Cartilage and Bone Flashcards
What is cartilage and bone?
Skeletal connective tissues
What are the functions of bone?
- Structural support
- Protection
- Locomotion
- Mineral reservoir
- Blood cell production
What are the functions of cartilage?
- Locomotion - smooth surface at bone ends
- Structural support
- Template for new bone formation
What are the 2 different types of bone?
- Flat bone
- Long bones
What is periosteum in bone?
Connective tissue surrounding outer surface
What is cortical bone?
Dense outer layer
What is cancellous/trabecular/spongy bone?
Inner layer of interconnected trabeculae
What is red/yellow bone marrow?
Haematopoiesis and energy storage
What is endosteum in bone?
Inner membrane, separates bone from marrow
What is haematopoiesis?
The growth and maturation of the blood cells and other formed blood elements in the bone marrow
What are osteoblasts?
Synthesise and secrete bone tissue
What are osteocytes?
Maintain mineralised bone tissue
What are osteoclasts?
Resorbs bone
What is an osteogenic/osteoprogenitor cell?
- Bone cell precursor
- Gives rise to osteoblasts
What is the process of mineralisation of bone (deposition of hydroxyapatite)?
- Osteoblasts secrete collagen and matrix vesicles
- Matrix vesicles direct the deposition of hydroxyapatite crystals
- Hydroxyapatite crystals continue to be deposited and coalesce leading to confluent mineralisation
What structural units is cortical bone composed of?
Osteon
What is an osteon composed of?
Layers of lamellae
What does the central canal of an osteon contain?
Nerves, capillaries and lymphatics
What is the process of osteon development?
- Osteoclasts resorb a wide channel
- Nerves, capillaries and lymphatics grow into the canal
- Osteoblasts line the channel and lay down osteoid
- As osteoid is mineralised, osteoblasts get trapped as osteocytes in lacunae (tiny spaces)
- Concentric lamellae (circular layers of bone)
- Interstitial lamellae
- Circumferential lamellae (around the outside of bone)
What are the 2 layers of periosteum?
- Outer layer of dense, irregular fibrous tissue
* contains blood, lymph and nerves - Inner cellular layer adjacent to bone surface
* osteogenic cells
* osteoblasts
What is the function of periosteum?
- Site of bone synthesis
- Give rise to circumferential lamellae
What is the structure of trabecular bone?
- Contains lamellar bone - osteocytes housed in lacunae
- Lattice-like network of rods called trabeculae
- Orientated to provide maximum strength for minimum mass
- Spaces between trabeculae occupied by red and yellow marrow
- Lined externally by endosteum
What does bone remodelling occur in response to?
Growth and changing mechanical stresses upon the skeleton
What external factors is bone remodelling influenced by?
- Hormonal: calcium homeostasis
- Neuronal
- Immunological
What are the 3 types of cartilage?
- Hyaline cartilage
- Fibrocartilage
- Elastic cartilage
What can cartilage be described as and what does it provide to the body?
- It is an avascular flexible connective tissue
- Provides strength and cushioning
What is a chondroblast?
- Cells that synthesise and secrete ECM of cartilage
- Can divide to form small clusters of mature chondrocytes
Where are chondroblasts found?
Become trapped in lacunae, within cartilaginous chondrocytes
What are chondrocytes?
- Mature cartilage cells
- Maintain the integrity of cartilage
As there are no blood vessels in cartilage, how do cells receive their nutrients?
- By diffusion of metabolites through the cartilaginous matrix
Where is hyaline cartilage found?
- Nasal septum, larynx, tracheal rings and most articular surfaces
What is the ground substance like in hyaline cartilage?
- Gel-like
- Provides a smooth, firm and slightly flexible surface as it contains some fibre
What are the properties of perichondrium and what can this lead to?
- No capacity to repair following damage
- Wear and tear can eventually lead to arthritis
Which type of hyaline cartilage does not contain any perichondrium?
Articular cartilage
Where is fibrocartilage found?
- In vertebral discs and as a component of joint capsule
What property does abundant collagen fibres provide?
Strength
Where is elastic cartilage found?
- External ear, epiglottis and larynx
What does abundant elastic fibres in elastic cartilage provide?
Flexibility
What are elastic fibres synthesised by?
Chondrocytes
In what 2 ways can a fracture of bone and cartilage occur?
- Due to trauma
- Due to pathologically weakened bone
What is Osteomalacia?
- Failure of osteoid to mineralise adequately
- Bones become weakened and are prone to fracture
What is Osteomalacia associated with?
- Lack of calcium and/or phosphate
- Lack of vitamin D
- Associated with dental abnormalities
- Adults: weak jaw –> loss of teeth
- Children: Severe forms of enamel disruption
What is osteoarthritis?
- Degenerative disease of synovial joints
- Cartilage eroded sue to wear and tear
- Bone ends in direct contract
What is rheumatoid arthritis?
- Destructive auto-immune disease of synovial joints
- Immune cell infiltration
- Cartilage destroyed and replaced by fibrous tissue
- Immune mediated uncoupling of bone remodelling
- Increased osteoclastogenesis (bone resorption)
What is periodontitis?
- Destructive inflammatory disease
- Chronic immune response to oral bacteria leads to destruction of host tissues
- Immune mediated uncoupling of bone remodelling
- Increased osteoclastogenesis (bone resorption)
- Destruction of alveolar bone and subsequent tooth loss
