Bone

Question 1

What is immature bone?

Answer 1

Bone with osteocytes fairly randomly arranged

Question 2

What is mature bone?

Answer 2

Bone with osteocytes arranged in concentric lamellae of osteons

Question 3

What is an osteon?

Answer 3

Cylindrical concentric layers of compact bone which surround haversian canal

Question 4

How does bone differ from cartilage?

Answer 4

It’s vascular

Question 5

Give three characteristics of bone

Answer 5

Can withstand stress, Responds to stress and strains via growth, Sensitive to pain, Contains cells, fibres and ground substance

Question 6

Give four functions of bone

Answer 6

SupportProtectionMineral storageHaemopoieses

Question 7

What are two forms of bone?

Answer 7

Compact and spongelike (dense and cancellous)

Question 8

What is haemopoiesis?

Answer 8

Formation of blood cellular components

Question 9

What is the structure of compact bone?

Answer 9

Osteons with central haversian canal, which communicate via volkmanns canals

Question 10

What is a haversian canal?

Answer 10

A neurovascular canal

Question 11

How do osteocytes connect to each other?

Answer 11

Caliculi

Question 12

What is spongy bone? (also known as cancellous and medullar bone)

Answer 12

Meshwork of trabeculae filled in with marrow

Question 13

Two different types of marrow?

Answer 13

Red - Red blood cell synthesisYellow - Adipose tissue

Question 14

What is marrow cavity lined with?

Answer 14

Endosteum

Question 15

What is endosteum?

Answer 15

Thin layer of connective tisswue which lines the medullarly cavity

Question 16

Where is the epiphysis of the bone?

Answer 16

The head

Question 17

What percentage of bone matrix is inorganic?

Answer 17

65%

Question 18

Name two inorganic salts found in bone matrix

Answer 18

matrix Calcium phosphate and Calcium Carbonate

Question 19

Where does bones hardness and rigidity come from?

Answer 19

Interaction between inorganic salts and collagen

Question 20

Where does bones flexibility come from?

Answer 20

Collagen fibres

Question 21

Where are Calcium and Phosphate stored in bone?

Answer 21

In the extracellular matrix

Question 22

What four things are calcium required for in the body?

Answer 22

Muscle contraction, blood coagulation, cell membrane permeability and nerve impulse transmission

Question 23

What does PTH do?

Answer 23

Stimulates osteoclasts to reabsorb bone matrix, releasing calcium into blood

Question 24

What happens when blood calcium levels higher than normal?

Answer 24

Calcitonin released, which inhibits osteoclast realse and decreases bone reabsorption

Question 25

What are the three bone cell types found in bone?

Answer 25

Osteoblasts, Osteoclasts and Osteocytes

Question 26

What is the function of osteoblasts?

Answer 26

Synthesise organic components of cells, making bone and produce the osteoid matrix.

Question 27

What are osteocytes?

Answer 27

What are osteocytes?

Question 28

How are osteocytes formed?

Answer 28

When osteoblasts are entombed to produce osteocytes.

Question 29

What are osteoclasts?

Answer 29

Large multinucleated cells from monocytes which digest bone

Question 30

What is periosteum and what is it made up of?

Answer 30

Two layers, connected by Sharpeys fibres. One dense collagenic outer layer, the other is more loosely arranged containing osteogenic cells and is referred to as osteogenic layer.

Question 31

Describe primary microstructure of bone, and give another name for it

Answer 31

Immature boneFirst bone to appear in the development and repair, it’s then replaced by mature boneCollagen fibres arranged in a random, interwoven fashionMore cells and less minerals

Question 32

Secondary microstructure of bone

Answer 32

Compact dense cortical boneSeries of Haversian Systems (osteons): consisting of concentric lamellae of bone laid around a central canal containing blood vessels.The spaces between Haversian systems are filled with bony lamellae (interstitial lamellae)The outer surface has extended lamellae (circumferential)Sponge-like cancellous medullaryBone, which is always surrounded by compact bone.It forms the meshwork of bone plates or trabeculae then the spaces are filled with marrow

Question 33

Give two ways in which bone develops

Answer 33

endochondral ossificationintramembranous ossification.

Question 34

Outline endochondral ossification

Answer 34

Cartilage is reabsorbed and replaced with bone (e.g. long bones)Begins at the primary centre in the shaft (diaphysis) and later at each end (epiphysis – secondary centre)Growth in length is at epiphyseal growth plates

Question 35

Outline intramembranous ossification

Answer 35

The bone begins as highly vascularised loose connective tissue.Mesenchymal cells differentiate  osteoblasts surrounded by collagen fibres and ground substance.They secrete uncalcified matrix (osteoid) and then become osteocytes

Question 36

How does bone remodel?

Answer 36

through the actions of osteoclasts and osteoblasts releasing and incorporating calcium into and from the matrix.

Question 37

Outline process of fracture repair

Answer 37

Break --> Haematoma --> Osteo Callus --> Primary Bone --> Secondary Bone1.Bone breaks2.Bone matrix is destroyed and the bone cells adjoining the fracture will die3.Inflammatory cells invade and form a pre-callus which contains a blood clot (haematoma) and fibrous tissue(If the periosteum is still intact a pro-callus is formed when the area is invaded by osteoclasts and macrophages which is more fibrous)4.An osteocallus of primary bone is made which is then calcified to secondary5.The bone is pulled and pressured to match the contours of the surrounding bone (mainly via tendons) and eventually forms mature bone6.Bone heals without forming a scar

Question 38

What are the zones in an epiphyseal growth plate?

Answer 38

Reserved cartilageProliferationHypertrophy Calcified cartilage Resorption

Question 39

Outline what happens in each zone of the epiphyseal growth plate.

Answer 39

Reserved cartilage -- no cell proliferation/matrix productionProliferation -- cells enlarge, divide to form columns and secrete matrixHypertrophy -- enlarge greatly, matrix composed between columnsCalcified cartilage -- cells degenerate, matrix calcifiedResorption -- matrix in direct contact w/ marrow cavity. Small blood vessels and connective tissue invade region of dying chondrocytes which leave calcified spicules. Bone is laid down on spicules