MSK histology Flashcards
What cells are found in cartilage?
Chondrocytes
What are immature chondrocytes called?
Chondroblasts
Where in the cartilage are chondrocytes found?
Within a space in the extracellular matrix, called a lacuna
What is the function of a chondrocyte?
Secretion and maintenance of extra-cellular matrix
What is the makeup of extra-cellular matrix of cartilage?
75% water
15% Type II collagen
10% Proteoglycan aggregates
How does type II collagen differ from type I (Found in tendons)?
It is finer and forms a 3D meshwork instead of linear bundles
What makes up the proteoglycan aggregates found in the extracellular matrix?
GAGS (Keratan sulfate and chondroitin sulfate) bound to a core protein and linked to hyaluronan
Describe the histology of hyaline cartilage
The chondrocytes are flat near the perichondreum and rounded in deeper tissue, often in pair forming cell nests (Isogenous cell groups)
What type of cartilage is shown here?
Hyaline cartilage
Describe the histology of elastic cartilage
Elastic cartilage contains typical chondrocytes
Its matrix is pervaded by yellow elastic fibres, except around the lacunae
Its elastic fibres are irregularly contoured and show no periodic banding
What are some special features of elastic cartilage?
Elastic cartilage is resistant to degradation and can regenerate to a limited degree following traumatic injury
What type of cartilage is shown here?
Elastic cartilage
Describe the histology of fibrocartilage
Fibrocartilage is dense and fasiculated, containing chondrocytes either singly or in isogenous groups, arranged into long rows, separated by coarse collagen type I fibres
It usually contains fibroblasts
The cells are ovoid and surrounded by concentrically striated matrix
What are the 4 main components of bone?
- Bioapatite (65%)
- Collagen (23%)
- Water (10%)
- Non-collagen protein (2%)
What is bioapatite?
Bioapatite is a form of calcium phosphate, mostly in the form of hydroxyapatite
What are the 2 types of bone?
- Cortical bone - outer shell - makes up diaphysis
- Trabecular bone - Inner meshwork - Makes up epiphysis
What are the main structural units of bone?
Osteons
What are osteons?
Circular rings of interstitial lamellae, which surround a Haversian canal, containing an osteonal artery and nerve
What forms the interstitial lamellae of bone?
Collagen fibres
What are the connecting canal s between Haversian canals called?
Volkmann’s cannals
What types of cells are found within bone?
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
What is the function of osteoprogenitor cells?
Osteoprogenitor cells are located on the bony surface and serve as a pool of reserve osteoblasts
What are osteoblasts?
Osteoblasts are bone forming cells which are found on the surface of developing bone, containing many RER and mitochondria
What is the function of osteoblasts?
They secrete collagen, GAGs and other components of the matrix, which is collectively known as osteoid, which becomes mineralised over time
Where are osteocytes found?
Trapped within the bone matrix
What are osteoclasts?
Osteoclasts are large multinucleate cells which are responsible for bone resorption
What is osteoid?
A mixture of collagen, GAGs and other matrix compounds which mineralise to form bone
