Normal structure of bone and bone cells

Question 1

What type of tissue is bone?

Answer 1

Specialised form of living connective tissue

Question 2

How does the fibrous matrix in bone give it strength?

Answer 2

Allows bone to withstand high compressive loads

Question 3

What is stored in bone?

Answer 3

Mineral ions

Question 4

What is the most abundant mineral ion found in bone?

Answer 4

Calcium

Question 5

What are the 2 types of bone?

Answer 5

Cortical/compact bone

Cancellous/trabecular/spongy bone

Question 6

In cortical/compact bone, what is the proportion of bone compared to spaces?

Answer 6

High proportion of bone so there are few spaces

Question 7

In cancellous/trabecular/spongy bone, what is the proportion of bone compared to spaces?

Answer 7

Low proportion of bone so there are lots of spaces

Question 8

What type of bone causes a more severe bone fracture?

Answer 8

Cortical/compact

Question 9

Why is a cortical/compact bone fracture more severe in post-pubescents than children?

Answer 9

Children can still change and regenerate cortical bone, but post-pubescents can’t

Question 10

What is the trabeculae, that is found in trabecular bone?

Answer 10

Network of rods and plates

Question 11

How can the substance bone matrix be described?

Answer 11

Non-living, intercellular

Question 12

What component of bone makes up most of the bone mass?

Answer 12

Bone matrix

Question 13

What collagenous protein is present in the bone matrix?

Answer 13

Type 1 collagen

Question 14

What 3 non-collagenous proteins are present in the bone matrix?

Answer 14

Proteoglycan, osteocalcin, osteonectin

Question 15

What is the function of type 1 collagen in the bone matrix?

Answer 15

Assembles into triple-stranded fibres that form 3D scaffold for bone cells and tissues to develop from

Question 16

What are the 3 functions of proteoglycan in the bone matrix?

Answer 16

Aids regulation of collagen fibrogenesis, ion movement and forms compression-resistant networks between fibres

Question 17

What are the 2 functions of osteocalcin in the bone matrix?

Answer 17

Binds to calcium, aids bone endocrine function (that can also affect other organs)

Question 18

What is the function of osteonectin in the bone matrix?

Answer 18

Helps to influence bone mineralisation during formation as it binds HA and collagen so regulates calcium release (from HA)

Question 19

In woven bone, what are 3 characteristics of the collagen pattern?

Answer 19

Random fibre orientation, immature form as cross-links haven’t formed between collagen fibrils to produce tight fibres, large and numerous osteocytes

Question 20

What condition causes collagen to be laid down in an irregular way in woven bone?

Answer 20

Rapid new bone formation, such as in repair of a fracture

Question 21

What are the 2 types of mature lamellar bone?

Answer 21

Cortical or spongy bone

Question 22

Where is lamellar bone found in the body?

Answer 22

Almost whole of adult skeleton

Question 23

What units is lamellar bone made up of?

Answer 23

Lamellae

Question 24

In lamellae bone, is the collagen pattern in a distinct or random orientation?

Answer 24

Distinct

Question 25

In a long bone, what is the cortex made of?

Answer 25

Compact bone 'shell'

Question 26

In a long bone, what structure does the cortex cover?

Answer 26

Medullary/marrow cavity

Question 27

What is the medullary/marrow cavity function in a long bone?

Answer 27

Site of red marrow, where blood cells are produced in immature bone eg. children's bones

Question 28

In the medullary/marrow cavity of a long bone, what replaces the red marrow as the person ages?

Answer 28

Inactive yellow marrow

Question 29

What gives yellow marrow its colour?

Answer 29

Adipose tissue

Question 30

What is the diaphysis of a long bone?

Answer 30

Cylindrical shaft

Question 31

What is the epiphysis of a long bone?

Answer 31

Expanded end of the bone

Question 32

What is the metaphysis of a long bone?

Answer 32

'neck' region of bone that is between epiphysis and diaphysis

Question 33

What part of the epiphysis structure extends into the metaphysis structure in a long bone?

Answer 33

Spongy bone walls

Question 34

What structure does the metaphysis contain that is present in children (immature bone)?

Answer 34

Growth plate

Question 35

What happens to the growth plate in the metaphysis as the bone matures?

Answer 35

Growth plate ossifies to become epiphyseal line

Question 36

What is the periosteum of a long bone?

Answer 36

Thin layer of connective tissue that covers outer surface of bones except articular surfaces

Question 37

What part of the long bone isn't covered by the periosteum?

Answer 37

Articular surface

Question 38

What cells are present in the inner layer of the periosteum of long bones?

Answer 38

Osteoprogenitor/osteogenic cells

Question 39

What 2 structures are present in the outer fibrous layer of the periosteum of long bones?

Answer 39

Blood vessels, nerves

Question 40

What are Sharpey's fibres?

Answer 40

Periosteal collagenous fibres that protrude into bone matrix to bind periosteum to bone

Question 41

How do blood vessels and nerves in the outer fibrous layer of the periosteum travel to supply bone cells?

Answer 41

Pass through Haversian canal then Volkmann canals

Question 42

What is the endosteum of a long bone?

Answer 42

Cellular layer that covers inner surfaces of bone eg. lines medullary cavity of cortical bone, lines trabeculae in spongy bone

Question 43

In a osteon/haversian system, what is the name of the central canal?

Answer 43

Haversian canal

Question 44

What are the 4 bone cells?

Answer 44

Osteocyte, osteoblast, osteoclast, bone lining cell

Question 45

What are the 3 functions of osteoblasts?

Answer 45

Synthesis and mineralisation of bone matrix Secretion of osteoid Bone formation

Question 46

What is osteoid?

Answer 46

Unmineralised collagen-proteoglycan matrix that binds calcium, is the organic component of bone matrix

Question 47

What happens to the bone matrix when osteoid binds to calcium?

Answer 47

Bone matrix hardens and osteoblasts are trapped in lacunae, entrapment causes osteoblasts to change into osteocytes

Question 48

What is the shape of an osteoblast?

Answer 48

Cuboidal cell

Question 49

What are the 2 processes that require osteoblasts to contain many organelles?

Answer 49

Necessary for high amounts of protein synthesis and secretion

Question 50

What kind of layer do osteoblasts form on the bone surface?

Answer 50

Epithelioid layer

Question 51

What is the main function of bone lining cells?

Answer 51

They are inactivated osteoblasts on the bone surface that can be reactivated into active osteoblasts

Question 52

Why do bone lining cells and osteocytes co-operate?

Answer 52

Regulate calcium exchange from bone

Question 53

What are the 3 functions of osteocytes?

Answer 53

Regulate bone formation and resorption regulate calcium homeostasis detect mechanical stress due to extent of physical loading/strain

Question 54

How are osteocytes formed?

Answer 54

Osteoblasts trapped in lacunae in bone matrix during apposition (increase in bone diameter), and can't secrete osteoid anymore so become osteocytes

Question 55

How are osteocytes in the bone matrix interconnected?

Answer 55

They have long dendritic processes that reach other osteocytes

Question 56

What is a canaliculi?

Answer 56

Narrow channel radiating from lacunae in bone matrix that contain osteocyte dendritic processes inside them, and connects with haversian canal in the osteon/haversian system

Question 57

What is the function of the canaliculi?

Answer 57

Allows diffusion of nutrients and waste between osteocytes and blood vessels

Question 58

What is the function of osteoclasts?

Answer 58

Bone resorption

Question 59

What is the structure of osteoclasts?

Answer 59

Large, polymorphic/multinucleated cell

Question 60

What are the organic and inorganic components of bone matrix?

Answer 60

Organic: Osteoid Inorganic: HA

Question 61

How is the ruffled border of the osteoclast formed?

Answer 61

Deep membrane invaginations to form finger-like processes

Question 62

What is the function of the ruffled border of the osteoclast?

Answer 62

It is on the lower part of the osteoclast, that faces bone surface to secrete acid and proteases to break down bone

Question 63

What is the function of the clear/sealing zone of the osteoclast?

Answer 63

Contains actin filaments to anchor osteoclast to bone