Bones structure and function

Question 1

through which two processes do bones change their structure?

Answer 1

modeling & remodeling

Question 2

why do bones undergo modeling?

Answer 2

to adapt to changing biomechanical forces

Question 3

why do bones undergo remodeling?

Answer 3

to remove old, microdamaged bone & replace it with new bone

Question 4

what are the 4 general categories of bone?

Answer 4

long bone, short bone, flat bone & irregular bone

Question 5

what are 2 examples of long bones?

Answer 5

tibia & femur

Question 6

what are 2 examples of short bones?

Answer 6

patella & tarsals

Question 7

what are 2 examples of flat bones?

Answer 7

ribs & scapulae

Question 8

what are 2 examples of irregular bones?

Answer 8

vertebrae & coccyx

Question 9

Name the 6 functions of the skeleton

Answer 9

structural support
permits movement - bones act as levers for muscles
organ protection
maintain mineral homeostasis & acid-base balance
bones act as a reservoir for growth factors and cytokines
environment for haematopoiesis

Question 10

what type of formation do long bones undergo?

Answer 10

membranous and endochondral

Question 11

what type of formation do flat bones undergo?

Answer 11

membranous

Question 12

describe the composition of long bones

Answer 12

diaphysis - hollow shaft of thick cortical bone
trabecular meshwork covered in thin cortical shell above growth plates (rounded epiphyses) and below growth plates (cone-shaped metaphyses)

Question 13

What are the physical properties of cortical bone?

Answer 13

It is dense and solid and is made up of haversian systems.

Question 14

What does cortical bone surround?

Answer 14

Marrow space.

Question 15

What is the haversian system wall made of?

Answer 15

Concentric lamellae.

Question 16

Which is more metabolically active - cortical bone or trabecular bone?

Answer 16

Trabecular bone.

Question 17

Name the outer surface of cortical bone and its function.

Answer 17

The periosteal - for growth and fracture repair.

Question 18

Name the inner surface of cortical bone and its function.

Answer 18

The Endosteal - has higher remodelling activity than periosteal due to more strain and cytokine exposure.

Question 19

Describe the structure of trabecular bone.

Answer 19

Honeycomb-like network of trabecular plates and rods.

Question 20

Where is trabecular bone found?

Answer 20

Interspersed in bone marrow.

Question 21

What structures are made from lamellar patterns?

Answer 21

Cortical and trabecular bone.

Question 22

What is a lamellar pattern?

Answer 22

Collagen fibrils laid down in alternating patterns.

Question 23

How is the structure of the Lamella pattern related to its function?

Answer 23

The alternating orientation of collagen fibrils makes the structure extremely strong.

Question 24

Describe the structure of woven bone.

Answer 24

There is no lamellar pattern. The collagen is disorganised.

Question 25

Is woven bone strong or weak?

Answer 25

weak

Question 26

What is woven bone?

Answer 26

The form of primary bone.

Question 27

What is the periosteum?

Answer 27

The fibrous connective tissues surrounding the cortical exterior.

Question 28

What is the function of the periosteum?

Answer 28

It contains blood vessels, nerve fibres, osteoblasts and osteoclasts.

Question 29

What is the endosteum?

Answer 29

The membrane of the inner cortical and trabecular bone and Volkmann canals.

Question 30

What is the function of the endosteum?

Answer 30

Contains vessels, osteoblasts and osteoclasts.

Question 31

Name the three ways in which bones change their shape and structure.

Answer 31

Growth modelling and remodelling.

Question 32

In which two ways can bone growth occur?

Answer 32

The longitudinally and radially.

Question 33

When does bone growth occur?

Answer 33

During childhood

Question 34

Describe the process of longitudinal growth.

Answer 34

Cartilage proliferates in epiphyseal and metaphyseal. It becomes mineralized and forms primary new bone. occurs at the growth plates.

Question 35

What is modelling?

Answer 35

When bones change shape due to physiologic influences or mechanical forces - the gradual adjustment of the skeleton to the forces it encounters.

Question 36

Why do bones widen with age?

Answer 36

It is the response to periosteal opposition of new bone and endosteal reabsorption of old bone.

Question 36

What is Wolff's law?

Answer 36

Long bones change shape to accommodate stress they're put under

Question 36

What happens during bone modelling?

Answer 36

Bones widen or change axis by adding and removing parts of the bone via osteoblast and osteoclasts.

Question 36

What is more frequent in adults - modelling or remodelling?

Answer 36

remodelling.

Question 36

What is remodelling?

Answer 36

It is the continuous removal of discrete packets of old bone. It is replaced with new proteinaceous matrix, which is then mineralized form bone.

Question 37

Why is remodelling important?

Answer 37

bone is renewed to maintain strength and mineral homeostasis.

Question 38

Why is it important that old bonus reabsorbed?

Answer 38

It prevents bone micro damage accumulation.

Question 39

At what stage in life does remodelling occur?

Answer 39

At all stages, from birth until death.

Question 40

What does a remodelling unit consist of?

Answer 40

A tightly coupled group of osteoclasts and osteoblasts, which reabsorbed and form bone.

Question 41

What is the 4 phase cycle of remodelling?

Answer 41

Activation reabsorption reversal and formation.

Question 42

What is meant by bone balance?

Answer 42

The difference in old bone reabsorption and new bone formation

Question 43

Describe the bone balance of periosteal.

Answer 43

Mildly positive.

Question 44

Describe the bone balance of endosteal.

Answer 44

Mildly negative.

Question 45

Describe the bone balance of trabecular bone.

Answer 45

Mildly negatives.

Question 46

What is the role of osteoclasts?

Answer 46

Osteoclasts reabsorb bone.

Question 47

What is the role of osteoblasts?

Answer 47

Osteoblasts synthesise new bone matrix on bone falling surfaces.

Question 48

What are osteocytes?

Answer 48

Differentiated osteoblasts located in the Lacunae of mineralised bone.

Question 49

List some of the roles of osteocytes.

Answer 49

Support bone structure and metabolism support protective lining cells that cover surface of quiescent bone. Can act as phagocytes. connexion to each other and bone surfaces mechanosensation.

Question 50

Why can osteocytes act as phagocytes?

Answer 50

They contain lysosomes.

Question 51

What are gap junctions?

Answer 51

Gap junctions link osteocytes metabolically and electrically and are needed for osteocyte maturation activity and survival.

Question 52

One of the roles of osteocytes is mechanosensation. What is this?

Answer 52

They transduced stress signals from bending and stretching bone to biologic activity to allow bone remodelling.

Question 53

how does apoptosis of osteocytes occur and what does this affect?

Answer 53

Gap junctions may be disrupted, which leads to less and less remodelling and thus weak bones.

Question 54

Describe bone composition.

Answer 54

50 to 70% minerals. 20 to 40% organic matrix 5 to 10% water < 3% lipids.

Question 55

What is the function of the inorganic matrix in bone?

Answer 55

Provides mechanical rigidity. It gives load-bearing strength.

Question 56

Describe mineralization of the inorganic matrix.

Answer 56

Minerals are deposited in hole zones between ends of collagen fibrils .

Question 57

Describe the composition of organic matrix.

Answer 57

85 to 90% collagen, 10 to 15% non collagenous.

Question 58

What type of collagens are present in organic matrix?

Answer 58

Type 1 type 3 type 5 and FACIT collagens.

Question 59

What is the role of FACIT collagens?

Answer 59

They act as molecular bridges to organise and stabilise extracellular matrices.

Question 60

What non-collagenous substances are present in organic matrix?

Answer 60

Proteoglycans, glycosylated proteins y-carboxylated proteins.

Question 61

What is the role of non-collagenous substances inorganic matrix?

Answer 61

Serve functions like mineral deposition, regulation and bone cell activity.