Bone 1

Question 1

Name 4 main functions of Bone:

Answer 1

• A mineral store (in case of malnutrition)
• Protection
• Weight bearing/support
• Blood Formation (red bone marrow)

Question 2

Explain the structure of Osteon/Haversian systems in compact (cortical) bone:

Answer 2

Organised into circular structures called osteons which surround haversian channels that carry blood vessels (giving the name Osteon/haversian systems).

Question 3

Explain the structure of Spongy Bone:

Answer 3

A network of lamellated trabeculae (partitions formed by connective tissue) filled with marrow.
The trabeculae are orientated in the direction of the main mechanial forces acting on the bone.

Question 4

What are 3 other names for spongy bone?

Answer 4

Cancellous, tabecular and diploe bone.

Question 5

What are Volkmanns channels?

Answer 5

Horizontal Volkmanns channels carry blood vessels and link haversian channels in compact bone.

Question 6

What are osteons made of?

Answer 6

Osteons are made of osteocytes and concentric sheets of bone matrix (lamellae).

Question 7

What are the 6 main bone types?

Answer 7

• Flat Bone
• Short Bone (carpal in hand)
• Long bone (femur)
• Sutural Bone
• Irregulalar Bone (Vertebre)
• Sesamoid Bone (Patella)

Question 8

Name two types of Bone Development?

Answer 8

• Endochondral, the most common type

- Intramembranous, flat bones e.g. flat bones of skull, mandible and clavicle.

Question 9

What are the 4 steps of endochondral bone development (ossification)?

Answer 9

• A cartilage model of the bone is formed
• Blood vessels invade and vascularize the cartilage
• Bone replaces the cartilage (ossification)
• Cartilage remains in the epithyseal growth plate but eventually ossifies too.

Question 10

How does intramembranous bone development (ossification) occur?

Answer 10

• Mesenchymal (multipotent stem cells) cells develop into osteoprogenitor cells.
• osteoprogenitor cells mature into osteoblasts and start depositing bone
• Residual mesenchymal cells develop into blood vessels and marrow

Question 11

What are the 2 main differeneces between endochondral and intramembranous ossification?

Answer 11

• intramembranous involves no cartaligenous phase

- intramembranous can occur in adult cortical (compact) bone

Question 12

What 3 cell types make up Bone and what are their functions in short?

Answer 12

• Osteoblasts, secretes bone tissue
• Osteocytes, formed when an osteoblast becomes embedded in the bone it secretes. They maintain the bone matrix and sense mechanical forces.
• Osteoclasts, large & multinucleic. It absorbs bone tissue during growth and healing.`

Question 13

What makes up the ECM of bone tissue?

Answer 13

• the largest part is hydroxyapatite crystals (mineral)
• Type 1 collagen
• a lower than normal amount of water

Question 14

What is the function of hydroxyapatite in the ECM?

Answer 14

• It makes the bone very stiff and able to support other structures
• It is very strong under compressio
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Question 15

What is the function of type 1 collagen in the ECM?

Answer 15

• It give the bone flexibility and reduces fracture risk

- its very strong under tension

Question 16

What does “dynamic bone” refer to?

Answer 16

Bone is dynamic because it has a constant turnover of cells being removed and formed resulting in a completely new skeleton every 10 years.
This makes it very good at fracture healing and also allows mechanical adaptations such as the increased thickness of bone in the legs of runners.

Question 17

What is the origin & function of an osteoblast?

Answer 17

An immature cell prodcued from osteoprogenitor cells in the periosteum and endosteum
Produces bone matrix and initiates calcification

Question 18

What is the origin and function of an osteocyte?

Answer 18

Mature bone cells found inside a lancuna ( a small pit) and communicates with close and distant cells/tissues through small channels called caniliculi.

They develop from osteoblasts that have become trapped in the bone matrix.

They maintain the bone matrix and are involved in sensing mechanical forces.

Question 19

What is the origin and location of an osteoclast?

Answer 19

Osteoclasts are multinucleic cells derived from monocytes and macrophages.
They are found on the bone surface in Howship’s lacunae (resorbtion pits)

Question 20

What is the shape and function of an osteoclast?

Answer 20

Osteoclasts are large cells with a “ruffled border”.

They resorb bone matrix.

Question 21

What 3 things make up the ECM in bone tissue?

Answer 21

Minerals (hydroxyapatite), water and Type 1 collagen

Question 22

Describe 3 properties of the modified Type 1 collagen fibres in the bone ECM:

Answer 22

• Theyre strongly crosslinked
• They have large “gaps” between fibres to allow space for hydroxyapatite crystals
• Their orientation is linked to mechanical forces acting on the bone.

Question 23

Name and shortly describe the cause of 3 disorders of remodelling:

Answer 23

• Osteoporosis. Resorbtion has a greater rate than formation
• Paget’s Disease: The rates of resorbtion and formation are both above normal. End up with very weak bone.
• Osteopetrosis: The rate of resorbtion decreases but formation stays normal. End up with abnoramlly brittle and dense bones

Question 24

At what age (roughly) is the average peak bone mass?

Answer 24

Mid-20s

Question 25

What variables effect bone mass?

Answer 25

• genes
• enviroment. e.g. smoking, calcium intake, exercise
• Weightlessness or bed rest (decreases bone mass)

Question 26

How does exercise affect bone mass?

Answer 26

Athletes, particularly those in high impact sports (basketball, running etc), have a higher bone mineral density (BMD) than normal people. A response of the body to increased mechanical loads and forces.

Question 27

Name two membranes in the bone and their locations:

Answer 27

The periosteum wraps around the bone except at surfaces of joint
The endosteum lines the medullary cavity in long bones.