Joints, Synovial Fluids and Cartilage Flashcards
Which joints are fibrous joints
Peridontal Ligament, the cranial sutures and the interosseous membranes
Describe a fibrous joint
At a fibrous joint, the adjacent bones are directly connected to each other by fibrous connective tissue, and thus the bones do not have a joint cavity between them
State the three types of fibrous joints
Sutures, Gomphoses and Syndesmoses
Sutures
Immovable joints only found between, the flat plate like bones of the skull
When are suture joints important
At birth
Gomphoses
Immovable joint where the teeth articulate with their sockets in the maxillae or the mandible
Syndesmosis
Movable joints in which bones are held together by an interosseus membrane
What are the function of syndesmosis joints
Provide strength along the length of long bones
Give examples of syndesmosis joints
Middle radio-ulnar and the middle tibiofibular joints
In cartilaginous joints, what are the bones attached by
Fibro or hyaline cartilage
What type of cartilage do synchondroses or primary cartilaginous joints contain
Hyaline
Give an example of a primary cartilaginous joint
Between the diaphysis and epiphysis
symphyses
Involve either hyaline or fibrocartilage and are slightly movable. An example is the pubic symphysis
Hinge synovial joint
Permits flexion and extension. Elbow joint is an example
Saddle synovial joint
Concave and convex joint surfaces unite at saddle joints. An example is the metatarsophalangeal joint
Plane synovial joint
Permits gliding or sliding movements. Example is the acromioclavicular joint
Pivot synovial joint
Allows rotation; a round bony process fits into a bony ligamentous socket. Examples are the atlantoaxial joint and the proximal radio-ulnar joint
Condyloid synovial joint
Permits flexion, extension, adduction, abduction and circumduction. Metacarpophalangeal joint (middle of the hand)
Ball and socket synovial joint
Permits movement in several axis, an example is the glenohumeral joint
The articular cartilage of synovial joints is made up of
Hyaline cartilage
Describe the superficial/tangential layer of cartilage
Made up of flattened chondrocytes that produce collagen and glycoproteins (lubricin)
Describe the transitional layer of cartilage
Round chondrocytes that produce proteoglycans from superifical to deep levels
State the main functions of cartilage
Supporting the framework of organs, form the articulating surfaces of bones and growth and development of long bones
Which cartilage is the weakest
Hyaline cartilage
Describe the collagen fibres in hyaline cartilage
Widely dispersed thin type 2
Strongest type of cartilage
Fibrocartilage
Describe the structure of fibrocartilage
alternating layers of hyaline cartilage matrix and thick layers of dense collagen fibres orientated in the direction of functional stresses
Describe the structure of elastic cartilage
The chondrocytes are found in a threadlike network of elastic fibres in the matrix
What are the constituents of cartilage
Chondroblasts, chondrocytes and extracellular matrix (10% aggrecan, 75% water and a mix of collagen fibres)
State the function of chondroblasts
Secrete matrix and fibres into the ECM of cartilage
What are chondrocytes
Trapped chondroblasts which have matured into chondrocytes
What are lacunae
Matrix encolsed comparments that chondrocytes sit in
The surface of most cartilage is covered by
A layer of dense irregular connective tissue called the perichondrium
What does the outer layer of the periochondrium contain
Collagen producing fibroblasts
What does the inner layer of the perichondrium contain
Chondroblasts
What is the vascularity of cartilage
Avascular
How does cartilage get nourished
Long range diffusion from nearby capillaries in the perichondrium
Interstitial growth of cartilage
Chondrocytes grow and divide and lay down more matrix inside existing cartilage
Appositional growth of cartilage
New surface layers of matrix are added to the pre-existing matrix by new chondroblasts from the perichondrium
How is articular cartilage nourished
From the synovial fluid produced by the synovial membrane
What cells produce synovial fluid
Synoviocytes
Type A synoviocytes
Look like macrophages. These remove debris and contribute to fluid production.
Type B synoviocytes
Fibroblast-like and main producer of synovial fluid
What is synovial fluid made up of
- Viscous fluid
- Hyaluronic acid and lubricin, collagenases and proteinases
- Fluid component
State the functions of synovial fluid
Nutrition of articular cartilage, removal of waste products and lubrication
Describe the process of lubrication
boundary including glycoproteins such as lubricin bind to receptors on articular surfaces to form a thin film. It is hydrodynamic – surfaces kept apart by liquid pressure and viscosity changes with load and velocity of movements
What happens to the viscosity of synovial fluid as age increases
Increases, slower joint movements and reduced lubrication
What happens to the water content of cartilage as age increases
Decreases - therefore reduced shock absorption
