Bone

Question 1

Functions of bone

Answer 1

Support, lever for effective movement, protection of internal organs, calcium store and haemopoiesis

Question 2

How much calcium is found within bone

Answer 2

About 95% of total body calcium

Question 3

Composition of bone

Answer 3

65% biopatite, 23% collagen, 10% water, and 2% non-collagen proteins

Question 4

Fibrous connective tissue surrounding bone is known as

Answer 4

Periosteum

Question 5

What are the two types of bone

Answer 5

Cortical bone and cancellous bone

Question 6

What type of bone makes up the shaft

Answer 6

Cortical bone

Question 7

What type of bone makes up the ends of bone

Answer 7

Cancellous bone

Question 8

What is the main difference between the morphology of cortical and cancellous bone

Answer 8

The presence of spaces, known as marrow cavities, adjacent to cancellous bone

Question 9

Bone that is made up from layers is known as

Answer 9

Lamellar bone

Question 10

What is within the small canals in bone

Answer 10

Blood vessels and nerves

Question 11

What are the cells living within bone called

Answer 11

Osteocytes

Question 12

Characteristics of trabecular bone

Answer 12

• Has osteocytes
• Lamellar in nature
• Haversian canals are uncommon

Question 13

The outer layers of bone are organised in lamellae that run around the bone and are called

Answer 13

Outer circumferential lamellae

Question 14

What are the cells found within bone

Answer 14

Osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts

Question 15

Osteoprogenitor cells

Answer 15

• Located on bone surfaces under the periosteum

- Reserve pool of osteoblasts

Question 16

Osteoblasts

Answer 16

• Bone forming cells
• Found in the surface of developing bone
• Plentiful RER and prominent mitochondria

Question 17

Osteocytes

Answer 17

A bone cell trapped within the matrix

Question 18

Osteoclasts

Answer 18

• Large multinucleate cells
• Found on the surface of bone
• Responsible for bone resorption

Question 19

How do osteoblasts produce new bone

Answer 19

They actively secrete a matrix onto the top of pre-existing bone

Question 20

What is the main make up of the mineral of bone

Answer 20

Calcium phosphate crystals

Question 21

What do osteoblasts secrete

Answer 21

Collagen, GAGs, proteoglycans, and other organic compounds

Question 22

What is osteoblast secretion known as

Answer 22

Osteoid

Question 23

Other than osteoid, what else do osteoblasts secrete

Answer 23

Matrix vesicles

Question 24

What do matrix vesicles contain

Answer 24

Enzymes which produce phosphates and accumulate calcium phosphate salts

Question 25

What type of bone is laid down after a break

Answer 25

Woven bone

Question 26

How does woven bone differ to lamellar bone

Answer 26

In lamellar bone the collagen fibres are orientated in one diffraction but in woven bone they are laid down in a haphazard fashion

Question 27

Characteristics of woven bone

Answer 27

- Not as strong as lamellar | - Eventually remodelled into lamellar bone by being broken down by osteoclasts and reformed by osteoblasts

Question 28

Osteoclasts

Answer 28

- Derived from macrophage lineage | - Several will fuse and form a single giant multinucleated cell

Question 29

What is the collection of osteoclasts and osteoblast that particiapate in bone remodelling at a particular site called

Answer 29

The basic multicellular unit (BMU)

Question 30

How is bone remodelled

Answer 30

- A number of osteoclasts congregate and begin to drill into bone forming a tunnel - A blood vessel grows into the tunnel and brings osteoblasts with it - Osteoblasts line the tunnel and begin laying down new bone - Process continues until only the Haversian canal is left

Question 31

Lines around an osteon

Answer 31

Cement lines

Question 32

What are interstitial lamellae

Answer 32

Lamellae between old osteons that are the remnants of old osteons

Question 33

Periosteum

Answer 33

- Dense connective sheath around bone | - Has two layers

Question 34

Types of ossification

Answer 34

Intramembranous and endochondral

Question 35

Intramembranous ossification

Answer 35

- Mesenchymal cells differentiate into osteoblast and begin to synthesis and secrete osteoid - This process begins at the centres of ossification

Question 36

How does endochondral ossification begin

Answer 36

With a hyaline cartilage model of the bone to be formed

Question 37

Examples of bones produced from endochondral ossification

Answer 37

Most long bones, base of skull, and the medial and lateral ends of the clavicle

Question 38

Characteristics of bone

Answer 38

- Rigid - Non-permeable - Appositional growth - Cells within bone nourished by blood vessels that pervade the matrix