Bones

Question 1

What is the long bone made up of?

Answer 1

epiphysis
diaphysis
periosteum
metaphysis

Question 2

What is the epiphysis?

Answer 2

The articular head of the long bone

Question 3

What is the diaphysis?

Answer 3

The shaft. A hollow cylinder containing bone marrow in the marrow cavity where red blood cells are produced. Made up of compact bone

Question 4

What is the periosteum?

Answer 4

Fibrous connective tissue which envelopes external surfaces

Question 5

What cells are found in the periosteum?

Answer 5

Fibroblasts, mesenchymal cells and osteoclasts

Question 6

What is the metaphysis?

Answer 6

Found between epiphysis and diaphysis, region of growth in childhood

Question 7

What are the 2 types of bone?

Answer 7

Trabecular/cancellous and compact/cortical bone

Question 8

Structures found in cortical/compact bone

Answer 8

Haversian canals which carry blood along the long axis, Volkman’s canals carry blood perpendicularly, cells structured in concentric circles, each layer contains collagen fibres which have a high degree of orientation, calcium hydroxyapitite present for strength and solidity

Question 9

Properties of trabecullar/cancellous bone

Answer 9

Fewer lamellular layers so weaker bones but more flexible. Site of haemopoeisis in bone marrow

Question 10

Explain the process of trabecullar bone remodelling

Answer 10

1. Quiescence (dormancy)
2. Resorption by osteoclasts (when triggered to do so)
3. Reversal: surface exposed to osteoprogenitor cells- osteoblasts differentiate
4. Formation: osteoblasts lay down new bone

Question 11

Explain the process of compact bone remodelling

Answer 11

Osteoclasts resorb bone (acts as a cutting cone) and then osteoblasts lay down new matrix become enclosed and mature into osteocytes (acts as a closing cone)

Question 12

What is Wolff’s law?

Answer 12

Bones grow and remodel in response to the load with which it is placed with

Question 13

Explain the process of bone growth from fetus to adult

Answer 13

The cartilage model is formed by chondroblasts and reshaped by chondrocytes. Cartilage is replaced by bone by ossification. Bone growth begins in the diaphysis during fetal life

Question 14

Explain the process of after-birth endochondral ossification

Answer 14

The secondary centre of ossification is located in the epiphysis. Ends of the bond separate from the diaphysis by plates of hyaline cartilage which forms the epiphyseal plate. In this, columns of cartilage cells undergo cell division, are removed by osteoclasts and the space is invaded by osteoblasts which lay down the bone. Growth begins at the epiphyseal side and moves towards the diaphysis, growth ceases when the structures connect.

Question 15

What causes the growth of bones to stop?

Answer 15

Production of sex steriods causes the epiphyseal plates to close by process of synostosis

Question 16

Describe the different zones in after-birth endochondral ossification

Answer 16

resting zone: chondroblasts put down cartilage model at epiphyseal plate
proliferating zone: chondroblasts undergo cell division increasing in number
hypertrophic/maturation zone: chondroblasts become buried and mature into chondrocytes swelling and increasing the cytoplasm which causes the matrix to calcify
ossification zone: disorganised bone from calcification zone becomes remodelled

Question 17

Healing time for fracture?

Answer 17

Dependent on cells in local periosteum, between 2-4 weeks depending on the location of the fracture, the severity and the age of the individual

Question 18

What happens when a fracture occurs in the body?

Answer 18

Inflammation and additional blood flow causes the osteoblasts to form woven bone rapidly to bridge the gap. It is weak as the collagen fibres are irregular. Lamellar bone is laid down, presence of collagen in organised layers give strength

Question 19

What is a fibroblast?

Answer 19

A cell which forms collagen and other fibres

Question 20

What are osteoprogenitor cells?

Answer 20

Stem cells which give rise to osteoblasts

Question 21

What hormones control the equilibrium between osteoclasts and osteoblasts?

Answer 21

Calcitonin: decreases activity of osteoclasts 
parathyroid hormone (PTH): increases activity of osteoclasts

Question 22

What is Rickets caused by?

Answer 22

Vitamin D deficiency due to failure of calcium ions

Question 23

What is Scurvy caused by?

Answer 23

Vitamin C deficiency due to lack of collagen

Question 24

Explain how the equilibrium between osteoblasts and osteoclasts is controlled?

Answer 24

Controlled by signalling between different cells in the bone and actions of hormones:
calcitonin decreases osteoclast activity and decreases calcium ion levels
parathyroid hormone increases osteoclast activity and releases calcium ions