8977 Lecture 2: Bone
3 Jul 2018
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Functions of the Skeleton
- Supportive framework: rigid anchor
- Movement: using bones as levers
- Protection: of CNS, thoracic and abdomino-pelvic organs
- Mineral store: of calcium and phosphate ions
- Blood cell production: RBC’s and WBC’s, marrow the site of immunogenic activity
MACROSCOPIC Bone Anatomy
Compact Bone (Cortical Bone)
- Found in outer layers of diaphysis and flat bones
- Haversian canals – vertical canals for blood vessels
-Volkman canals – horizontal:
oAllow communication
oCome to surface of the bone
-Osteon (Haversian system):
oLamellae: each ring around hole
oLacunae: contain osteocytes (that convert to osteoblasts)
oCanaliculi: canals between lacunae, allow osteocytes to pass info, waste and
O2.
Trabecular Bone (Cancellous Bone)
- Spongy bone
- Meshwork of few thick layers
- All spaces lined with endosteum and filled with marrow.
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COMPACT BONE
SPONGY BONE
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MICROSCOPIC Bone Anatomy
Osteoprogenitor cells:
- Osteoblasts
- Osteocytes (osteoblasts trapped in bone matrix)
- Osteoclasts
Matrix
- Collagen fibres, glycoproteins, calcium salts
- Lamelli – layers of matrix
- Lacunae – spaces for osteocytes
- Canaliculi – connect lacunae
Fat cells
Hematopoietic cells
- RBC
- WBC
Bone Remodelling
- Constant turnover = adaption to load
- Starts with bone resorption by osteoclasts
- Release of osteocytes within osteon, form osteoblasts to lay down new bone
- Muscle pull = significant stimuli
- Load rate, compression, tension, traction = specific cell responses
Ossification
- Laying down bone
- Osteoblasts secrete matrix
- Endochondral
oHyaline cartilage bone
oLong bone growth
oEpiphyseal plate bone growth
- Intramembranous
oFlat bones, skull, face, scapula, ribs
oFibrous tissue bone
oOsteoblasts lay down spicules of bone which coalesce to form sheets of bone
Osteoporosis
- Osteoclasts more active > osteoblasts
- D. bone mass, density, becomes porous + easy to break
- Caused by ageing + hormonal changes
oW more affected than M
oD. calcium fibres = ^ salts
oThin cortical bones
oHaversian canals ^ in diameters = cant withstand stresses
o^ porosity
othinning articular cartilage
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Document Summary
Mineral store: of calcium and phosphate ions. Blood cell production: rbc"s and wbc"s, marrow the site of immunogenic activity. Found in outer layers of diaphysis and flat bones. Haversian canals vertical canals for blood vessels. Volkman canals horizontal: allow communication, come to surface of the bone. Osteon (haversian system): lamellae: each ring around hole, lacunae: contain osteocytes (that convert to osteoblasts, canaliculi: canals between lacunae, allow osteocytes to pass info, waste and. All spaces lined with endosteum and filled with marrow. Release of osteocytes within osteon, form osteoblasts to lay down new bone. Load rate, compression, tension, traction = specific cell responses. Endochondral: hyaline cartilage bone, long bone growth, epiphyseal plate bone growth. Intramembranous: flat bones, skull, face, scapula, ribs, fibrous tissue bone, osteoblasts lay down spicules of bone which coalesce to form sheets of bone. D. bone mass, density, becomes porous + easy to break. Articular vs extra-articular (does it involve the joint)
