Cartilage Flashcards
Main types of collagen
Type I, II, III and IV
Type I collagen
Most abundant, widely distributed
Type II collagen
- Hyaline and elastic cartilage
- Fibres thinner than type I
Type III collagen
Reticular fibres
Type IV collagen
- Found in the basal lamina
- Does not form fibrils
What type of collagen is found in dense regular and irregular connective tissue
Type I
Where is the basal lamina
Between the epithelia and underlying supporting connective tissue
What is the function of the basal lamina
A selective barrier to the passage of materials between the epithelium and supporting tissue
What is the basal lamina involved in the control of
Epithelia growth and differentiation
What is the basal lamina composed of
GAGs, type IV collagen and glycoproteins
What other disaccharide polymer are many proteoglycans non convalently linked to
Hyaluronan
What stabilises the interaction between proteoglycans and hyaluronan
Link proteins
Describe cartilage
- Semi-rigid connective tissue
- Consists of scattered cells surrounded by amorphous appearing extracellular matrix
Composition of extracellular matrix of cartilage
Contains type II collagen which provides mechanical stability and GAGs which resist deformation by compression
Cartilage formation
- Differentiation of primitive stellate mesenchymal cells into chondroblasts
- These cells proliferate and aggregates of cells grow and begin to synthesis ground substance and fibrous extracellular material
- Cells mature into chondryocytes and these maintain integrity of cells
How dos cartilage get its nutrition
Through diffusion of metabolites
What are the cells found within cartilage called
Chrondrocytes
Characteristics of chondrocytes
- Live in the lacuna
- Vary in shape
- Flattened near the edge of cartilage
- Rounded near the centre
- Secrete and maintain extracellular matrix
What happens if vascular supply around cartilage is disrupted
The cells die, blood vessels invade the matrix and the matrix is phagocytosed and replaced by scar tissue
Composition of EMC
75% water and 25% organic materials
What is the organic material made from
60% type II collagen and 40% proteoglycan aggregates
Important glycoprotein in the cartilage matrix
Chondronectin
Function of chondronectin
Promotes the adherence of chondrocytes to the matrix of collagen
The matrix in the area around the chondrocyes is
Particularly high in proteoglycans and is known as the territorial matrix
Matrix at a distance from chundrocytes
Has fewer proteoglycans and is known as the interterritorial matrix
Connective tissue that surrounds the cartilage
Perichondrium
Layers of the perichondrium
Outer fibrous layer of dense connective tissue and an inner chondrogenic layer which provides now chondroblasts to the adjacnt cartilage
What does the perichondrium contain
Blood vessels that supply nutrients to the whole of the avascular cartilage
How does cartilage grow
Appositional growth at the edge and interstital growth with the matrix
What are the types of cartilage
Hyaline cartilage, elastic cartilage and fibrocartilage
Hyaline cartilage
Blue-white in colour and translucent. Most common form
Elastic cartilage
Light yellow in colour. Addition of elastic fibres makes it flexible
Fibrocartilage
White in colour. Hybrid between the other two. Has bands of densely packed type I collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilaginous ECM
Where is hyaline cartilage found
Articular surfaces, tracheal rings, costal cartilage, epiphyseal growth plates and the precursor to bone in the foetus
What type of cartilage is found at a synovial joint
Hyaline cartilage
Where is elastic cartilage found
Pinna of the ear, epiglottis and auditory tube
Where is fibrocartilage found
Intervertebral discs, where the tendon inserts into the bone (enthesis) and pubic symphysis
What effect does age have on cartilage
Chondrocytes from older animal produce shorter proteoglycans which may lead to lessened ability to attract water molecules and decreased resistance to compression = damage of articular cartilage and osteoarthritis
Characteristics of cartilage
- Deformable
- Permeable
- Appositional and interstitial growth
- Cells in the matrix nourished through diffusion
