Bone Anatomy and Histology by Luis Filgueira
What is bone?
Connective Tissue
Cells <> Extracellular Matrix
Bone forming cells <> Bone resorbing cells Organic matrix <> Inorganic matrix Collagen <>Calcium apatite
Bone Tissue <> Bone Marrow
Function(s)?
What is cartilage?
Connective Tissue
Cells <> Extracellular Matrix Cells = Chondrocytes
Bone <> Cartilage
YES Calcified Matrix NO YES Blood vessels/nerves NO YES Repair/Remodelling NO
1 Bone = live tissue with high turnover = specialised connective tissue
Principles of connective tissue
Types of connective tissue 1. Embryonic connective tissue 2. Connective tissue proper 3. Fat tissue 4. Cartilage 5. Bone
Cells <> Extracellular matrix
Principles of connective tissue
Cells <> Extracellular matrix
Cells 1. Connective tissue proper <> Fibroblasts/fibrocytes 2. Fat tissue <> Adipocytes 3. Cartilage <> Chondrocytes 4. Bone <> Osteoblasts/osteocytes
Extracellular matrix produced and secreted by the cells 1. Ground substance 2. Fibres 3. Minerals 4. Water
Bone remodelling
Continuous adaptation of bone depending on Age Mechanics Hormones Nutrition
Formation of new bone tissue
Resorption of old bone tissue
Osteoblasts Osteoclasts
2 Addition/growth of bone = appositional growth
Osteoprogenitor cells are recruited onto the bone surface
Osteoblasts Arrange in a row on the surface of bone Produce new matrix = osteoid Enclose themselves inside the matrix
Osteoblasts become osteocytes New matrix is calcified
Differentiation and function of osteoclasts is under tight control of osteoblasts
Teitelbaum and Ross, Nature Reviews Genetics 2003, 4, 638
Osteoclasts
Haematopoietic Stem Cell
Erythrocyte Granulocyte
Blood Monocyte Lymphocyte
Osteoclast Macrophage Dendritic cell
3 What happens if there is no RANK?
Osteoblasts/osteocytes
Chondrocyte Stromal Stem Cell
Osteoprogenitor Cell Fibroblast
Osteoblast Muscle Cell
Fat Cell/Lipocyte
Osteocyte
3 principles of skeleton formation
Direct formation of bone tissue Embryonic bone formation = Bone remodelling intramembranous ossification Bone repair Formation of cartilage tissue = Only during embryology cartilage skeleton
First formation of cartilage model and secondary replacement of Embryonic bone formation cartilage by bone tissue = Bone growth enchondral ossification
4 Mesenchymal cells of head and neural crest
3 principles of skeleton formation
intramembranous ossification most of skull
cartilage skeleton Nose Ears Larynx Articular cartilage
enchondral ossification Axial skeleton Skeleton of limbs
Primary bone tissue <> Intramembraneous ossification Embryonic formation of most bones of the skull Bone repair
Differentiation of stem cells to osteoblasts
Production of Cells enclose extracellullar themselves into matrix the matrix
Osteoblasts become osteocytes Osteocytes = functional syncytium Matrix is calcified
5 First formation of cartilage model and secondary replacement of cartilage by bone tissue = enchondral ossification
Alcian blue / Alazarin red
Enchondral ossification
6 Osteoblasts/osteocytes
SOX9 Chondrocyte Stromal Stem Cell
RUNX2
Osteoprogenitor Cell Fibroblast
Osteoblast Muscle Cell
Fat Cell/Lipocyte
Osteocyte
Cbfa1/Runx2 Deficiency
7 Cbfa1/Runx2
Holoprosencephaly and cleidocranial dysplasia in a patient due to two positioneffect mutations
RUNX2 mutation
Osteoblasts/osteocytes
SOX9 Chondrocyte Stromal Stem Cell
RUNX2
Osteoprogenitor Cell Fibroblast PPAR
Osteoblast Muscle Cell
Fat Cell/Lipocyte
Osteocyte
8 Osteoblasts/osteocytes
SOX9 Chondrocyte Stromal Stem Cell
RUNX2
Osteoprogenitor Cell Fibroblast PPAR
Wnt Osteoblast Muscle Cell
Fat Cell/Lipocyte
Osteocyte
9 Oropharyngeal Skeletal Disease Accompanying High Bone Mass and Novel LRP5 Mutation
10 Why enchondral ossification?
1. Bone template of cartilage 2. Longitudinal growth 3. Articular cartilage
Most bones undergo enchondral ossification
Enchondral ossification
Epiphyseal growth plate <> Longitudinal bone growth
11 Bone Morphogenetic Protein BMP
Joints
Summary of cells and factors
Soluble Extracellular Factors
Nuclear Transcription Factors
12