Ch 1 Bone Structure & Response to Stress Flashcards
Purposes of the skeleton
- Protect internal organs 2. Locomotion 3. Ca/P storage
Major cell types
Osteoclasts Osteoblasts Osteocytes
Two types of bone in the mature skeleton
- Compact, cortical 2. Cancellous,, trabecular
Advantage of having long bones
Increases moment arm thus more speed and power
4 regions of an immature long bone
- Diaphysis (central) 2. Metaphysis (periphery of the diaphysis) 3. Physis - separates Metaphysis and epiphysis at 1 or both ends 4. Epiphysis - at the End of long bones
Role of the physis
responsible for the majority of long bone growth in young animals through endochondral ossification.
Types of marrow (2)
Fatty or haemopoetic
Site of most haemopoetic marrow
Metaphyseal cancellous bone & bones of the axial skeleton
Layers of the periosteum (2)
1) Outer fibrous layer - permeated by blood vessels and nerves which act in a supportive capacity 2) Inner osteogenic layer - provides the osteoprogenitor cells necessary for fracture healing and appositional growth prior to skeletal maturity
Where is periosteum located
Covering bones of the appendicular skeleton except in regions covered by articular cartilage, or where ligaments, tendons or joint capsules attach
3 principal components of bone microstructure
1)Cellular 2) Organic extracellular matrix (ECM) 3) Inorganic portion of bone - hydroxyapatite
Role of osteoblasts
cover the majority of bone surfaces and are responsible for the formation of the organic matrix, called osteoid Osteoblasts produce the majority of the organic components of bone, including collagen, proteo- glycans, and other noncollagenous proteins
What are osteocytes
Osteoblasts (approx 10% of the population) which become enclosed within ECM/osteoid
Main role of osteocytes
Form an intricate interconnection system. They have numerous cytoplasmic processes that extend into the surrounding matrix and fill the canaliculi of bone, which contact the processes of other osteocytes and osteoblasts to form an intricate transport and communication system within the bone.
Major role of osteoclasts
Bone resorption - large multinucleate cells originating from monocytes. Produce acid phosphatase and collagenase to first dissolve mineral and then remove the organic matrix to a depth of 1–2 μm
Components of the organic matrix (21% bone by weight)
Collagen (95% type 1) and proteoglycans/glycosaminoglycans (ground substance)
Under what loading conditions is collagen strongest
Tension
What is ground substance
Proteoglycans and their constituent glycosaminoglycans. Makes up 5% of organic matrix (other 95% collagen)
Composition of proteoglycans
Core protein and covalently attached glycosaminoglycan side chains (GAG)
Inorganic component of bone
Approx 71% of bone by weight, primarily calcium and phosphate Ca10(PO4)6(OH)2 - similar to synthetic hydroxyapatite crystals
What is an osteon or Haversion system
Fundamental unit of bone - centre is a small channel, (Haversian canal), that contains vessels, nerves, and lymphatics. Surrounding the central canal is a concentric series of lamellae, of mineralised bone. Along the boundaries of each lamella are small spaces or lacunae, each of which contains individual osteocytes. Canaliculi radiate from these lacunae and connect with adjacent lamellae before ultimately reaching a Haversian canal
What is a cement line
Boundary of each osteone composed primarily of GAGs - weakest point of the bones microstructure
Definition of osteoinduction
Induction of osteogenesis - seen with process of bone healing & involves recruitment and deveopment of preosteoblasts
Definition of osteoconduction
The ability of bone to grown on the surface of an implant
Definition of osseointegration
Relationship between bone and the implant; direct structural and functional connection between the living bone and surface of a load-bearing implant such that the 2 cannot be separated without fracture
