PATHOLOGY- Bone Disorders Flashcards
What is bone?
Ridged inflexible mineralised connective tissue
What is bone mineralised by?
Calcium and phosphate salts
Why are bones important structurally and metabolically ?
Structural
1. Provides physical integrity/ support
2. Protects squishy organs
3. Allows for insertion of muscles and tendons
Metabolic
1. Provides minerals
2. Important in haematopoiesis
What minerals does bone provide
- Calcium
- Phosphorous
- Magnesium
What is haematopoiesis?
It is the formation, development and maturation of blood cells in adult bone marrow
Where does haematopoiesis occur in adults?
Bone marrow
Name the parts that make up bone
- Non cellular mineralised matrix
- Cells that maintain the matrix
What is the non cellular mineralised matrix that makes up bone made up of?
- Type I collagen- osteoid
- Calcium phosphate (calcium hydroxyapatite)
- Regulatory protein and growth factors
What is type 1 collagen in bone called?
Osteoid (extraceulluar matrix in bone)
List the cells that maintain the matrix in bone
- Osteoblasts
- Osteocytes
- Osteoclasts
Why is mineralisation critical?
The osteoid would be soft and bendy if it wasn’t mineralised
What do osteoblasts do?
They build up the bone
What is the origin of osteoblasts
Mesenchymal origin
What is the function of osteoblasts?
- They secrete osteoid
- Needed for mineralisation
What are osteocytes
Inactive osteoblasts that are trapped in the bone
What is the origin of osteoclasts
Macrophage lineage
What do osteoclasts do?
They are involved in bone resorption and remodelling
How can bone be categorised?
- Maturity type
- Location type
Name the different types of bone based on maturity
- Woven bone (immature bone)
- Lamellar bone
Describe woven bone
It is immature bone as the osteoid collagen is random
It is remodelled into lamellar bone
What causes the random osteoid formation in woven bones?
Rapid bone turnover by osteoblasts
What is woven bone remodelled into?
Lamellar bone
Where is woven bone found?
Fractures
Fetal developemt
Describe lamellar bone
Made up of parallel bands/ sheets of lamellae
Where is lamellar bone found?
Makes up the majority of normal healthy adult bone
What are the two different types of lamellar bone?
Compact/cortical bone
Cancellous/ trabecular bone
Which type of bone is stronger from woven and lamellar?
WHY?
Lamellar bone is much stronger due to regular arrangement of lamellae
Name the different types of bone based on location?
- Cortical/ compact
- Cancellous. trabecular
Describe Cortical bone
Forms hard outer shell and regular shape
It is highly organised
Follows the Haversian system
What system does cortical bone follow?
The Haversian system
What is the Haversian system
Columns of lamellar bone (v compact and dense)
Describe cancellous/ trabecular bone
Spongy non structural “filler” bone
What is found in the spaces between cancellous bone?
Bone marrow
How are the different bone types organised?
Cortical bone surrounds cancellous bone
Why is bone remodelling important?
- To maintain bone strength as your bones constantly suffer from trauma like micro fractures through the day
- To be able to release metabolites
List the stages of the bone remodelling cycle
- Activation
- Resorption
- Reversal
- Formation
How is bone remodelling activated?
By hormones or damage
What happens when bone remodelling is activated by hormones of damage>
- Osteoblasts are activated
- Cytokines are released
- Osteoclasts stick to the surface of the bone
What is the next stage after activation in the bone remodelling cycle
Resorption
What happens in the Resorption stage of the bone remodelling cycle
- Mono nuclear osteocytes that are stuck to the surface of bone secrete substances
- These substances reabsorb bone
- Create pits on the surface
- Mono nuclear osteocytes undergo apoptosis or migrate
What is the next stage after Resorption in the bone remodelling cycle
Reversal
What happens in the reversal stage of the bone remodelling cycle
Monocytes clear debris for bone formation
What is the last stage after reversal in the bone remodelling cycle
formation
What happens in the formation stage of the bone remodelling cycle
- Osteoblasts are recruited
- They secrete osteoid matrix and initiate mineralisation
- Osteoblasts sit on the new bone
- some undergo apoptosis and some are incorporated as osteocytes
What is another name for immature bones?
Woven bone
What is another name for mature bones
Lamellar bone
Compact and cancellous bone are both what type of bone?
Lamellar bone
What is osteoarthritis?
Progressive erosion of articular cartridge
Is osteoarthritis just erosion?
No it is a complex imbalance of damage and repairs
What happens in osteoarthritis
Cartilage is worn away and underlying bone is exposed
This leads to damage and the formation of cysts / osteophytes causing inflammation pain
This ultimately leads to narrowing joint space
What are osteophytes
Abnormal growth in bone
How common is osteoarthritis?
uptown 80% of over 65s have evidence of having osteoarthritis
but only 1/4 have symptoms
What are some of the symptoms of osteoarthritis
- Pain/ functional limitation
- Morning stiffness
What are some of the signs of osteoarthritis
- Crepitus (crunchy)
- Restricted movements
- Bony enlargement
- Instability/ muscle wasting
What are the differences between signs and symptoms
Signs are something you observe as a
clinical
Symptoms are things patients present with
What is a primary cause for disease?
Unknown cause or unknown origin for a disease
no underlying cause for the disease
Give some secondary causes of osteoarthritis
- Pre existing joint damage
- Metabolic disease
- Systemic disease
How do you investigate osteoarthritis
- Blood tests to make sure rheumatoid factor is negative and to look for bone markers
- X-ray will show cartilage loss, joint space narrowing and cysts
What would a raised rheumatoid factor suggests?
the patient may have rheumatoid arthritis
How do we manage osteoarthritis
- Physical: weight loss, hydrotherapy
- Medications: NSAIDS, steroids
- Surgery: joint replacement
What is rheumatoid arthritis?
It is an autoimmune disease consisting of persistent inflammation (synovitis) leading to chronic symmetrical
List the 3 factors that strongly influences the progression of rheumatoid arthritis
- Gender: women at higher risk
- Genetic: associated with human leucocyte antigen (HLA)
- Environmental: periodontal disease may contribute to it
Who is most affected by rheumatoid arthritis?
Younger (30-50)
x3 more women
rarer 1%
What does synovitis
Inflammation
What happens in rheumatoid arthritis
Citrullination of self antigens leading to loss of normal tolerance as the antigens are no longer recognised as self cells
Auto immune response occurs leading to inflammation leading to damage