Bone histology

Question 1

Answer 1

a – Volkmann canals

b – perforating/Sharpey fibres

c – periosteum

d – outer circumferential lamella

e – osteocytes

f – intermediate lamellae

g – osteons

h – inner circumferential lamella

i – endosteum

j – bone marrow

k – spongey substance/substantia spongiosa

l – compact substance/substantia compacta

Question 2

Answer 2

a – osteocytes

b – lamellae of osteons

c – endosteum

d – inner circumferential lamella

e – bone marrow

f – Haversian vessels

g – periosteum

h – perforating/Sharpey fibres

Question 3

Answer 3

a – bone marrow

b – endosteum

c – inner circumferential lamella

d – Haversian vessels

e – lamellae of osteons

f – osteocytes

g – periosteum

h – perforating/Sharpey fibres

i – Volkmann canals

Question 4

Answer 4

a – Haversian vessels

b – lamellae of osteons

c – endosteum

d – Volkmann canals

e – bone marrow

Question 5

What is bone?

Answer 5

A matrix of intercellular material surrounding widely separated cells

Question 6

What is bone comprised of?

Answer 6

– 50% crystallised mineral

– Hydroxyapatite (Ca phosphate and Ca hydroxide) Ca10(PO4)6(OH)2

– Magnesium hydroxide

– Fluoride

– Sulphate

– 25% collagen fibres

– 25% water

Question 7

What is calcification?

Answer 7

Calcification is a process of crystallisation of minerals within a collagen framework

Question 8

What is the hardness of bones dependent on?

Answer 8

Minerals

Question 9

How can the minerals be removed from bone?

Answer 9

By soaking the bone in an acid

Question 10

What happens to mineral deficient bones?

Answer 10

They become flexible

Question 11

What done bone flexibility depend on?

Answer 11

Collagen

Question 12

What happens to bone when its collagen is removed?

Answer 12

It becomes brittle

Question 13

Diaphysis

Answer 13

(growing between) or shaft/body

Question 14

Epiphysis

Answer 14

(growing over) or ends of the bone

Question 15

Metaphysis

Answer 15

where diaphysis/epiphyses join

Question 16

Epiphyseal plate

Answer 16

Cartilaginous, during growth

Question 17

Epiphyseal line

Answer 17

Bony, after growth

Question 18

Periosteum

Answer 18

Outer sheath

Question 19

Medullary cavity

Answer 19

Containing yellow marrow

Question 20

Endosteum

Answer 20

Thin membrane lining medullary cavity

Question 21

Answer 21

a – proximal epiphysis

b – metaphysis

c – diaphysis

d – metaphysis

e – distal epiphysis

f – articular cartilage

g – humerus

h – nutrient artery in nutrient foramen

i – medullary cavity

j – periosteum

k – compact bone

l – endosteum

m – spongey bone

n – red bone marrow

o – epiphyseal line

p – articular cartilage

Question 22

Bone cell types

Answer 22

• Osteogenic cells
• Osteoblasts
• Osteocytes
• Osteoclasts

Question 23

Osteogenic cells

Answer 23

• Mesenchymal stem cells
• Only bone cells to undergo cell division
• Daughter cells are osteoblasts
• Found in

–Inner portion of periosteum

–Endosteum

–Blood vessel containing canals

Question 24

Osteoblasts

Answer 24

• Bone building cells
• Synthesise and secrete collagen/matrix
• Initialise calcification
• Become trapped in matrix
• Become osteocytes

Question 25

Osteocytes

Answer 25

* Mature bone cells * Main bone cells * Maintain daily bone metabolism * Exchange of nutrients/waste

Question 26

Osteoclasts

Answer 26

* Bone resorbing cells * Huge * Formed from monocyte fusion (up to 50) * Concentrated in the endosteum * Ruffled border facing bone surface –Releases lysosomal acids and enzymes –Breaks down protein/mineral parts of bone –Part of normal development/maintenance and repair of bone

Question 27

Answer 27

Osteogenic cell

Question 28

Answer 28

Osteoblast

Question 29

Answer 29

Osteocyte

Question 30

Answer 30

Osteoclast

Question 31

Function of osteogenic cell

Answer 31

Develops into an osteoblast

Question 32

Function of osteoblast

Answer 32

Forms bone matrix

Question 33

Function of osteocyte

Answer 33

Maintains bone tissue

Question 34

Function of ostoclast

Answer 34

Functions in resorption, the breakdown of bone matrix

Question 35

Compact bone tissue

Answer 35

* Few spaces * External layer of all bone * Makes up bulk of diaphyses of long bones * Protection and support * Surrounds yellow bone marrow

Question 36

Answer 36

a - proximal epiphysis b - spongey bone c - metaphysis d - medullary cavity in diaphysis e - compact bone

Question 37

Cancellous/spongy bone tissue

Answer 37

* Many spaces * Latticework of thin columns of bone (trabeculae) * Makes up most of short, flat and irregular bones * Epiphyses of long bones/medullary cavity of diaphyses * Trabeculae arranged around lines of stress * Lighter than compact bone * Supports red bone marrow

Question 38

Histology – compact bone

Answer 38

* Osteons (Haversian systems) * Transverse perforating (Volkmann’s) canals * Longitudinal central (Haversian) canals * Concentric lamellae (calcified matrix) * Lacunae (containing osteocytes) * Canaliculi (osteocyte projections / communication / nutrients)

Question 39

Answer 39

a – compact bone b – spongey bone c – medullary cavity d – periosteum e – interstitial lamellae f – outer circumferential lamellae g – concentric lamellae h – blood vessels i – lymphatic vessel j – canaliculi k – lacuna l – osteocyte m – periosteal vein n – periosteal artery o – outer fibrous layer of periosteum p – inner osteogenic layer of periosteum q – central canal r – perforating canal s – compact bone t – lymphatic vessel u – spongy bone v – inner circumferential lamellae w – trabeculae x – medullary cavity

Question 40

Histology – cancellous bone

Answer 40

* Trabeculae (no osteons or canals) * Osteocytes in trabecular lacunae with canaliculi * Osteocytes comparatively superficial and receive nourishment directly from blood circulating in medullary cavities

Question 41

Answer 41

a – enlarged aspect of spongey bone trabeculae b – details of a section of a trabecula c – trabeculae d – space for red bone marrow e – lacuna f – interstitial lamellae g – canaliculi h – osteoblasts aligned along trabeculae of new bone i – osteoclast j - osteocyte