Musculoskeletal Anatomy - Joints for Movement PDF

MUSCULOSKELETAL ANATOMY Joints for Movement  Foundations of Movement  The musculoskeletal system includes bones, joints, skeletal muscles, tendons, and ligaments.  Muscles generate force; tendons transfer it to bones; and the bones move if enough force is transmitted.  The f...

MUSCULOSKELETAL ANATOMY Joints for Movement  Foundations of Movement  The musculoskeletal system includes bones, joints, skeletal muscles, tendons, and ligaments.  Muscles generate force; tendons transfer it to bones; and the bones move if enough force is transmitted.  The force must be enough to overcome the weight of the moving body part, gravity, and other external resistance.  Motion occurs at joints associated with one or both ends of the bone.  The point at which two or more bones meet is called a joint, or articulation. Joints are responsible for movement, such as the movement of limbs, and stability, such as the stability found in the bones of the skull.  Classification of Joints on the Basis of Structure  There are two ways to classify joints:  on the basis of their structure  on the basis of their function.  The structural classification divides joints into  bony, fibrous,  cartilaginous,  synovial joints  depending on the material composing the joint and the presence or absence of a cavity in the joint. Fibrous Joints  The bones of fibrous joints are held together by fibrous connective tissue.  There is no cavity, or space, present between the bones  Most fibrous joints do not move at all  Or only capable of minor movements.  There are three types of fibrous joints:  sutures, syndesmoses, and gomphoses.  Sutures are found only in the skull and possess short fibers of connective tissue that hold the skull bones tightly in place Fibrous Joints (cont’)  Syndesmoses are joints in which the bones are connected by a band of connective tissue, allowing for more movement than in a suture. An example of a syndesmosis is the joint of the tibia and fibula in the ankle. The amount of movement in these types of joints is determined by the length of the connective tissue fibers.  Gomphoses occur between teeth and their sockets; the term refers to the way the tooth fits into the socket like a peg. The tooth is connected to the socket by a connective tissue referred to as the periodontal ligament.  Cartilaginous joints are joints in Cartilagino which the bones are connected by us Joints cartilage. In a synchondrosis, the bones are joined by hyaline cartilage and are found in the epiphyseal plates of growing bones in children. In symphyses, hyaline cartilage covers the end of the bone but the connection between bones occurs through fibrocartilage and are found at the joints between vertebrae. Either type of cartilaginous joint allows for very little movement. Synovial Joints  The only joints that have a space between the adjoining bones  This space is referred to as the synovial (or joint) cavity  filled with synovial fluid.  Synovial fluid lubricates the joint,  reducing friction between the bones and  allowing for greater movement. Synovial Joints (con’t)  The ends of the bones are covered with hyaline articular cartilage  the entire joint is surrounded by an articular capsule  composed of connective tissue that allows movement of the joint  while resisting dislocation.  Articular capsules may also possess ligaments that hold the bones together.  Synovial joints are capable of the greatest movement of the three structural joint types;  the more mobile a joint, the weaker the joint.  Knees, elbows, and shoulders are examples of synovial joints. Classification of Joints on the Basis of Function The functional A synarthrosis is a classification divides joint that is joints into three immovable. This categories: includes sutures, synarthroses, gomphoses, and amphiarthroses, and synchondroses. diarthroses. Amphiarthroses are Diarthroses are joints that allow slight joints that allow for movement, including free movement of the syndesmoses and joint, as in synovial symphyses. joints. Movement at Synovial Joints  The wide range of movement allowed by synovial joints produces different types of movements.  The movement of synovial joints can be classified as one of four different types:  gliding,  angular,  rotational, or  special movement. Gliding Movement  Occur as relatively flat bone surfaces move past each other.  Gliding movements produce very little rotation or angular movement  The joints of the carpal and tarsal bones are examples of joints that produce gliding movements.  Produced when the angle between the bones of a joint changes.  Several different types of angular Angular movements, flexion, extension, movements hyperextension, abduction, adduction, and circumduction.  Different Types of Angular Movements  Flexion, or bending, occurs when the angle between the bones decreases. Moving the forearm upward at the elbow or moving the wrist to move the hand toward the forearm are examples of flexion.  Extension is the opposite of flexion in that the angle between the bones of a joint increases. Straightening a limb after flexion is an example of extension.  Hyperextension is extension past the regular anatomical position This includes moving the neck back to look upward or bending the wrist so that the hand moves away from the forearm. Different Types of Angular Movements  Abduction occurs when a bone moves away from the midline of the body.  Examples of abduction are moving the arms or legs laterally to lift them straight out to the side.  Adduction is the movement of a bone toward the midline of the body.  Movement of the limbs inward after abduction is an example of adduction.  Circumduction is the movement of a limb in a circular motion,  Moving the arm in a circular motion. Rotational movement  the movement of a bone as it rotates around Rotational its longitudinal axis. Movement  Rotation can be toward the midline of the body (medial rotation)  Away from the midline (lateral rotation)  Movement of the head from side to side is an example of rotation.  Special Movements  Some movements that cannot be classified as gliding, angular, or rotational are called special movements.  Inversion involves the soles of the feet moving inward, toward the midline of the body.  Eversion is the opposite of inversion, movement of the sole of the foot outward, away from the midline of the body.  Protraction is the anterior movement of a bone in the horizontal plane.  Retraction occurs as a joint moves back into position after protraction. Protraction and retraction can be seen in the movement of the mandible as the jaw is thrust outwards and then back inwards.  Special Movements (cont’)  Elevation is the movement of a bone upward, such as when the shoulders are shrugged, lifting the scapulae.  Depression is the opposite of elevation—movement downward of a bone, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position.  Dorsiflexion is a bending at the ankle such that the toes are lifted toward the knee.  Plantar flexion is a bending at the ankle when the heel is lifted, such as when standing on the toes.  Supination is the movement of the radius and ulna bones of the forearm so that the palm faces forward.  Pronation is the opposite movement, in which the palm faces backward.  Opposition is the movement of the thumb toward the fingers of the same hand, making it possible to grasp and hold objects. Types of Synovial Joints  Different types of joints allow different types of movement.  Planar,  Hinge,  Pivot,  Condyloid,  Saddle, and  Ball-and-socket Joints and Skeletal Movement Planar Joints  Planar joints have bones with articulating surfaces that are flat or slightly curved faces.  These joints allow for gliding movements, and so the joints are sometimes referred to as gliding joints.  The range of motion is limited in these joints and does not involve rotation.  Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae Hinge Joints  In hinge joints, the slightly rounded end of one bone fits into the slightly hollow end of the other bone.  In this way, one bone moves while the other remains stationary, like the hinge of a door.  The elbow is an example of a hinge joint.  The knee is sometimes classified as a modified hinge joint Pivot Joints  Pivot Joints consist of the rounded end of one bone fitting into a ring formed by the other bone.  This structure allows rotational movement, as the rounded bone moves around its own axis.  An example of a pivot joint is the joint of the first and second vertebrae of the neck that allows the head to move back and forth.  The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint. Condyloid Joints  Condyloid Joints consist of an oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone.  This is also sometimes called an ellipsoidal joint.  This type of joint allows angular movement along two axes, as seen in the joints of the wrist and fingers, which can move both side to side and up and down.  Saddle Joints  The ends of each bone resemble a saddle, with concave and convex portions that fit together.  Saddle joints allow angular movements similar to condyloid joints but with a greater range of motion.  An example of a saddle joint is the thumb joint, which can move back and forth and up and down, but more freely than the wrist or fingers.  Ball-and-socket Joints  Ball-and-socket joints possess a rounded, ball-like end of one bone fitting into a cuplike socket of another bone.  This organization allows the greatest range of motion, as all movement types are possible in all directions.  Examples of ball-and-socket joints are the shoulder and hip joints. THE END !!