10. Principles of articulation Flashcards by Zahraa Alzoubeidi

What is an articulation?

An articulation or joint or arthrosis is a point of contact between:
neighbouring bones
bone and cartilage
bone and teeth

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Joint classification

Different types of joints classified by:

	- structure
	- function
	- movement

Example of ‘shoulder’ articulation:
glenohumeral
sternoclavicular
acromioclavicular

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Joint classification

Structural classification

Functional classification

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Structural classification

Presence or absence of a synovial cavity and the type of connective tissue.
Described as either fibrous, cartilaginous, or synovial

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Functional classification

Based on the degree of movement permitted:
Synarthrosis (immovable)
Amphiarthrosis (partially moveable)
Diarthrosis (freely moveable)

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Fibrous joints

No synovial cavity
Held together by a fibrous connective tissue
Permits little or no movement (synarthrosis/amphiarthrosis)

Three types of fibrous joint:

Suture
Syndesmosis
Interosseous membrane

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Suture

Fibrous joint

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
e.g. left & right sides of frontal bone fuse ~6 years of age

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syndesmosis

fibrous joint
More connective tissue than seen in a suture
Crosses a greater distance than a suture
Connective tissue typically arranged into bundles (ligament)
Typically permit slight movement (amphiarthrosis)

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examples of syndesmosis

anterior tibiofibular ligament (fibula to tibia)

gomphosis (dentoalveolar)

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interosseous membranes

Sheet of dense connective tissue
Binds adjacent long bones
Amphiarthrosis
Two main examples between the radius and ulna in forearm, and tibia and fibia in the leg

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Cartilaginous joints

No synovial cavity
Held together by a fibrocartilage or hyaline cartilage
Permits little or no movement (synarthrosis/amphiarthrosis)
Two types of cartilaginous joint:
1. Synchrondosis
2. Symphysis

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Synchrondosis

Cartilaginous joint

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

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Symphysis

Connective tissue is fibrocartilage
Adjacent bones lined with hyaline cartilage, but with a broad disc of fibrocartilage connects the bones
Amphiarthrosis
All symphysis occur in the midline of the body:
Junction of the manubrium and sternum
Intervertebral discs
Pubic symphysis

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Synovial joints

Synovial (joint) cavity between articulating bones
Freely moveable - diarthrosis
Layer of hyaline cartilage called articular cartilage

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Articular cartilage

a synovial joint structure

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

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Articular capsule - a synovial joint structure

Encapsulates a synovial joint
Composed of two layers:
1. outre fibrous membrane connecting to periosteum
2. Inner layer termed synovial membrane

Outer fibrous membrane of articular capsule

Outer fibrous membrane connects to periosteum

Flexibility permits movement
Fibres arranged into bundles – high tensile strength

Synovial membrane

Inner layer of articular capsule

areolar connective tissue rich in elastic fibres
occasionally contains structural articular fat pads

Synovial fluid - synovial joint structure

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

Accessory ligaments of synovial joints

Intracapsular ligaments 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 outside the joint capsule
- e.g. fibular and tibial collateral ligaments of the knee

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

Meniscal tears (common in athletes)

Nerve and blood supply to synovial joints

Nerve endings same as those that supply associated muscles
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

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 &amp; Socket

Types of synovial joints - planar

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)

Types of synovial joints - hinge

``` 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 ```

Types of synovial joints - pivot

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

Types of synovial joints - condyloid

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

Types of synovial joints - saddle

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: - d1 carpometacarpal joint

Types of synovial joints - ball and socket

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

joint systems example

Interactions between humerus, scapula, clavicle, and sternum, allow wide ranging movement. The component joints include: acromioclavicular sternoclavicular glenohumeral

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 ``` Glenoid labrum; a narrow rim of fibrocartilage – deepens glenoid Stabilised by three ligaments: - glenohumeral - coracohumeral - transverse humeral Four associated bursae ```

glenohumeral joint - 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

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 Stabilised by three ligaments: -acromioclavicular -coracoacromial -coracolclavicular (conoid and trapezoid) 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 Reinforced by interclavicular, anterior, and posterior sternoclavicular ligaments Although a saddle joint – is capable of triaxial movement – all movement is passive

What is the most mobile joint in the body?

Glenohumeral joint | because of the shallowness of the glenoid cavity