficient causes rickets and osteomalacia
• Vitamin C
• Necessary for collagen synthesis by osteoblasts
• Deficiency results in scurvy
• Hormones
• Growth hormone from anterior pituitary
• Thyroid hormone required for growth of all
  tissues
• Sex hormones as estrogen and testosterone

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Bone Remodeling

• Coverts woven bone into lamellar bone
• Bone constantly removed by osteoclasts and new
  bone formed by osteoblasts

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Bone Repair
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Calcium Homeostasis
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Calcium Homeostasis

• Bone is the major storage site for calcium in the
  body
• Calcium moves into bone as osteoblasts build new
  bone
• Calcium moves out of bone as osteoclasts break
  down bone
• When osteoclast and osteoblast activity is
  balanced, the movement of calcium in and out is
  equal

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Effects of Aging on Skeletal System

• Bone Matrix decreases
• Bone Mass decreases
• Increased bone fractures
• Bone loss causes deformity, loss of height, pain,
  stiffness
• Stooped posture
• Loss of teeth

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Bone Fractures