Cartilage And Bone Flashcards
What category of tissues does cartilage and bone fall under
Connective tissue
Skeletal connective tissues
Cartilage and bone are both modified rigid forms of connective tissue
Functions of the skeletal system
Support
Storage of mineral and lipids like phosphate and calcium ions
Blood cell production in the red bone marrow
Protection
Types of bone cells
Osteoclasts
Osteogenic cells
Osteocytes
Osteoblast
Osteoclasts are derived from what family?
Phagocytes
Classify the skeletal connective tissues
Bones (axial and appendicular)
Cartilage ( hyaline Fibrocartilage elastic)
What is the difference between cartilage and bone
Cartilage is flexible and semi rigid, can withstand compressions forces and also bend slightly
while bone is rigid, because ECM is calcified
Components of all cartilage
Cells (chondroblasts , Chondrocytes )
ECM (fibres and ground substance)
Fibres include collagen and elastin
Ground substance is called chondroitin sulphate also called aggrecan
Why can’t cartilage become thick
Avascular
What is the appearance of the ECM of cartilage
Firm glassy solid gel
What are the differences between ECM in cartilage vs connective tissue proper?
In cartilage, firm solid glassy gel
In connective tissue, water, jelly-like
Location of Chondrocytes
Lacunae
What is the name of the dense irregular connective tissue surround the cartilage
Perichondrium
Function of Perichondrium
Mechanical support and protection
Attached the cartilage to other structures
3 types of cartilage
Hyaline
Elastic
Fibrocartilage
What is the other type of cartilage that falls under hyaline cartilage and where is it found.
Articular cartilage found at joints, doesn’t have Perichondrium
What fibre is found in hyaline cartilage?
Type 2 collagen
What are the characteristics of Fibrocartilage
No Perichondrium
Strongest durable tough
Dense irregular Collagen fibres
Chondrocytes arranged in rows
What are the characteristic of elastic cartilage
Elastic fibres
Flexible
ECM Similar to hyaline
Found at the ear/ epiglottis
Using van gieson stain, can see a lot of black elastic fibres
2 ways in which cartilage grow
Interstitial and appositional
What is cartilage for?
- to form the supporting framework of some organs, such as the walls of airways (nose, trachea, larynx and bronchi), where it prevents airway collapse.
- to form the articulating surfaces of bones, and
- to form the template for the growth and development of long bones, and most of the rest of the fetal skeleton (gradually replaced by bone).
chondrocytes grow and divide and lay down more matrix inside the existing cartilage. This mainly happens during childhood
Interstitial growth of cartilage
new surface layers of matrix are added to the pre-existing matrix by new chondroblasts from the perichondrium.
Appositional growth of the cartilage
Histological components of bone
ECM (ground substance and fibres)
Cells
What’s the ground substance of bone
Chondroitin sulphate and hyaluronic acid
What is the fibre in bone
Type 1 collagen
What is Osteoid
Unmineralised organic component of ECM
Before the ECM is calcified, it’s Osteoid
What is most abundant component of bone
Hydroxyapatite (70%)
What cells are present in bone
Osteoclasts
Osteoblasts
Osteocytes
Osteoprogenitor
What is the formula for hydroxyapatite
Ca10(PO4)6(OH)2
How do collagen fibres and hydroxyapatite interact
Collagen offers flexibility while hydroxyapatite is brittle. Collagen lays the framework for hydroxyapatite crystals to settle in
Calcification occurs only in presence of collagen fibres - salts crystallize in the spaces between the fibres, then accumulate around them.
Bones are organs. What else is part of bone
Bone tissue
Periosteum which is Connective tissue
Adipose tissue
Blood vessels
Nervous tissue
Articular cartilage
What are the types of bone
Primary bone is woven bone
Replaced by lamellae bone
Two types of mature bone (compact/cortical and spongy/trabecular)
Which type of bone is more abundant. Cortical or trabecular?
Cortical (80%) and spongy (20%)
Where is epiphysis in bone
There is the proximal and distal epiphysis, regions at the two ends of the bone
What region is the diaphysis
The middle portion
What is the function of osteoblast
Synthesizes and secretes Osteoid
What is osteoclasts and what is it’s function
Resorts bone , derived from macrophage lineage. They are the only ones NOT derived from Osteoprogenitor stem cells
How do osteoclasts work
Monocytes in bloodstream collect at the site of resorption. They fuse to form Multinucleated osteoclasts that stick to the surface of the bone and resort .
What is the dense fibrous layer outside of bone
Periosteum. It is not found in the regions of bone covered by articulated cartilage
Endochondral
Formation of bone onto a temporary cartilage model (hyaline) or scaffold
Intramembranous
Formation of bone directly onto fibrous connective tissue, no cartilage stage
Describe the process of bone remodelling
Bone remodelling is required for growth . When there is mechanical stress, the bones release calcium. There is also hormone control of bones (PTH and calcitonin)
How is periodontitis a disorder of bone and cartilage?
Periodontitis is an inflammatory disorder.
When osteoclasts > osteoblasts, increased osteoclastogeneisis. Destruction of alveolar bone, periodontal ligament leading to tooth loss
Osteomalacia
Osteoid doesn’t mineralise enough, bone isn’t rigid. so the bone is weak. Hydroxyapatite most affected.
What’s rickets
Osteomalacia
What is the special characteristic of cancellous bone
Cancellous another name for trabecular bone
Trabecular bone does NOT have osteons
Describe the structure of spongy/cancellous/trabecular bone
No osteons
Contains lamellar bone ie bone is arranged in layers
Spaces between trabeculae occupied by marrow
Lined externally by endosteum
Describe the structure of cortical/compact bone
What is a characteristic of osteoclasts
Multinucleated
Where are Osteogenic cells found
Periosteum or Endosteum
Location of osteocytes
Within lacunae
Only one osteocytes in each lacunae
Narrow passageway between osteocytes for cell cell communication
Canaliculi
Function of osteocytes
- Maintain the protein and mineral content of matrix by dissolving the matrix and rebuilding it with new hydroxyapatite crystals
- Repair of damage bone. When released from lacunae, osteocytes can convert to a less specialised type of cell
Compact bone contains parallel osteons and spongy bone contains trabeculae
Axial bones
Head and thorso so spine, rib cage, skull
Appendicular bones
Appendages /limbs
Pelvis
Shoulders
Arms and legs
Medullary cavity
In the middle of disphysis
What is the organic and inorganic component of bone
Organic - Osteoid (ground substance and collagen fibres)
Inorganic - hydroxyapatite (crystals of calcium phosphate)
Describe the structure of an osteon
Osteon is also known as haversian system
Middle of osteon there is a central canal
Concentric lamellae
Where is circumferential lamellae located
Runs along the periosteum
Interstitial lamellae location
In between osteons
What is interstitial lamellae
As a result of the continuous resorption and redeposition of bone, complete newly formed Haversian systems are disposed between partly resorbed systems formed earlier. The remnants of lamellae no longer surrounding Haversian canals form irregular interstitial systems between intact Haversian systems.
Function of Volkmann’s canal
Connect The Central canal with the periosteum so that the bone tissue has blood supply
Also connects central canals to each other
What is the structure of trabeculae
Endosteum outside
Parallel lamella
No osteon
Osteocytes in lacunae with Canaliculi extending out
Appositional vs interstitial growth
Appositional growth occurs when chondroblasts secrete new matrix along existing surfaces and this causes the cartilage to expand and widen. In interstitial growth, chondrocytes secrete new matrix within the cartilage and this causes it to grow in length.
