✅Bone Tissue Flashcards
What are the 5 functions of the skeletal system?
• Support
• Storage of minerals and lipids
• Blood cell production (Haemopoiesis)
• Protection
• Leverage
What is the percentage of calcium composition in bone?
39%
What is bone?
Bone is a connective tissue
What are the 5 stages of bone formation?
- Development of Cartilage model
- Growth of Cartilage
- Development of primary ossification centre
- Development of primary ossification centre in Epiphysis
- formation of articular Cartilage and epiphysis plate
What are the 3 key points of bone growth?
Lengthening of bones at epiphyseal plate
– Grows from cartilage
• Forms epiphyseal line when growing is complete
• Undergoing constant remodeling
– Adaptation to stress
– Healing
What are the two types of bone?
Dense or Compact or Cortical bone (85%)
Spongy or Cancellous or Trabecular bone (15%)
What are Spongy or Cancellous or Trabecular bone made of?
Traberculae
What are Dense or Compact or Cortical bone made of?
– Osteon (Haversian System)
– Central (Haversian) canal
– Lamellae
– Lacunae with osteocytes
– Canaliculi
Describe the outer layer of The periosteum
dense, irregular network of nerves and blood vessels
Describe the inner layer of the periosteum
– Osteoblasts
– Anchored to bone by collagen fibres that penetrate into bone
What are the three routes that blood uses to reach the bone tissue?
Haversian Canals
Volkmann’s Canals
Primary blood vessels
What are haversian canals?
Minute channels that lie parallel to axis of bone
What do volkmann’s canals do?
Connect the Haversian canals
What does the body have 1-2kg of (99% in bone)?
Calcium
Where do calcium ions play and important role?
Physiological process
What happens if calcium concentration increases by 30%?
Neurons and muscle cells become unresponsive
What happens if calcium concentration decreases by 35%
Convulsions
What happens if calcium concentration is reduced by 50%?
Death
What are the two types of calcium homeostasis?
Parathyroid Hormone (PTH) Calcitonin
When is PTH released into the body?
When calcium ion in blood drops
What 3 things does PTH do when released into the body?
• Stimulates osteoclast activity and enhancing of mineral recycling by osteocytes
• Increasing the rate of intestinal absorption of calcium ions by enhancing the action of calcitriol
• Decreasing the rate of excretion of calcium ions at the kidneys
What does calcitonin do when released into the body?
• Inhibits osteoclast activity
• Increase the rate of excretion of calcium ions at the kidneys
What are the 8 types of bone disorders?
Nutritional Genetic Cancer Endocrine Ageing Trauma Infection Neuromuscular
What happens to X-rays as they pass through the body?
they are partially absorbed; the denser the tissue, the greater the fraction of radiation that is absorbed
What is attenuation?
the reduction in intensity due to absorption and scattering.
What does the degree of attenuation depend on?
the tissue’s local density & composition (bones attenuate strongly, fat attenuates much less).
What does each tissue type have?
Characteristic radiodensity
What is Dual-energy X-ray Absorptiometry (DXA) the clinical system for?
diagnosing osteopenia/osteoporosis
What can DXA do?
Can measure body composition
What are the 4 key points of osteopenia?
• Inadequate ossification
• Prevalence & severity typically increase with age
• Typically starts between 30-40 years of age
• Epiphyses, vertebrae, jaws are most affected
What are the 4 key points of osteoporosis?
• Reduction in bone mass sufficient to compromise bone function
• Hormonal effects, over age 45→ 29% women & 18% men
• Effects of (in)activity
• Typically lead to fracture → independence loss → immobility
What are the 2 types of fractures?
• Closed / simple
• Open / compound
What forms rather than lamellar bone in the initial phases of fracture healing?
Formation of callus of woven (rather than lamellar) bone in the initial phases of fracture healing.
What are the 4 steps of fracture healing?
• Step 1 – Fracture Haematoma
• Step 2 – Callus Formation
• Step 3 – Ossification
• Step 4 – Remodelling
What happens at step one of the fracture healing process?
Immediately after the fracture, extensive bleeding occurs. Over a period of several hours, a large blood clot, or fracture hepatoma, develops.
What happens at stage 2 of the fracture healing process?
An internal callus forms as a network of spongy bone unites the inner surfaces, and an external callus of Cartilage and bone stabilises the outer edges.
What happens at step 3 of the fracture healing process?
The cartilage of the external callus has been replaced by bone, and struts of spongy bone now unite the broken ends. Fragments of dead bone and the areas of bone closest to the break have been removed and replaced.
What happens at step 4 of the fracture healing process?
A swelling initially marks the location of the fracture. Over time, this region will be remodelled, and little evidence of the fracture will remain.
