Transcript Mineralized Tissues

Mineralized Tissues
• Include bone, cartilage, dentin and enamel
• Specialized connective tissue
• Originate from mesenchymal cells that are
from the mesoderm
Cartilage
• Cells: chondroblasts give rise to
chondrocytes (mature).
• Fibers: collagen (type II), elastic and
reticular
• Ground substance: glycosaminoglycans
(hyaluronic acid, chondroitin sulfates) and
proteoglycans.
• Chondrocytes secrete extracellular matrix
(ECM) and become embedded in lacunae.
• Cartilage is avascular - exchange occurs by
diffusion across ECM.
• Growth - appositional (from the edges) and
interstitial (from within).
Types of cartilage:
• Hyaline
• Elastic
• Fibrocartilage
Bone
• Osteoblasts give rise to osteocytes
• ECM of collagen (type I) and
hydroxyapatite crystals (calcium phosphate)
• Osteoclasts resorb bone
Types of Bone
• Compact: lamallar structure. Organizational
unit is the osteon. Haversial canal supplies
blood vessels. Osteocytes in lacunae
communicate via cytoplasmic projections
within canaliculi. Periosteum contains
osteoblasts.
• Spongy: same elements as compact bone.
Irregular lamellae without osteons.
Framework of marrow cavity.
• Acellular bone: no canaliculi or processes.
Enamel, cementum and dentin of teeth; also
plates of scales inteleosts.
Ossification
Bone deposition is appositional
• Intramembranous: bone forms from
mesenchyme. Dermal bone and parts of jaw,
skull and pectoral girdle. Both compact and
spongy.
• Endochondral: osssification of preexisting
cartilage. Responsible for growth of long
bones. Remodeling is constant feature.
Bone Remodeling
• Regulated by genes and by mechanical
stress.
• Growth requires remodeling
• Osteoclasts
Connecting Elements
• Tendons: attach muscle to bone
• Ligaments: attach bone to bone
• Aponeurosis: broad flat sheet of tendon or
ligament
• Tendons and ligaments insert into bone by
means of Sharpey’s fibers
Articulations
Union of bones or cartilage
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Synarthrosis: little movement
Amphiarthrosis: limited movement
Diarthrosis: free movement. Synovial
Ankylosis: bone fused to bone (no a joint)