Joints Joint Fundamentals

Joints (Articulations) Weakest parts of the skeleton Articulation – site where two or more bones meet Functions of joints Give the skeleton mobility Hold the skeleton together

Classification of Joints: Structural Structural classification focuses on the material binding bones together and whether or not a joint cavity is present The three structural classifications are: Fibrous Cartilaginous Synovial

Classification of Joints: Functional Functional classification is based on the amount of movement allowed by the joint The three functional classes of joints are: Synarthroses – immovable Amphiarthroses – slightly movable Diarthroses – freely movable

Fibrous Structural Joints The bones are joined by dense, connective fibrous tissues There is no joint cavity Most are immovable There are three types – sutures, syndesmoses, and gomphoses

Fibrous Structural Joints: Sutures Occur between the bones of the skull Comprised of interlocking junctions completely filled with connective tissue fibers Bind bones tightly together, but allow for growth during youth In middle age, skull bones fuse and are called synostoses

Fibrous Structural Joints: Sutures Figure 8.1a

Fibrous Structural Joints: Syndesmoses Bones are connected by a fibrous tissue ligament Movement varies from immovable to slightly variable Examples include the connection between the tibia and fibula, and the radius and ulna

Fibrous Structural Joints: Syndesmoses Figure 8.1b

Name two functions of joints. Review Name two functions of joints. Name three structural classification of joints. Name three functional classification of joints. Name three types of fibrous joints. Where is the most prominent place to find suture joints. Name one example of Syndesmoses joint. Joint Fundamentals

Fibrous Structural Joints: Gomphoses The peg-in-socket fibrous joint between a tooth and its alveolar socket The fibrous connection is the periodontal ligament

Cartilaginous Joints Articulating bones are united by hyaline cartilage or disks of fibrocartilage Lack a joint cavity Two types – synchondroses and symphyses

Cartilaginous Joints: Synchondroses A bar or plate of hyaline cartilage unites the bones Examples include: Epiphyseal plates of children Joint between the costal cartilage of the first rib and the sternum

Cartilaginous Joints: Synchondroses Figure 8.2a, b

Cartilaginous Joints: Symphyses 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 joints and the pubic symphysis of the pelvis

Cartilaginous Joints: Symphyses Figure 8.2c

Synovial Joints Those joints in which the articulating bones are separated by a fluid-containing joint cavity Ends of the bones are covered in hyaline cartilage and the ends are encapsulated by synovial fluid All are freely movable Examples – all limb joints, and most joints of the body

Synovial Joints: General Structure Synovial joints all have the following Articular cartilage Joint (synovial) cavity Articular capsule Synovial fluid Reinforcing ligaments

Synovial Joints: General Structure Figure 8.3a, b

Table 8.2.1

Table 8.2.2

Table 8.2.3

Ball-and-Socket Joints Types of Synovial Joints Ball-and-Socket Joints 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: shoulder and hip joints

Ball-and-Socket Joints Figure 8.7f

Condyloid Joints Oval articular surface of one bone fits into a complementary depression in another Both articular surfaces are oval Biaxial joints permit all angular motions Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints

Condyloid Joints Figure 8.7d

Planar Joints One flat bone surface glides or slips over another similar surface Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae

Planar Joints Figure 8.5a

Hinge Joints Hinge joints Cylindrical projections of one bone fits into a trough-shaped surface on another Motion is along a single plane Uniaxial joints permit flexion and extension only Examples: elbow and interphalangeal joints

Hinge Joints Figure 8.7b

Pivot Joints Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another Only uniaxial movement allowed Examples: joint between the axis and the dens, and the proximal radioulnar joint

Pivot Joints Figure 8.7c

Similar to condyloid joints but allow greater movement Saddle Joints Similar to condyloid joints but allow greater movement Each articular surface has both a concave and a convex surface Example: carpometacarpal joint of the thumb Joints

Saddle Joints Figure 8.7e