Bone Function and Repair Flashcards
Name the three categories of bone function
- Mechanical
- Synthetic (Haemopoiesis)
- Metabolic (Fat/Mineral Storage)
What are the two types of Ossification?
Endochondral - Formation of long bone from cartilage template
Intracellular-Membranous - Formation of bone by clusters of Mesenchymal Stem Cells in centre of the bone
Describe the 3 stages of Intracellular-Membranous Ossification
- Mesenchymal stem cells aggregate and differentiate into Osteoblasts
- Ossification occurs and bone spicules spread and interconnect
- Blood vessels get trapped and form Cancellous bone
What does Intracellular-Membranous Ossification produce?
Immature bone that can be remodelled into mature bone
Describe the 3 stages of Intra-Membranous Ossification of Flat Bone
- Mesenchymal Stem Cells > Osteoprogenitor Cells > Osteoblasts
- Osteoblasts lay down an Osteoid which mineralises into bone tissue Spicules
- Spicules join to form Trabeculae and Lamellae of mature Corticol bone
What is Appositional Growth?
Growth accomplished by the addition of new layers to those previously formed
Describe Appositional Growth in Cartilage in terms of Chondrocytes
- Chondrocytes separate and enlarge
- Calcified Cartilage is replaced by bone
- Bone is added to Diaphysis
What increases and what stays the same in Appositional Growth?
- Length of bone increases
- Epiphyseal plate remains unchanged
What stages occur in Appositional bone growth?
- Extracellular matrix is ossified
- Osteoblasts add bone by Appositional Growth
- Osteoclasts degrade bone round edges
What are the fundamental functional units of compact bone called?
Osteons
What 4 structures compose an Osteon and what is their purpose?
Osteocytes - Bone forming cells joined by long projections
Haversian/Volkmann’s Canals - Carry arteries, veins, lymph vessels and nerves
Reabsorption Canal - Starting point for remodelling
What is the difference in Osteocyte arrangement between immature and mature bone?
Immature - Random arrangement
Mature - Arranged in concentric lamellae of osteons
Does Cancellous bone contain blood vessels?
No as it is surrounded by red bone marrow and has spaces which contain bone marrow
What 2 structural features contribute to bone strength?
- Lamellae that can slip past each other to resist force
- Osteons remodel themselves to thicken bone
What are the 4 bone stability factors?
- Osteocyte Activity
- Osteoblast Activity
- Osteoclast Activity
- Nutrition
Name 3 hormones that influence bone stability
- Oestrogen
- Testosterone
- Parathyroid Hormone
- Calcitonin
Name 3 vitamins that contribute to bone strength
Vitamin A
Vitamin D3 - aids calcium absorption
Vitamin C - aids collagen synthesis
Vitamin K/B12 - role in bone protein synthesis
State the 7 steps of bone repair
- Haematoma formation
- Tissue Death
- Inflammation and Cellular Proliferation - Neutrophils/Osteoclasts
- Formation of Granular Tissue - New blood vessels develop
- Fibrocartilagenous Callus Formation - Collagen and Hyaline cartilage
- Consolidation Callus Formation - Ossification to Cancellous bone
- Bone Remodelling - Cancellous Bone > Compact Bone
What are the two processes in Bone Remodelling called?
- Cutting Cone
- Closing Cone
What happens in the stages of cutting and closing cone?
Cutting Cone - Osteoclasts make a wide tunnel in the bone
Closing Cone - Osteoblasts make a smaller tunnel of Corticol bone forming a new Osteon
What increases fracture susceptibility?
Loss of trabecular bone mass
Name 4 clinical conditions associated with bone fragility
- Osteogenesis Imperfecta
- Rickets
- Osteomalacia
- Osteoporosis
- Achondroplasia
What deficiency causes Rickets and what effect does it have?
- Vitamin D deficiency
- Results in poor calcium mobilisation and ineffective mineralisation
What is the effect of Rickets?
Soft bones which causes bowed legs
