L10 The principles of articulation: fibrous, cartilaginous and synovial joints Flashcards
Articulation/joint/arthrosis
Point of contact between:
- Neighbouring bones
- Bone and cartilage
- Bone and teeth
How are joints classified
- Structure
- Function
- Movement
Structural classification
- Presence or absence of a synovial cavity and the type of connective tissue
- Described as either fibrous, cartilaginous or synovial
Functional classification
Based on the degree of movement permitted:
- Synarthrosis (immovable)
- Amphiarthrosis (partially moveable)
- Diarthrosis (freely moveable)
Fibrous joints
- No synovial cavity
- Held together by a fibrous connective tissue
- Permits little or no movement (synarthrosis/amphiarthrosis)
Types of fibrous joints
- Suture
- Syndemosis
- Interosseous membrane
Fibrous joints - suture
- Unite skull bones
- Thin layer of dense connective tissue
- Irregular
- Interlocking edges provide strength, permit no movement (synarthrosis)
- Ossification of a suture forms a synostosis
Fibrous joints- syndesmosis
- More connective tissue than seen in a suture
- Crosses a greater distance than a suture
- Connective tissue typically arranged into bundles (ligament)
- Typically permit slightly movement(amphiarthrosis)
Examples of synesmosis in fibrous joints
Between fibula and tibia - anterior tibiofibular ligament
Gomphosis (or dentoalveolar)
Fibrous joints - interosseous membranes
- Sheet of dense connective tissue
- Binds adjacent long bones
- Amphiarthrosis
Examples of interosseous membranes in fibrous joints
Two main examples between the radius and ulna in forearm, and tibia and fibia in the leg
Cartilaginous joints
- No synovial cavity
- Held together by a fibrocartilage or hyaline cartilage
- Permits little or no movement (synarthrosis/amphiarthrosis)
Types of cartilaginous joints
- Synchrondosis
2. Symphysis
Cartilaginous joints - synchrondosis
- The connective tissue is hyaline cartilage
- Synarthrosis
- Example - epiphyseal plate (growth plate)
- At skeletal maturity the epiphysis, metaphysis and epiphyseal plate fuse forming a synostosis
Cartilaginous joints - symphysis
- Connective tissue is fibrocartilage
- Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones
- Amphiarthrosis
Where do all symphysis occur
All symphysis occur in the midline of the body:
- Junction of the manubrium and sternum
- Intervertebral discs
- Pubic symphysis
Synovial joints
- Synovial (joint) cavity between articulating bones
- Freely moveable - diarthrosis
- Layer of hyaline cartilage called articular cartilage
Synovial joint structure - articular cartilage
- Covers the bones at synovial joints
- Avascular
What is articular cartilage composed of
- Composed of collagen and proteoglycan
- Orientation of collagen structure imparts resistance to compression and an extremely low resistance surface
Synovial joint structure - articular capsule
- Encapsulates a synovial joint
- Composed of two layers
- Outer fibrous membrane connects to periosteum (flexibility permits movement, fibres arranged into bundles - high tensile strength)
- Inner layer termed synovial membrane (areolar connective tissue rich in elastic fibres occasionally contains structural fat pads
Synovial joint structure - synovial fluid
- Secreted by synovial membrane
- Rich in hyaluronic acid, secreted by fibroblast-like cells, and interstitial fluid from blood plasma
- Lubricates articular surface (reducing friction)
- Provides some shock-absorbing properties
- Supplies nutrition to, and removes waste products from the avascular articular cartilage
- Phagocytes remove microbes and debris
Synovial joint structure - accessory ligaments
Intracapsular and extracapsular ligaments
Location of intracapsular ligaments
Intracapsular ligaments lie within the joint capsule
- Excluded from synovial fluid by folds in synovial membrane
- eg. anterior and posterior cruciate ligaments of the knee
Location of extracapsular ligaments
Outside the joint capsule
- eg. fibular and tibial collateral ligaments of the knee
Synovial joint structure - accessory articular discs
- Fibrocartilage pads lie between articular cartilage of some synovial joints eg meniscus of the knee
- Called meniscii or articular discs
- Help maintain joint stability
- Direct the flow of synovial fluid
- Meniscal tears (common in athletes)
Synovial joint structure - nerve and blood supply
- Nerve endings same as those
- Distributed to the articular capsule and associated ligaments
- Pain and proprioception
- Many components of the synovial joint are avascular
- Rely on numerous branching of arteries and veins to supply associated tissue
Synovial joint structure - bursae and tendon sheaths
- Moving parts of joints can cause friction
- Bursae are fluid filled sacs lined with synovial like membrane
- Bursae cushion movement between body parts
- Tendon sheaths are similar to bursae
- Specialised membranes that wrap around tendons
- Especially where many tendons come together and/or pass through a synovial joint capsule
Types of synovial joints - movement
- Planar
- Hinge
- Pivot
- Condyloid
- Saddle
- Ball and socket
Planar synovial joints
- Surfaces flat or slightly curved
- Permit back and forth, and side to side movements
Examples of planar joints
- Intercarpal joints (between carpal bones at the wrist)
- Intertarsal joints (between tarsal bones at the ankle)
Hinge synovial joint
- Concave surface of one bone fits the convex surface of another
- Permits motion in a single axis (flexion and extension)
Examples of hinge synovial joints
- Knee joints
- Elbow joints
Pivot joints
- Rounded or pointed surface of one bone pivots inside a ring formed by the other bone and a ligament
- Permits rotation in its longitudinal axis (monoaxial)
Examples of pivot joints
- Radioulnar joints
- Atlanto-axial joint
Condyloid joints
- Convex oval projection of one bone fit into the oval depression of the other
- Permits movement around two axis (biaxial; flexion and extension, and abduction and adduction)
Examples of condyloid joints
- Wrist joint
- Metacarpophalangeal joints
Saddle joints
- One bone fits into the saddle shaped bone it opposes
- Modified condyloid joint
- Permits movement around two axis(biaxial; flexion and extension, abduction and adduction, (sometimes limited rotation)
Examples of saddle joints
- Carpometacarpal joint
Ball and socket joint
- Ball-like surface of one bone fits into the cup-like depression of the other
- Triaxial movement around three planes (triaxial; flexion and extension, abduction and adduction, and rotation)
Examples of ball and socket joints
- Shoulder joint
- Hip joint
Glenohumeral (shoulder) joint
- Synovial ball and socket joint
- Joint between the proximal humerus and the scapula(glenoid fossa)
- Due to the shallowness of the glenoid cavity, it is the most mobile joint in the body
- Four associated bursae
What is the glenoid labrum
- A narrow rim of fibrocartilage - deepens glenoid
Which ligaments stabilise glenohumeral joint
- Glenohumeral
- Coracohumeral
- Transverse humeral
Rotator cuff muscles
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
Acromioclavicular joint
- Technically a synovial gliding joint(planar) but it acts like a pivot
- Joint between the acromion (part of the scapula) and the clavicle
- Allows the movement of the scapula, permitting greater arm rotation(above the head)
Sternoclavicular joint
- Synovial saddle joint
- Medial clavicle fits into a hollow formed by the superlateral surface of the manubrium and the medial costal cartilage of the first rib
- Fibrocartilagenous articular disc divides the joint into two synovial cavities
Ligaments reinforcing sternoclavicular joint
- Reinforced by interclavicular, anterior, and posterior sternoclavicular ligaments
- Although a saddle joint - is capable of triaxial movement - all movement is passive
