lecture 4 - bone tissue

Question 1

What are the percentages of organic and inorganic components of the extracellular matrix of bone?

Answer 1

33% organic, 67% inorganic

Question 2

What is the main organic component of bone tissue?

Answer 2

Collagen

Question 3

What is the purpose of collagen in bone tissue?

Answer 3

To make it slightly flexible, preventing shattering of the bone

Question 4

How is collagen structured in bone tissue?

Answer 4

Long fibres of collagen sit in a ground substance called proteoglycans

Question 5

What is the ground substances that collagen sits in?

Answer 5

Proteoglycans

Question 6

What are the inorganic components of bones?

Answer 6

Mineral salts

Question 7

What is the main mineral salt in bone?

Answer 7

Hydroxyapatite

Question 8

What type of substance is hydroxyapatite?

Answer 8

A calcium phosphate mineral

Question 9

What is the function of the inorganic component of bone tissue?

Answer 9

Makes the bone hard and resistant to compression

Question 10

What percentage of bone mass is given by cells?

Answer 10

2%

Question 11

What are the types of bone cells? (4)

Answer 11

Osteogenic cells, Osteoblasts, Osteoclasts, Osteocytes

Question 12

What is the role of osteogenic cells?

Answer 12

They are stem cells that produce osteoblasts

Question 13

What is the function of osteoblasts?

Answer 13

They produce/build new bone matrix in a process called ossification.

Question 14

Process of bone growth?

Answer 14

Ossification

Question 15

What is the function of osteocytes?

Answer 15

They maintain the bone matrix by recycling proteins and minerals and controlling the production/destruction of bone by directing the osteoblasts and osteoclasts.

Question 16

What is the function of Osteoclasts?

Answer 16

They remove bone matrix in a process called osteolysis.

Question 17

Process of bone destruction?

Answer 17

Osteolysis

Question 18

What are the macroscopic features of compact bone?

Answer 18

Dense and inpenetrable outer surface (periosteum) with small holes/foramina for the blood supply.

Question 19

What is the outer surface of bone called?

Answer 19

Periosteum

Question 20

What is the outermost layer of compact bone tissue called?

Answer 20

Cirfumferential lamellae

Question 21

What fills the gap between osteons in the compact bone matrix?

Answer 21

Interstitial lamellae

Question 22

What is the main unit/component of compact bone?

Answer 22

Osteon

Question 23

What are the components of an osteon? (4)

Answer 23

Central canal, lamellae, lacunae, canaliculi

Question 24

What is the function of the central canal of an osteon?

Answer 24

It is a tube that contains nerves and blood vessels which carry nutrients to cells within the matrix.

Question 25

What is the structure and function of the lamellae in compact bone?

Answer 25

The lamellae form rigid rings around the central canal, and contain collagen to resist forces.

Question 26

What is the structure and function of lacunae in bone tissue?

Answer 26

They are ‘lakes’ that hold the osteocytes which maintain the bone and control its growth.

Question 27

What is the structure and function of canaliculi?

Answer 27

They are the channels that lead from the central canal, through the extracellular matrix, to the lacunae to provide the osteocytes with nutrients.

Question 28

What are the struts found in cancellous bone?

Answer 28

Trabeculae

Question 29

What is the structure of trabeculae?

Answer 29

Multidirectional struts of lamella bone.

Question 30

How does cancellous bone resist force?

Answer 30

The multidirectional trabeculae struts resist forces around a joint from several directions, before channeling down the diaphysis of a long bone or outwards through a short bone.

Question 31

What is the structure of trabeculae?

Answer 31

Made up of lamellae with Lacuna filled osteocytes. The canaculi flow straight to the trabeculae surface, without the need for a central canal as nutrients can be absorbed from within the lattice.

Question 32

How is weight force channeled in the cancellous bone of the pelvis?

Answer 32

Weight is channelled around the ilia into the femur.

Question 33

What is the term for an increase in bone diameter?

Answer 33

Appositional growth

Question 34

What is the process of appositional growth?

Answer 34

Osteoblasts add layers of circumferential lamellae to the outer layer of the bone, while osteoclasts remove bone from the medullary cavity.

Question 35

What is bone homeostasis?

Answer 35

The balance of osteoclast and osteoblast activity, so that bone mass remains constant.

Question 36

Why might the body break down bone?

Answer 36

To mobilise minerals such as calcium and phosphate

Question 37

How is bone structure ‘plastic’?

Answer 37

Remodelling allows bones to change shape to withstand repeated stress.

Question 38

What is osteopenia?

Answer 38

When bone mass decreases as Osteoclast activity exceeds osteoblast activity

Question 39

What is the diagnosis of clinically significant osteopenia?

Answer 39

Osteoporosis

Question 40

What are the symptoms of osteoporosis?

Answer 40

Compression fractures (e.g. of the vertebrae) or breaks due to the weakening of bones caused by the thinning of trabeculae in cancellous bone.

Question 41

At what age does bone mass peak?

Answer 41

25-30

Question 42

Why are women more prone to osteoporosis?

Answer 42

They lose oestrogen after menopause.

Question 43

How does excercise prevent osteoporosis?

Answer 43

it stimulates osteoblastic activity

Question 44

Where are osteogenic cells found in the bone?

Answer 44

In the inner layer of the periosteum and in the endosteum

Question 45

What is the name of the cellular layer that lines medullary cavities and blood vessel passage ways in bone?

Answer 45

Endosteum