Chapter 8 joints word doc notes PDF

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CHAPTER 8: JOINTS Joints (articulations): the site where two bones meet - Determines how one bone moves relative to another bone it articulates with - Articulate/articulations: an area where two bones are attached for the purpose of motion of body parts General function of joints: 1. Mobility – allow for (varying) movement of different body parts 2. Stability – hold the skeleton together a. Hold bones in place b. Prevents damage to internal structures Classifications of Joints: 1. Structural – type of tissue that connects the bone at the articulating surface a. Types: fibrous, cartilaginous, synovial i. Fibrous – joints composed of collage fibers of connective tissue, contain no joint cavity 1. Sutures: found only in the bones in the skull, composed of extremely strong and short collage fibers, permits very little movement (exception: fontanels in infants), and sutures can eventually ossify over time to form syntoses 2. Syndemoses: bones are connected to one another only by ligaments (bands of fibrous tissue that bond bone to bone) a. short ligament = limited movement b. long ligament = greater degree of movement 3. Gomphoses: only joint type that does not join bone to another bone  joins tooth to bony alveolar socket a. Periodontal ligament  joins the bone of the mandible and the bone of the maxilla to the cementum of tooth ii. Cartilaginous – bones joined by hyaline cartilage, no joint cavity 1. Synchondroses – bones united with a plate of hyaline cartilage, mostly synarthroses a. Examples include epiphyseal plate in long bones, and costal rib cartilage 2. Symphyses – fibrocartilage joins bone, limited movement allowed, excellent shock absorbers a. Examples include intervertebral joints and pubic symphyses iii. Synovial – structurally more complex than cartilaginous or fibrous joints, most joints in the body fall under this classification, almost all located in the appendicular skeleton, considered diarthroses given that they provide a significant amount of movement compared to fibrous/cartilaginous

1. 6 structures found in all synovial joints: a. Articular cartilage- provides “cushion” to prevent damage when weight is applied on joint b. Joint cavity – small space between articulating bones c. Articular capsule – two layered capsule that encloses the joint cavity d. Synovial fluid – reduces friction between articular cartilages of articulating bones e. Reinforcing ligaments – bandlike ligaments that joint articulating bones, their function is to reinforce joints to provide extra stability i. Capsular ligaments – part of the outer layer of the joint capsule ii. Extracapsular ligaments - found outside the joint capsule iii. Intracapsular ligaments – ligament found deep to the joint capsule (but not in the joint capsule) f. Innervation and vascularization – joints supplies with sensory nerve fibers/ rich blood supply to joints 2. Structures that may or may not be associated with synovial joints: a. Bursae – flattened sacs that contain a small amount of synovial fluid, usually found where ligaments, muscles, skin, tendons, and or bones would rub together  function is to decrease friction between adjacent structures b. Tendon sheath – elongated bursa that wraps completely around a tendon subjected to frequent friction  function is to prevent excessive friction for a particular tendon 2. Functional – amount of movement allowed at the joint a. Types: synarthroses (no movement), amphiarthroses (limited movement), and diarthroses (free movement, mainly concerns appendicular skeleton) Joint Stability Several factors that affect joint stability: 1. Articular surfaces – the better two bones fit together, the more stable the joint 2. Ligaments – the more ligaments, the stronger the joint 3. Muscle tone – allows for bracing in joints, basically the most important factor when determining joint stability  makes sure that your muscles are able to respond to any stimuli

Movement allowed by synovial joints:

1. Nonaxial movement: results in gliding motion  involved in flat articular surfaces on both bones. Ex include plane joint in intercarpal and intertarsal joints, and vertebrae 2. Uniaxial movement: movement allowed in one axis only  the movements allowed include flexion, extension, and rotation. One fixed point in the joint where it will allow the joint to move 3. Biaxial movement: contain two axes of movement  movements allowed include flexion and extension, and adduction and abduction. Ex include condylar joint in knuckle and saddle joint at the base of the thumb 4. Multiaxial movement: allow for multiple axes of movement  flexion/extension, abduction/adduction, rotation. Ex include ball and socket joints of shoulders and hips Specific examples of synovial joints 1. Temporomandibular joint: where the mandible articulates to the temporal bone, modified hinge joint 2. Glenohumeral (shoulder) joint: where the humerus articulates to the glenoid fossa of the scapula, ball and socket joint, most freely moving joint in the body 3. Elbow joint: where the humerus articulates with the unla 4. Coxal joint: where the head of the femur articulates with the os coxa  another ball and socket joint that is very stable and hard to dislocate 5. Knee joint: single joint cavity that is shared by three separate joints a. Femororpatellar joint: between patella and femur b. Tibiofemoral joint: between femur and tibia Homeostatic imbalances of joints: - Cartilage tears o Joint cartilage (usually menisci) is overstretched, can snap and break o Compression and shear stress occur simultaneously o Joint is less table after injury - Sprains o Ligaments reinforcing joints are damaged  Stretch/partial tear: ligament is capable of healing on its own but this is a rather slow process  Completely torn ligament is very difficult to repair - Dislocation and sublocations o Occurs when joints come out of alignment o Some joints more likely to dislocate than others  Stable joints – less likely  Less stable joints – more likely  Loss of stability after dislocation  the joint is more likely to dislocate in the future - Arthritis o Can be inflammatory or degenerative o Widespread disease

o Can be acute or chronic o Types of arthritis:  Osteoarthritis(OA)  Most common form of chronic arthritis  Older individuals typically affected  Poorly aligned or overused joints most likely to exhibit this kind of arthritis  More articular cartilage destroyed than replaced  Exposed bone tissue rubs together, forming bone spurs  Deforms bone ends ultimately restricting movement at joints  Rheumatoid arthritis (RA)  Autoimmune chronic inflammatory disorder  More women affected than men  Bilateral degenerative condition  joints of fingers, wrist, ankle, feet most likely to be affected  Individuals affected have flare ups followed by periods of remission  Pain and swelling in joints  Progression of RA o Synovial membranes become inflamed o Lymphocytes and macrophages flood area to destroy cause of inflammation  Release chemicals in such large amounts that it destroys healthy tissue as well  Macrophages also destroy some of synovial membrane o Accumulation of synovial fluid and formation of a pannus  Pannus is a thickened portion of the synovial membrane  Breaks down cartilage tissue over time  Ankylosis can occur  Scar tissue forms where cartilage tissue once was, fusing bones together...