Joints, Synovial Fluid and Cartilage Flashcards
What are the 3 broad types of joint?
Fibrous - densely packed collagen - very strong and under tension
Cartilaginous - layer of hyaline cartilage found in between bones rather than densely packed fibrous collagen
Synovial - cavity, synovial fluid, all work to provide as low a friction environment as possible for best articulation and movement
What are 3 places where you might find a fibrous joint?
Cranial Sutures
Periodontal ligaments
Interosseous membranes - between forearm and lower leg bones, very tough and strong. Although important to note that they don’t prevent pronation etc due to the orientation of the densely packed collagen fibres
What are the 2 types of cartilaginous joint?
Primary cartilaginous (synchrondoses) - only hyaline cartilage joins the two bones; typically found in the epiphyseal growth plates of developing long bones.
Secondary cartilaginous (symphyses) - hyaline AND fibrocartilage found; e.g. an IV disc where there is a fibrocartilage disc and hyaline cartilage covering the bone.
What are some common features in almost all synovial joints?
Synovial cavity Articular cartilage 2 types of membrane: Synovial membrane on the inside (secretes synovial fluid) Fibrous capsule on the outside
What are some features found in some, but not all, synovial joints?
Articular discs
Ligaments
Bursae (fluid filled cushioning sacs that prevent friction in joints)
What are 6 different types of synovial joint?
Plane Condylar Hinge Saddle Pivot Ball and Socket
What 3 key factors are important in joint stability?
Shape of the articulating surfaces
Capsule and ligaments of the joints (strength)
Stabilising musculature - especially with things like rotator cuffs in the shoulder
What kind of cartilage are menisci made up of?
Fibrocartilage
What are a few features that can help differentiate hyaline and fibrocartilage?
Fibrocartilage has densely packed collagen fibres making it very mechanically strong; hyaline still has collagen but is much less densely packed
What differences can be seen through the different layers of hyaline (articular) cartilage?
Superficial/Tangential layer - chondrocytes are flatter and produce collagen and glycoproteins like lubricin
Transitional layer - chondrocytes are rounder and produce more proteoglycans like aggrecan (binds water really well)
Collagen fibres change orientation from superficial to deep (horizontal to vertical). Orientation tells you about the main direction of forces on the cartilage.
What percentage of hyaline cartilage is water and what is its significance?
> 75% (thanks to the binding properties of aggrecan)
It is incompressible so the cartilage is really strong under compression
What are the 3 key attributes of cartilage in general? (3 A’s)
Avascular
Aneural
Alymphatic
How does cartilage maintain a supply of nutrients and get rid of waste?
Via synovial fluid produced by the synovial membrane/synovium
Describe the synovium
Made up of tendon-like sheets
Synoviocytes present constantly producing synovial fluid
Rich capillary network to supply nutrients
No epithelial lining so we get a direct exchange of nutrients and waste between blood and synovial fluid.
What are the 2 types of synoviocyte?
Type A - look like mAcrophages, remove debris and contribute to synovial fluid production
Type B - look like fiBroblasts and are the main producers of synovial fluid
