Joints General anatomy

Joints Union between 2 or more bones Joint or articulation Stable union Free movement Types of tissue connecting bones

Structural classification Depending on the presence or abscense of a joint cavity Synarthroses or solid joints Diarthroses or cavitated joints

Synarthroses Depending on the type of connective tissue that binds the joints these are further classified into 2 varieties Fibrous joint Cartilaginous joint

Fibrous joint Bones are united by means of fibrous connective tissue Immovable Allow slight movement Subtypes : Sutures Syndesmoses Gomphoses

Cartilaginous joints 2 bones are connected by cartilage---cartilaginous joints Subtypes: Synchondroses Primary cartilaginous joints 2. Sympheses Secondary cartilaginous joints

Diarthroses Cavitated joints Synovial joints Permit free movement Joint cavity Articular disc Menisci Labra

Fibrous capsule Articular cartilage Synovial fluid Synovial membrane

Fibrous joint

Sutures Amount of connective tissue is minimal Sutures are found in skull only Movement at sutures In adults fibrous connective tissue is replaced by bone Synostosis Bones show reciprocal adapted irregularities Interlocking

Classification of sutures Depending on the shape of bone edges Serrate suture Denticulate suture Squamous suture Plane suture Schindylesis

Serrate suture Saw like Sagittal suture

Denticulate suture Tooth like Lambdoid suture

Squamous suture Reciprocally bevelled Temporoparietal suture

Plane suture Flat surfaces Intermaxillary suture

Schindylesis Ridge bone fits into a groove Suture between vomer and sphenoid

Syndesmosis Fibrous joint in which bony surfaces are held together by a fibrous interosseous ligament Inferior tibiofibular joint Inter transverse, inter spinous, supraspinous Interosseus membrane between radius and ulna

Gomphoses Conical process of one bone fits into socket of another bone Teeth and alveolar sockets No movement

Cartilaginous joints

Cartilaginous joints Synchondroses Symphyses

Synchondroses Uniting medium is hyaline cartilage Primary cartilaginous joints Not considered as true joints. No movement is possible Intracartilaginous method of ossification Growing ends of 2 bones or ossification centres of a bone Residual plate may persist

Important role in the growth of bone in length Between occipital and petrous temporal bones

Fate of synchondroses Temporary joints Allow growth When optimum length has been achieved, hyaline cartilage is replaced by osseous tissue

Symphyses Bones are joined by fibrocartilage Secondary cartilaginous joints Allow limited degree of movement Bony surfaces are coated with hyaline cartilage United by fibrocartilage (disc) Further united by ligamentous bands

Distribution Located in the median plane Between the pubic bons to form pubic symphysis Between the menubrium and the body of the sternum Between the bodies of vertebrae

Fate of symphyses Most of the symphyses are permanent Joints between bodies of successive sacral vertebrae Between sacram and coccyx Between coccygeal segments

Diarthroses

Articular cartilage Hyaline cartilage Functions: Wear resistant Lubrication Shock absorber

Blood vessels and nerves Has no nerves Insensitive No blood vessels Diffusion

Fibrous capsule Surrounds the joint in the form of a cuff Ends of cuff are attached to the articular ends of bones Attachment on short bones? Attachment on long bones? Holds the bones together Lax and pliable

Blood vessels and nerves fibrous capsule is perforated by blood vessels and nerves Synovial membrane may protrude as a sac= Bursa Prevent friction

Ligaments Bands of connective tissue For support and strength May exists as thickening of articular capsule= capsular ligament Accessory ligament (not a part of articular capsule) Extracapsular (coracoclavicular ligament) Intracapsular cruciate ligament of the knee joint)

Tough and inelastic Flexible and pliable Nonextensible Rich supply of sensory nerves Prevent stretching Sprain

Synovial membrane Thin sheet of connective tissue Rich in blood vessels and lymphatics Lines the inner surface of the fibrous capsule Covers intracapsular ligaments and tendon Absen tfrom articular disc and menisci In large joints: lines non-articular bone

Inner surfaces thrown into folds that projects into the joint cavity Accumulation of fatty pad = articular fat pads Situated between the membrane and fibrous capsule or bone Function: Joint cushion ill spaces and irregularities

Synovial Fluid Transparent viscous fluid Clear , pale yellow, viscous and shiny Synovia Functions: Lubricates the opposing articular surfaces Provide nutrition to articular cartilage, articular discs and menisci

Articular Discs Fibrocartilaginous discs Divide the joint cavity into compartments Disc may be complete Disc my be incomplete Fibrocartilage Disc is fused to the fibrous capsule Avascular

Functons of articular disc: Adjust unequal or incongruent articulating surfaces Shock absorbers Facilitate the occurrence of combined movements

Menisci Cresent shaped wedge of fibrocartilage 2 menisci in knee Shock absorbing cushion Improves the congruence between the articulating bone surfaces

Labra Pliable socket of Fibrocartilage Attached to the rim of the cartilage Serves to increase the depth of the socket Labrum glenoidale Labrum acetabulare