S12) Cartilage Flashcards
What is cartilage?
Cartilage is an avascular tissue that consists of an extensive extracellular matrix in which lie chondrocytes
What are chondrocytes and what do they do?
The chondrocytes are cartilage cells which produce and maintain the extracellular matrix
What is the role of glycosaminoglycans?
GAGs permit ready diffusion of substances between the chondrocytes and the blood vessels surrounding the cartilage
Describe the structure of the extracellular matrix
The extracellular matrix is solid and firm, but also rather pliable and therefore resilient to the repeated application of pressure (hyaluronic acid assists this)
Explain how the structure of the extracellular matrix is adapted to its function
High hydration & transient movement of water in the matrix, permits resilience to varying pressure loads
Identify and distinguish between the structure of the three types of cartilage
- Hyaline cartilage: matrix containing proteoglycans, hyaluronic acid and type II collagen
- Elastic cartilage: matrix like hyaline cartilage but with many elastic fibres and elastic lamellae
- Fibrocartilage: matrix like hyaline cartilage but with abundant type I collagen fibres
Where can hyaline cartilage be found?
- Nose cartilage
- Articular cartilage of joint
- Costal cartilage
- Trachea cartilage
The only cell type in hyaline cartilage is the chondrocyte.
Describe its role and properties
- Chondrocytes are present singly or, if recently divided, as small clusters called isogenous groups
- The chondrocytes within the isogenous groups separate as they lay down extracellular matrix
Explain the role of hyaline cartilage in bone development
In early foetal development, hyaline cartilage is the precursor model of those bones which develop by endochondral ossification
What is the role of the perichondrium?
- Fibroblast-like cells of the perichondrium give rise to flat, new formed chondroblasts
- The chondroblasts secrete matrix components and round up to develop into chondrocytes
In terms of cartilage, distinguish between appositional and interstitial growth
- Appositional growth: involves an increase in width due to growth from the periphery (perichondrium)
- Interstitial growth: involves an increase in length due to the deposition of further matrix by isogenous groups deeper in the cartilage
What do chondrocytes lie in?
Each chondrocyte lies in a lacuna (pl. lacunae)
Where can elastic cartilage be found ?
- External ear (pinna)
- Epiglottis
Explain how elastic cartilage differs from that of hyaline
- The many elastic fibres confers elasticity upon the cartilage, in addition to the resilience of hyaline cartilage
- Elastic cartilage does not calcify (hyaline calcifies with age)
Where can fibrocartilage be found?
- Intervertebral discs
- Pubic symphysis
- Sternoclavicular joint
- Meniscus