Bone; Structure, Growth and Repair

Question 1

What is compact bone?

Answer 1

Dense bone on the cortex (Outside)

• Contains osteons
• Covered in periostium

Question 2

What is spongy bone?

• Also known as trabecular, cancellous bone.

Answer 2

• Internal to compact bone
• Distributes loads
• Reduces bone weight

Question 3

What is periosteum?

Answer 3

• Outer layer of bone
• In the mature adult it can be divided into;
• Fibrous outer layer
• Internal layer of osteoprogenitor cells

Question 4

What is endosteum?

Answer 4

• Internal lining of cell surfaces

- Contains osteoblasts and osteoprogenitor cells

Question 5

What is bone marrow?

Answer 5

Red;
- Heamopoesis; RBC made and stored

Yellow
- Fat storage

Question 6

Is adipose found in the bone?

Answer 6

Yes, adipocytes are found in bone

Question 7

What are lammellae?

Answer 7

Concentric layers of bone that form a unit (Osteon) in compact bone

Question 8

What are osteons?

Answer 8

Unit of compact bone that contains its own blood supply.

Contain the lamallae of the bone

Question 9

What are canaliculi?

Answer 9

Haversion cannels?

Little canals - osteocytes project through and connect with each other.

Involved in nutrition and communication

Question 10

Whats the epiphysis?

Answer 10

Head of the bone.

Can be covered in articular cartilage.

Generally contains spongy bone

Question 11

Whats the metaphysis?

Answer 11

Region where the epiphyseal growth plate is located.

In mature adults epiphyseal lines develop

Question 12

What is the diaphysis?

Answer 12

Shaft of the bone. Contains a medullary cavity in long bones with nutrient vessels.

Question 13

What are osteoprogenitor cells?

Answer 13

Mesodermal-Mesenchyme in origin. Develop into osteoblasts.

Question 14

What are osteoblasts?

Answer 14

Secrete ostoid (bone ECM) once surrounded by ECM they differentiate into osteocytes

Question 15

What are osteocytes?

Answer 15

Osteocytes maintains bone tissues

Question 16

What are osteoclasts?

Answer 16

Osteoclasts breakdown the ECM of bone. Bone reabsorption.

Derived from macrophage/monocyte lineage.

Question 17

Describe the ECM of bone;

Answer 17

Water
Collagen (30%, tensile strength)

Inorganic minerals; Hydroxyapetite (CaPO4, CaOH2)

Question 18

What sort of forces does the lamellae structure of compact bone resist against?

Answer 18

Compression, tensile and torsion stresses.

Question 19

Describe the type of lamellae in compact bone;

Answer 19

Concentric lamellae (Osteons)
Outer circumferential lamellae
Interstitial lamellae

Question 20

Are lamellae found in spongy bone?

Answer 20

Yes, theyre irregular giving the trabecular structure.

Question 21

How do osteocytes in spongy bone gain their nutrition?

Answer 21

Diffusion from the morrow that surrounds them

Question 22

What are the two types of bone formation in growth and development (not fracture)?

Answer 22

Endochondral ossification

Intramembranous ossifcation

Question 23

Describe intramembranous ossification;

Answer 23

Osteoprogenitor cells condense to form a primary ossification center in the mesenchyme.

Ostoid is deposited and a trabecular network is formed

The bone organises itself to form a compact outer shel with periosteium derived from the surrounding mesenchyme.

Question 24

Describe endochondral ossification;

Answer 24

In the developing fetus;

1) Mesenchyme cells develop into chondrocytes.
2) Chondrocytes produce a cartilage model.
3) Primary ossification centre develops in the diaphysis region. With nutrient and blood vessels invading. Osteoclasts core out medullary cavity.
4) Secondary ossification centre develops at the epiphysis.
5) Articular and hyaline cartilage develop.

Gradients of growth factors direct chondrocytes, hypertrophies chondrocytes and deposits bone.

Question 25

How do bones grow longer and wider?

Answer 25

Longer = Endochondral ossifcation
Wider = Appositional growth (ostoid is deposited on the outside, interal bone is consumed)