Principles of articulation Flashcards
What is an articulation/joint/arthrosis?
a point of contact between:
neighbouring bones
bone and cartilage
bone and teeth
How are different types of joint classified?
- structure
- function
- movement
Give some examples of shoulder articulation
glenohumeral
sternoclavicular
acromioclavicular
Describe structural classification of a joint
Presence or absence of a synovial cavity and the type of connective tissue.
Described as either fibrous, cartilaginous, or synovial
Describe the functional classification of a joint
Based on the degree of movement permitted:
Synarthrosis (immovable)
Amphiarthrosis (partially moveable)
Diarthrosis (freely moveable)
Describe the structure of fibrous joints
No synovial cavity
Held together by a fibrous connective tissue
What is the function of fibrous joints?
Permits little or no movement (synarthrosis/amphiarthrosis)
List the 3 types of fibrous joint
- Suture
- Syndesmosis
- Interosseous membrane
Describe a suture
Unite skull bones
Thin layer of dense connective tissue
Irregular
Interlocking edges provide strength, permit no movement (synarthrosis)
hat does ossification of a suture form?
synostosis
Give an example of a synostosis
left & right sides of frontal bone fuse ~6 years of age
Describe a syndesmosis
More connective tissue than seen in a suture
Crosses a greater distance than a suture
Connective tissue typically arranged into bundles (ligament)
What is the function of a syndesmosis
Typically permit slight movement (amphiarthrosis)
Give some examples of a syndesmosis
Anterior tibiofibular ligament
Gomphosis
Describe interosseous membranes
Sheet of dense connective tissue
Binds adjacent long bones
Amphiarthrosis
Give some examples of interosseous membranes
between the radius and ulna in forearm, and tibia and fibia in the leg
Describe cartilaginous joints
No synovial cavity
Held together by a fibrocartilage or hyaline cartilage
Permits little or no movement (synarthrosis/amphiarthrosis)
Give some examples of cartilaginous joints
Synchrondosis
Symphysis
Describe synchrondosis
The connective tissue is hyaline cartilage
Synarthrosis
Give an example of a synchrondosis
epiphyseal plate (growth plate)
What happens to the epiphysis, metaphysis and epiphyseal plate at skeletal maturity?
fuse forming a synostosis
Describe a symphysis
Connective tissue is fibrocartilage
Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones
Amphiarthrosis
Where do symphysis occur? Give examples
All symphysis occur in the midline of the body:
Junction of the manubrium and sternum
Intervertebral discs
Pubic symphysis
Describe synovial joints
Synovial (joint) cavity between articulating bones
Freely moveable - diarthrosis
Layer of hyaline cartilage called articular cartilage
Describe the articular cartilage
Covers the bones at synovial joints
Avascular
Composed of collagen and proteoglycan
Orientation of collagen structure imparts resistance to compression & an extremely low resistance surface
Describe the 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 articular fat pads
Describe 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
Supplyies nutrition to, and removes waste products from the avascular articular cartilage
Phagocytes remove microbes and debris
Describe the accessory ligaments of the synovial joint
Intracapsular ligaments lie within the joint capsule
- Excluded from synovial fluid by folds in synovial membrane - e.g. anterior and posterior cruciate ligaments of the knee
Extracapsular ligaments lie outside the joint capsule
- e.g. fibular and tibial collateral ligaments of the knee
Describe the accessory articular discs
Fibrocartilage pads lie between articular cartilage of some synovial joints e.g.meniscus of the knee
Called meniscii or articular discs
Help maintain joint stability
Direct the flow of synovial fluid
What pathology can happen in the accessory articular discs
Meniscal tears - common in athletes
Describe the nerve supply of the synovial joint
Nerve endings same as those that supply associated muscles
Distributed to the articular capsule and associated ligaments
Pain and proprioception
Describe the blood supply of the synovial joint
Many components of the synovial joint are avascular
Rely on numerous branching of arteries and veins to supply associated tissue
What are bursae?
Bursae are fluid filled sacs lined with synovial like membrane
Bursae cushion movement between body parts
What are tendon sheaths?
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
List the different types of synovial joint based on movement
Planar Hinge Pivot Condyloid Saddle Ball & Socket
Describe planar joints and give examples
Surfaces flat or slightly curved
Permit back and forth, and side to side movements
Examples include:
- intercarpal joints (between carpal bones at the wrist)
- intertarsal joints (between tarsal bones at the ankle)
Describe hinge joints and give examples
Concave surface of one bone fits the convex surface of another Permits motion in a single axis (flexion and extension) Examples include: - knee joints - elbow joints
Describe pivot joints and give examples
Rounded or pointed surface of one bone
pivots inside a ring formed by the other bone and a ligament
Permits rotation in it’s longitudinal axis (monoaxial)
Examples include:
- radioulnar joints
- atlanto-axial joint
Describe condyloid joints and give examples
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 include:
- wrist joint
- metacarpophalangeal joints
Describe saddle joints and give examples
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 include:
- carpometacarpal joint
Describe ball and socket joints and give examples
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 include:
- shoulder joint
- hip joint
Describe the structure of the ball and socket 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
Glenoid labrum; a narrow rim of fibrocartilage – deepens glenoid
Stabilised by three ligaments:
glenohumeral
coracohumeral
transverse humeral
Four associated bursae
Describe the rotator cuff muscles
Most strength from rotator cuff muscles supraspinatus infraspinatus teres minor subscapularis Join the scapula with the humerus Encircle the joint and fuse with joint capsule
Describe the acromioclavicular joint
Technically a synovial gliding joint (planar) but it acts like a pivot
Joint between the acromion (part of the scapula) and the clavical
Stabilised by three ligaments:
acromioclavicular
coracoacromial
coracolclavicular (conoid and trapezoid)
Allows the movement of the scapula, permitting greater arm rotation (above the head)
Describe the 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
Reinforced by interclavicular, anterior, and posterior sternoclavicular ligaments
Although a saddle joint – is capable of triaxial movement – all movement is passive
