Unit 2 Joints Study Guide PDF

Unit 2: Joints Study Guide Joints and Articulation Classification of Joints Define a joint: Articulation - site where two or more bones meet The rigid elements of the skeleton meet at sites called joints Weakest parts of the skeleton Functions of a joint: ○ Giv...

Unit 2: Joints Study Guide Joints and Articulation Classification of Joints Define a joint: Articulation - site where two or more bones meet The rigid elements of the skeleton meet at sites called joints Weakest parts of the skeleton Functions of a joint: ○ Give the skeleton mobility ○ Hold the skeleton together, support. Compare the structural and the functional classification of joints: Structural classification focuses on the material binding bones together and whether a joint cavity is present. ○ There are three structural classifications of joints: Fibrous – bones united by collagenic fibers Sutures (short fibers) – immobile (synarthrosis) Syndesmosis (longer fibers) – slightly mobile (amphiarthrosis) and immobile Gomphosis (periodontal ligament) - immobile Cartilaginous – bones ends/parts united by cartilage Synchondrosis (hyaline cartilage) – immobile Symphysis (fibrocartilage) – slightly movable Synovial – bone ends/parts covered with articular cartilage and enclosed within an articular capsule lined with synovial fluid Plane, hinge, pivot, condylar, saddle, ball and socket – freely movable Functional classification focuses on the amount of movement allowed. ○ There are three functional classifications of joints: Synarthroses - immovable joints Amphiarthroses - slightly movable joints Diarthroses - freely movable joints Know the three types of cartilage, where they can be found and characteristics and functions of each: Hyaline ○ Provides support, flexibility and resilience ○ It’s the most abundant skeletal cartilage ○ The only type of fiber found in the hyaline cartilage matrix is a collage unit fibril, which forms networks that are too thin to be seen with a light microscope. ○ Found in: Articular - covers the end of long bones Costal - connects ribs to the sternum Respiratory - makes up the larynx and reinforces air passages Nasal - supports the structure of the nose Elastic ○ Similar to hyaline cartilage except its matrix contains many elastic fibers along with the delicate collagen fibrils. It’s more flexible and tolerates repeated bending ○ Found in the epiglottis and the external ear Fibrocartilage ○ An usual tissue that resists both strong compression and strong tensions ○ It consists of two rows of thick collagen fibers alternating with rows of chondrocytes ○ Found in intervertebral discs and menisci of the knee Fibrous Joints Bones joined by fibrous tissues, namely dense regular connective tissue. No joint cavity present Most are immovable There are 3 types: ○ Gomphoses (synarthrosis) ○ Sutures (synarthrosis) ○ Syndesmoses (amphiarthrosis) Gomphoses (periodontal ligament) Explain the location and characteristics of gomphoses: The peg-in-socket joint The only example is the articulation of a tooth with its socket. In this case, the connecting ligament is the short periodontal ligament. Sutures (short fibers) Describe the location and functions of sutures: Only occur between the bones of the skull and their fibrous tissue is continuous with the periosteum around these flat bones Bones are tightly bound by a minimal amount of fibrous tissue The edges of the joining bones are wavy and interlocking Sutures not only knit the bones together but also allow growth in youth so that the skull can expand with the brain during childhood. During middle age, the fibrous tissue ossifies and the skull bones fuse together. At this stage, the close sutures are more precisely called synostoses, literally meaning “bony junction”. The immovable nature of sutures is a protective adaptation. Syndesmoses (longer fibers) Name the locations of syndesmoses and describe their function: Bones are connected exclusively by ligaments, bands of fibrous tissue longer than those that occur in the suture. The name syndesmosis derives from the Greek word for “ligament.” Movement varies from immovable to slightly movable. The amount of movement allowed at a syndesmosis depends on the length of the connecting fibers. If the fibers are short, as in the distal tibiofibular articulation, little to no movement is allowed and the joint is synarthrotic. If the fibers are quite long, as in the interosseous membrane between the radius and ulna, a large amount of movement is possible and the joint is diarthrotic. Found in connections like the tibia and fibula, and the radius and the ulna Cartilaginous Joints Articulating bones are united by cartilage Lack a joint cavity There are two types: ○ Synchondroses ○ Symphyses Synchondroses (hyaline cartilage) Describe the locations and functions of synchondroses: A bar or plate of hyaline cartilage unites the bones All synchondroses are synarthrotic Examples include: ○ Epiphyseal plates of children ○ Joint between the costal cartilage of the first rib and the sternum Symphyses (fibrocartilage) Name the locations of symphyses and their functions in these locations: Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage Amphiarthrotic joints designed for strength and flexibility Examples include: ○ Intervertebral discs ○ Pubic symphysis of the pelvis Synovial Joints Distinguishing Features and Anatomy of Synovial Joints Describe the characteristics common to all synovial joints: Bone ends/parts covered with articular cartilage and enclosed within an articular capsule lined with a synovial membrane All synovial joints are free movable; diarthrotic. Examples include: All limb joints List the basic features of a synovial joint: Articular cartilage ○ The ends of the opposing bones are covered by articular cartilages composed of hyaline cartilage. These spongy cushions absorb compression placed on the joint and thereby keep the bone ends from being crushed Joint (synovial) cavity ○ Unique to synovial joints, the joint cavity is really just a potential space that holds a small amount of synovial fluid. Articular capsule ○ The joint cavity is enclosed by a two-layered articular capsule, or joint capsule. The outer layer is a fibrous capsule of dense irregular connective tissue that is continuous with the periosteum layer of the joining bones. It strengthens the joint so that the bones are not pulled apart. ○ The inner layer of the capsule is a synovial membrane composed of loose connective tissue. In addition to lining the joint capsule, this membrane covers all the internal joint surfaces not covered by cartilage. Its function is to make synovial fluid. Synovial fluid ○ The viscous liquid inside the joint cavity is called synovial fluid because it resembles raw egg white. Synovial fluid is primarily a filtrate of blood, arising from capillaries in the synovial membrane. It also contains special glycoprotein molecules, secreted by the fibroblasts in the synovial membrane, that make synovial fluid a slippery lubricant that eases the movement at the joint. Reinforcing ligaments ○ Some synovial joints are reinforced and strengthened by bandlike ligaments. Most often, the ligaments are intrinsic, or capsular; that is, they are thickened parts of the fibrous capsule itself. Nerves and vessels ○ Synovial joints are richly supplied with sensory nerve fibers that innervate the articular capsule. Some of these fibers detect pain, but most monitor how much the capsule is being stretched. ○ Synovial joints also have a rich blood supply. Most of the blood vessels supply the synovial membrane, where extensive capillary beds produce the blood filtrate that is the basis of synovial fluid. Explain the composition and function of synovial fluid in a typical synovial joint: Bursae - flattened, fibrous sacs lined with synovial membranes, containing synovial fluid Tendon sheath - elongated bursa that wraps completely around a tendon Both of these are often associated with synovial joints. Essentially closed bags of lubricant, these structures act like “ball bearings” to reduce friction between body elements that move over one another. Characteristics of Synovial Joints Explain the movement of a joint: The two muscle attachments across a joint are: Origin - attachment to the immovable bone Insertion - attachment to the movable bone These are described as movement along transverse, frontal or sagittal planes. Nonaxial ○ slipping movements only Uniaxial ○ Movement in one plane Biaxial ○ Movement in two planes Multiaxial ○ Movement in or around all three planes Compare and contrast the six types of synovial joints: Plane ○ Articular surfaces are essentially flat ○ Allow only slipping or gliding movements ○ Only example of nonaxial joints Hinge ○ Cylindrical projects of one bone bits into a trough-shaped surface on another ○ Motion is along a single plane ○ Uniaxial joints permit flexion and extension only ○ Examples include: Elbow Interphalangeal joints Pivot ○ Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another ○ Only uniaxial movement allowed ○ Examples include: Joint between the Axis and the dens Proximal radioulnar joint Condyloid or Ellipsoidal ○ Oval articular surface of one bones fits into a complementary depression in another ○ Both articular surfaces are oval ○ Biaxial joints permit all angular motions ○ Examples include: Radiocarpal (wrist) joints Metacarpophalangeal (knuckle) joints Saddle ○ Similar to condyloid joints but allow greater movement ○ Each articular surface has both a concave and a convex surface ○ Examples include: Carpometacarpal joint of the thumb Ball and socket ○ A spherical or hemispherical head of one bone articulates with a cuplike socket of another ○ Multiaxial joints permit the most freely moving synovial joints ○ Examples are: Shoulder Hip ○ Types of Levers Define a lever: A lever is a rigid bar that moves on a fixed point, the fulcrum, when a force is applied to the lever. The applied force, called the effort, is used to move a resistance, or load. Discriminate between the effort arm and the load in a lever: Compare and contrast the three types of levers in the human body: First-class levers ○ The fulcrum is located between the load and the point at which the effort is applied Second-class levers ○ The load is positioned between the fulcrum and the point the effort is applied Third-class levers ○ The point at which the effort is applied lies between the load and the fulcrum The Movements of Synovial Joints Gliding Motion Describe the gliding motion and name joints in which it occurs: One flat bone surface glides or slips over another similar surface ○ Examples: Intercarpal and intertarsal joints Between the flat articular process of the vertebrae Angular Motion Describe the angular motion: Flexion ○ Bending movement that decreases the angle of the joint Extension ○ Reverse of flexion; joint angle is increased Dorsiflexion and plantar flexion ○ Up and down movement of the foot Abduction ○ Movement away from the midline Adduction ○ Movement towards the midline Circumduction ○ Movement describes a cone in space Rotational Motion Explain rotational motion and name joints in which it occurs: The turning of a bone around its own long axis Examples: ○ Between the C1 and C2 ○ Hip ○ Shoulder Special Movements Explain what is meant by special movements and name examples of joints in which it occurs: Supination and pronation ○ Radius and ulna are parallel = supination ○ Radius and ulna are crossed = pronation Inversion and eversion ○ Inversion - rolling onto the outer edge of the foot ○ Eversion - rolling onto the inner edge of the foot Protraction and retraction ○ Protraction - moving the jaw forward; underbite ○ Retraction - moving the jaw back; no chin ○ Applies to scapula Elevation and depression ○ Elevation - closing the jaw ○ Depression - opening the jaw ○ Applies to scapula as well