Joints Flashcards
What is the definition of a joint?
Connection between two bones in the skeleton
- Synovial= articular cavity
- Solid= connective tissue
Describe Cartilage
- Reinforces articulating surfaces
- Supports soft tissue structures
- Avascular, aneural
- Able to tolerate stress and maintain flexibility
What is the Ultrastructure (1) of cartilage?
- Produced by chondroblasts (flat irregular cells)
- Produces ECM which is composed mainly of collagen
What are Chondrocytes?
Chondroblasts that become less active with age
What is Lacunae?
Pools of ECM which contain the chondrocyte
What are the types of cartilage?
- Hyaline
- Fibrocartilage
- Elastic
How are joints classified?
-Type of tissue forming the joint
-Degree of movement across the joint:
=Fibrous tissue- synarthrosis movement
=Cartilaginous- amphiarthrosis movement
=Synovial- diarthrosis
What are fibrous joints?
- Strong joints made up of tough fibrous tissue
- Joined by dense connective tissue
- Collagen is main constituent
What are the types of fibrous joints?
- Sutures
- Gomphoses
- Syndesmoses
Describe Sutures
- Immobile (synarthrosis)
- Between flat bones of the skull
- Important during birth (deformation)
- Fixation around 20 years of age
Describe Gomphoses
- Immobile (synarthrosis)
- Between upper teeth and maxilla, and lower teeth and mandible
- Periodontal ligament
Describe Syndesmoses
- Slightly mobile (amphiarthroses)
- Bone bound together by interosseous membrane
- Middle radioulnar joint and middle tibiofibular joints
What are cartilaginous joints?
- Bones are connected by either hyaline or fibrocartilage
- Hyaline= glassy, semi-transparent
- Fibrocartilage= hybrid tissue between dense fibrous connective tissue and hyaline cartilage
What are the types of cartilaginous joints?
- Synchondroses
- Sympheses
Describe Synchondroses
- Hyaline cartilage between bones
- Immobile (synarthrosis)
- Between diaphysis and epiphysis or growing long bone
Describe Sympheses
- Fibrocartilage between bones
- Slightly mobile (amphiarthrosis)
- Pubic symphysis, intervertebral joints
What are synovial joints?
- Fluid filled cavity within fibrous joint capsule
- Highly mobile
- Most common joint type in body
- Subclasses (articular surface and movement)
- Articular capsule, articular cartilage, synovial fluid
What is the Articular Capsule?
-Continuous with periosteum
-Encloses the joint
-2 layers
=Fibrous layer (outer)- white fibrous tissue, capsular ligament
=Synovial layer (inner)- serous connective tissue, vascularized, synovium
-Synovium secretes synovial fluid and controls exchange of nutrients
Describe Articular Cartilage
- Articulating surfaces are covered in hyaline cartilage
- Cartilage reduces friction for movement and acts as shock absorber
What is synovial fluid?
-Lies in the joint cavity and acts to:
=Lubricate the joint
=Absorb shock
=Distribute nutrients to the articular cartilage (avascular)
What are Accessory Ligaments?
- Connective tissue
- Resist excess strain across joint
What are Bursae?
- Synovial fluid filled sac
- Protective, cushions joint
- Reduces friction
Describe the Innervation of Synovial Joints
- Articular nerves
- Hilton’s law: the nerves supplying a joint also supply the muscles moving the joint and the skin covering their distal attachments
Describe Synovial joint vasculature
- Articular arteries arise from vessels surrounding the joint
- Lie within the synovial membrane
- Form communications (anastomoses)
- Articular veins
What are the types of synovial joint?
- Hinge
- Saddle
- Plane
- Pivot
- Condyloid
- Ball and socket
Describe a Hinge joint
- Movement in 1 plane (flexion and extension)
- Found in the elbow, ankle and knee joints
Describe a Saddle joint
- Opposing articular surfaces (concave-convex)
- Found in carpometacarpal joints
Describe a Plane joint
- Flat articular surfaces
- Bones glide over each other
- Found in acromioclavicular joint of the shoulder and subtalar joint
Describe a Pivot joint
- Central bony pivot surrounded by ligamentous ring
- Allows rotational movement
- Found in atlantoaxial joint and proximal and distal radioulnar joints
Describe a Condyloid joint
- Also known as an ellipsoid joint
- Convex surface articulating with concave surface
- Found in joints of wrist, metacarpophalangeal and metatarsophalangeal joints
Describe a Ball and Socket joint
- Ball shaped surface of one bone articulating with cup shaped surface of another bone
- Highly mobile joint with movement across many axes
- Found in joints of the hip and shoulder
What are Synarthrosis joints?
- Immovable, fixed joint
- Fibrous connective tissue
- Provide protection
- Sutures of the skull
What are Amphiarthrosis joints?
- Slightly moveable
- Fibrous and cartilaginous joints
- Intervertebral joints of the spine, pubic symphysis of the pelvis
What are Diarthrosis joints?
- Freely moveable
- All synovial joints
- Appendicular skeleton
- Uniaxial, biaxial, multiaxial
What is uniaxial?
- Movement in 1 plane
- Hinge: elbow, knee, ankle
What is biaxial?
- Movement in 2 planes
- Condyloid: metacarpophalangeal joints
What is multiaxial?
- Movement in several planes (3 axes)
- Ball and Socket joints: shoulder, hip
What factors affect joint stability?
- Articular surfaces= size, shape, arrangement
- Ligaments= number, rigidity
- Muscle= tone, arrangement
Describe the role of ligaments in joint stability
- The more ligaments a joint has and the more rigid they are, the more stable the joint will be
- Reduce movement across a joint
Describe the role of muscles in joint stability
- Increased muscle tone around a joint increases joint stability
- Rotator cuff muscles around the shoulder joint
