BSC 215 1nd EditionExam # 3 Study Guide Chapters 9-12Chapter 9: Joints9.1 Joints and Their Classification Any point where two bones meet is called a joint (articulation), whether or not the bones are mobile at that interface The science of joint structure, function, and dysfunction is called arthrology  The study of muscle musculoskeletal movement is kinesiology The name of the joint is typically derived from the names of the bones involvedo For example: the atlanto-occipital joint is where the atlas meets the occipital condyles Joints can be classified according to the manner in which the adjacent bones are bound to each other. There are four categories: bony, fibrous, cartilaginous, and synovial joints A bony joint is an immobile joint formed the gap between two bones ossifiesand they become a single boneo In infants, there are two frontal bones that eventually fuse together and become one bone A fibrous joint is a point at which adjacent bones are bound by collagen fibers that emerge from one bone, cross the space between them, and penetrate into the other There are three kinds of fibrous joints: sutures, gomphoses, and syndesmoseso Sutures are immobile or only slightly mobile fibrous joints that closely bind the bones of the skull to each other; they occur no where else Serrate sutures appear as wavy lines along which the adjoining bones firmly interlock with each other by their serratedmargins – coronal, sagittal, and lamboid sutures Lap (squamous) sutures occur where two bones have overlapping beveled edges – between temporal and parietal bones Plane (butt) sutures occur where two bones have straight nonoverlapping edges – intermaxillary suture in the roof of the moutho Gomphoses is the attachment of a tooth to its socket o The tooth is held firmly in place by a fibrous periodontal ligamento A syndesmoses is a fibrous joint at which two bones are bound by relatively long collagenous fibers – more mobility than the other two – between radius and ulna A cartilaginous joint is also called an amphiarthrosis – two bones are linked by cartilage There are two types: synchondroses and symphyseso A synchondrosis is a joint in which the bones are bound by hyaline cartilage – temporary joint between the epiphysis and diaphysis of the long bone of a childo In a symphysis, two bones are joined by fibrocartilage – the pubic symphysis9.2 Synovial Joints The most familiar type of joint is the synovial joint, also called diarthrosis Many synovial joints are freely mobile and some have more limited mobility such as the wrist and ankle bones Synovial joints are the most structurally complex type of joint and are the type most likely to develop uncomfortable and crippling dysfunctions In synovial joints, the facing surfaces of the two bones are covered with articular cartilage, a layer of hyaline cartilage  These surfaces are separated by a narrow space, the joint (articular) cavity, containing a slippery lubricant called synovial fluido This fluid nourishes the articular cartilages, removes their wastes, and makes movements at synovial joints almost friction-free A connective tissue joint (articular) capsule encloses the cavity and retains the fluid and is covered with a synovial membrane In a few synovial joints, fibrocartilage grows inward from the joint capsule and forms a pad between the articulating bones – the pad crosses the entire joint capsule and is called an articular disc  In the knee, two cartilages extend to the left and right but do not entirely cross the joint and each are called a meniscus  A tendon is a strip or sheet of tough collagenous connective tissue that attaches a muscle to a bone A ligament is a similar tissue that attaches one bone to another A bursa is a fibrous sac filled with synovial fluid, located between adjacent muscles, where a tendon passes over a bone, or between bone and skin Tendon (synovial) sheaths are elongated cylindrical bursae wrapped around a tendon, especially seen in the hand and foot In skeletal anatomy, the fulcrum is a joint; the effort is applied by a muscle; and the resistance can be an object against which the body is working, the weight of the limb itself, or the tension in an opposing muscle The mechanical advantage (MA) of a lever is the ratio of its output force to its input force If MA is greater than 1.0, the lever produces more force, but less speed or distance, than the force exerted on ito If MA is less than 1.0, the lever produces more speed or distance, but less force, than the input Most musculoskeletal levers operate with an MA much less than 1 There are three classes of levers that differ with respect to which component is in the middle – the fulcrum (F), effort (E), and resistance (R)o A first-class lever is one with the fulcrum in the middle (EFR), such as a seesaw Example: atlanto-occipital joint of the neck – opposes tendency to tip head forwardo A second-class lever has the resistance in the middle (FRE) Example: when bouncing a child on your thigh, the femur pivotson the hip joint and the quadriceps femoris muscle of the anterior thigh elevates the tibia (the resistance is the weight of the child)o In a third-class lever, the effort is applied between the fulcrum and resistance (REF) Example: paddling a canoe – stationary grip at the handle is thefulcrum, the effort is applied in the middle, and resistance is thewater at the blade One aspect of joint performance and physical assessment of a patient is a joint’s flexibility, or range of motion (ROM) – the degrees through which a joint can move The ROM of a joint is determined by: o Structure of the articular surfaces of the bones (shapes of the bone surfaces)o Strength and tautness of ligaments and joint capsules (ligaments can limit movement that bones alone do not)o Action of the muscles and tendons (knee is limited by hamstring muscles) A moving bone has a relatively stationary axis of rotation that passes through the bone in a direction perpendicular to the plane of movement  Because the arm can move in all three anatomical planes, the shoulder joint is said to have three degrees of freedom, or to be a multiaxial joint Other joint only move through one or two planes; they have one or two degrees of freedom and are called monaxial and biaxial joints, respectively There are 6 fundamental types of synovial joints:o