SLIDE 1 Connective Tissue and Bone
Peter Takizawa peter.takizawa@yale.edu
SLIDE 2 What we will talk about…
- Types and functions of connective tissue
- Cells of connective tissue
- Composition and structure of bone
- Cells that control the shape and integrity of bone
- Development of bone
SLIDE 3 Connective tissue serves a variety of functions throughout the body.
Resist stress Organize tissues Metabolic Connective Tissue Immunity
Fat cell Macrophage Bacterium
SLIDE 4 Connective tissue can generate a range of mechanical strengths.
Bone Tendon Cartilage Blood Vessels Organ Support
SLIDE 5 Connective tissue resists tension and compression.
Collagen Elastin Glycosamino- glycans
SLIDE 6 Connective tissue can be classified based on the amount and organization of collagen.
Dense Regular Dense Irregular Loose Collagen Collagen Glycoproteins
SLIDE 7 Reticular fibers are composed of type III collagen and organize cells in organs.
Reticular Fiber Cells
SLIDE 8 Adipose tissue contains adipocytes that store large amounts of lipid and triglycerides.
Nucleus Cytoplasm Lipids
SLIDE 9 Brown fat stores lipids and triglycerides and generates heat.
Nucleus Lipid Droplets
SLIDE 10
Cells of connective tissue
SLIDE 11 Fibroblasts are prominent in connective tissue and synthesize most of the protein components.
Collagen Collagen Fiber Fibroblast Areolar Tissue
SLIDE 12 Mast cells store and release histamine during an immune response
Mast Cell
SLIDE 13 Macrophage engulf foreign particles and cellular debris.
Macrophage
SLIDE 14
Cartilage
SLIDE 15 Chondrocytes synthesize cartilage which resists compression.
Chondrocyte Nucleus Matrix Lipid Droplets
SLIDE 16 Hyaline cartilage contains type II cartilage and glycosaminoglycans.
Toluidine Blue H&E Perichondrium Matrix Chondrocytes
SLIDE 17 Fibrocartilage contains a large amount of type I collagen.
Chondrocytes Collagen Fibers Matrix
SLIDE 18 Elastic cartilage contains elastic fibers and type II collagen.
Chondrocyte Elastic Fiber
SLIDE 19
Bone
SLIDE 20
Bone serves mechanical, metabolic and cellular functions. Ca2+
SLIDE 21 The major structure components of bone are calcium-phosphate crystals and type I collagen.
Ca2+ cyrstals Collagen Fibril Mineralized collagen fibril Composition of bone
SLIDE 22 Bone can be arranged in lamellar or woven forms.
Lamellar Woven
SLIDE 23
Architecture of bone
SLIDE 24 Compact bone and trabecular bone are two structures in most bones.
Compact Bone Trabecular Bone Periosteal Surface Endosteal Surface Diaphysis Epiphysis
SLIDE 25 Compact bone is organized into circumferential lamellae and Haversian systems.
Periosteal Surface Haversian Canal Volkmann’s Canal Circumferential bone Haversian system
SLIDE 26 Haversian Canal Volkmann’s Canal
SLIDE 27
Bone Cells
SLIDE 28
Osteoblasts secrete collagen and catalyze the crystallization of calcium on collagen fibers.
SLIDE 29 Osteoblasts synthesize osteoid that mineralizes into bone.
Osteoblast Bone Bone Osteoid O s t e
d
SLIDE 30 Osteocytes are osteoblasts that become trapped in bone matrix.
Osteoblast Osteocyte
SLIDE 31 Ground section of Haverisan System showing
- steocytes and their filopodia
Haversian Canal Osteocyte Filopodia
SLIDE 32 Osteocytes communicate via gap junctions on filopodia.
Filopodia Osteocyte Gap junction Bone Canalicullus
SLIDE 33
Osteoclasts
SLIDE 34 Osteoclasts secrete acid on bone to dissolve calcium-phosphate crystals.
CO2 H+ H+ H+ Cl- Cl- Cl- ATP ADP Pi CO2 H2O
CA
HCO3- Cl-
SLIDE 35
Osteoclasts secrete cathepsin K onto bone to digest collagen.
SLIDE 36
Transcytosis delivers digested bone matrix components to basal side of osteoclasts.
SLIDE 37 Histological image and electron micrograph showing an osteoclast
Bone Bone Osteoclast
SLIDE 38
Dynamics of bone turnover
SLIDE 39
Bone is a dynamic material that undergoes synthesis and resorption.
Synthesis Synthesis Resorption Resorption Increase length or store Ca2+ Increase Ca2+ levels Maintain integrity
SLIDE 40 Osteoblasts and osteoclasts reshape bone and replace old bone.
Reshape bone Bone modeling Replace bone Bone remodeling
Osteoblast Osteoclast
SLIDE 41
Bone modeling
SLIDE 42 Bone modeling shapes bone with osteoblasts and
- steoclasts working on different surfaces.
SLIDE 43
Trabecular bone aligns along lines of stress.
SLIDE 44 Periosteal apposition and endocortical resorption increase diameter of bone.
Seeman (2008) J Bone Miner Metab 26 1-8
SLIDE 45 Osteocytes use a primary cilium to detect mechanical stress in bone.
Primary cilium Ca2+ Fluid flow
SLIDE 46
Bone remodeling
SLIDE 47 Bone remodeling removes old bone and replaces it with new bone.
Compact bone Trabecular bone
SLIDE 48 Remodeling repairs bone with osteoclasts and
- steoblasts working on the same surface.
Activation/Resorption Reversal Formation
SLIDE 49 Basic multicellular unit consists of osteoclasts,
- steoblasts that remodel compact bone.
Kerr Atlas of Functional Histology 1st edition
Osteoclast Osteoblast
SLIDE 50 Remodeling erodes old Haversian Systems while forming new canals.
Resorption Formation
SLIDE 51
Development of osteoclasts
SLIDE 52 Pre-osteoclasts are activated by M-CSF and RANK ligand on the surface of osteoblasts.
Monocyte Preosteoclast Osteoclast Osteoblast
M-CSF
RANK-L RANK receptor
SLIDE 53 Osteoprotegerin is a decoy receptor for RANKL that prevents activation of preosteoclasts.
Monocyte Preosteoclast Osteoblast
M-CSF
Osteoclast
OPG RANK receptor
SLIDE 54 Parathyroid hormone stimulates osteoblasts to increases RANKL and decrease OPGs.
Ca2+ PTH Osteoblast
RANK receptor RANK-L
SLIDE 55 Estrogen has direct and indirect effects on the development and lifespan of osteoclasts.
Estrogen
Osteoblast
Estrogen Apoptosis OPG synthesis
SLIDE 56
Bone development
SLIDE 57 Intramembraneous ossification involves bone formation on mesenchymal tissue.
Mesenchyme Bone Osteocyte Osteoblast
SLIDE 58 Endochondrial ossification is bone formation on cartilage.
Cartilage Cartilage Bone Osteoid Bone Marrow Chondrocyte Growth Plate
SLIDE 59 The developmental sequence of chondrocytes drives bone formation in growth plates.
Resting Chondrocytes Proliferating Chondrocytes Hypertrophic Chondrocytes Calcified Cartilage
SLIDE 60 Take home points...
- The properties of connective tissue is determined by the and arrangement
type of ECM components and the cellular composition.
- Bones contain of compact bone and trabecular bone.
- Osteoblasts synthesize bone and osteoclasts dissolve bone.
- Osteocytes are mechanical sensors that regulate bone synthesis and
absorption.
- Bone modeling reshapes bone and bone remodeling replaces old bone.
- Increased activity and numbers of osteoclasts leads to osteoporosis.
