Ch 1 Bone Structure & Response to Stress

Question 1

Purposes of the skeleton

Answer 1

1. Protect internal organs 2. Locomotion 3. Ca/P storage

Question 2

Major cell types

Answer 2

Osteoclasts Osteoblasts Osteocytes

Question 3

Two types of bone in the mature skeleton

Answer 3

1. Compact, cortical 2. Cancellous,, trabecular

Question 4

Advantage of having long bones

Answer 4

Increases moment arm thus more speed and power

Question 5

4 regions of an immature long bone

Answer 5

1. 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

Question 6

Role of the physis

Answer 6

responsible for the majority of long bone growth in young animals through endochondral ossification.

Question 7

Types of marrow (2)

Answer 7

Fatty or haemopoetic

Question 8

Site of most haemopoetic marrow

Answer 8

Metaphyseal cancellous bone & bones of the axial skeleton

Question 9

Layers of the periosteum (2)

Answer 9

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

Question 10

Where is periosteum located

Answer 10

Covering bones of the appendicular skeleton except in regions covered by articular cartilage, or where ligaments, tendons or joint capsules attach

Question 11

3 principal components of bone microstructure

Answer 11

1)Cellular 2) Organic extracellular matrix (ECM) 3) Inorganic portion of bone - hydroxyapatite

Question 12

Role of osteoblasts

Answer 12

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

Question 13

What are osteocytes

Answer 13

Osteoblasts (approx 10% of the population) which become enclosed within ECM/osteoid

Question 14

Main role of osteocytes

Answer 14

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.

Question 15

Major role of osteoclasts

Answer 15

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

Question 16

Components of the organic matrix (21% bone by weight)

Answer 16

Collagen (95% type 1) and proteoglycans/glycosaminoglycans (ground substance)

Question 17

Under what loading conditions is collagen strongest

Answer 17

Tension

Question 18

What is ground substance

Answer 18

Proteoglycans and their constituent glycosaminoglycans. Makes up 5% of organic matrix (other 95% collagen)

Question 19

Composition of proteoglycans

Answer 19

Core protein and covalently attached glycosaminoglycan side chains (GAG)

Question 20

Inorganic component of bone

Answer 20

Approx 71% of bone by weight, primarily calcium and phosphate Ca10(PO4)6(OH)2 - similar to synthetic hydroxyapatite crystals

Question 21

What is an osteon or Haversion system

Answer 21

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

Question 22

What is a cement line

Answer 22

Boundary of each osteone composed primarily of GAGs - weakest point of the bones microstructure

Question 23

Definition of osteoinduction

Answer 23

Induction of osteogenesis - seen with process of bone healing & involves recruitment and deveopment of preosteoblasts

Question 24

Definition of osteoconduction

Answer 24

The ability of bone to grown on the surface of an implant

Question 25

Definition of osseointegration

Answer 25

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