Outline 6
Joints
Joints and their Classification – Joints are classified according to the manner in which the adjacent bones are ______to each other
· ______Joint (also called synostosis)
o Immovable joint formed when the gap between two bones ossifies and the bones become, in effect, a single bone
§ An infant is born with right and left mandibular bones and ______bones, but these fuse into a single mandible and frontal bone
· Fibrous Joint (also called synarthrosis)
o It is a point at which adjacent bones are bound by ______fibers that emerge from the matrix of one bone, cross the space between them, and penetrate into the matrix of the other bone
o Three kinds of fibrous joints
§ Sutures –
· ______sutures – appear as wavy lines along the adjoining bones, firmly interlocking them
o Example: Sagittal suture
· ______sutures (squamous sutures) – occur where two flat bones have overlapping edges
o Example: squamous suture
· ______sutures – occur where two bones have straight, non-overlapping edges
o Example: suture between right and left palatine processes of the maxilla
§ Gomphoses –
· The attachment of a tooth to its socket
o The tooth is held in place by a periodontal ______
§ The ligament allows the tooth to move a little under the stress of chewing
§ Syndesmoses –
· Fibrous joints in which the bones are bound by longer collagenous fibers than in a suture or gomphosis, giving the bones more mobility
o Example: the shafts of the ulna and radius are connected by an interosseous membrane which allows the forearm to ______
· Cartilaginous Joint (also called amphiarthroses)
o Bones are linked by ______
o Kinds of cartilaginous joints:
§ Synchondroses – joints in which the bones are bound by hyaline cartilage
· Example 1: temporary joint between the epiphysis and diaphysis of a long bone in a child, formed by the ______plate
· Example 2: Attachment of a rib to the sternum by a hyaline costal cartilage
§ Symphyses – joints in which bones are joined by fibrocartilage
· Example 1: pubic symphysis that connects the right and left ______bones
· Example 2: cartilage between the bodies of two vertebrae
Synovial Joints (also called diarthroses) – freely movable joints
· General Anatomy
o Articular cartilage – a thin layer of ______cartilage covering the connecting surface of a bone at a synovial joint, serving to reduce friction and ease joint movement
o Joint cavity – narrow space between the ______in a synovial joint
o Synovial fluid – a lubricating fluid similar to eggwhite in consistency, found in the synovial joint cavities and bursae
o Joint capsule – capsule of connective tissue that encloses the joint cavity and retains fluid
§ Fibrous capsule – outer portion of the joint capsule ______with the periosteum of the bones
§ Synovial membrane – inner portion with fibroblast-like cells that secrete ______fluid and macrophages that remove debris from the joint cavity
o Articular disc – fibrocartilage that grows inward from the joint capsule to form a pad between the articular bones
o Meniscus – crescent-shaped cartilages in the knee that absorb shock and guide bones across each other
o Tendon – a collagenous band or cord associated with a muscle, usually attaching it to a ______and transferring muscular tension to it
o Ligament – a cord or band of tough collagenous tissue binding one organ to another, especially one bone to another, and serving to hold organs in place
o Bursa – a sac filled with synovial fluid at a synovial joint, serving to facilitate muscle or joint action
o Tendon sheath – bursae that are elongated cylinders wrapped around a ______
o Bursitis – Inflammation of a bursae, usually due to overexertions of a joint
o Tendinitis – inflammation of a tendon ______
· Types of Synovial Joints
o Hinge joint – joints that can move only in one plane, like a door hinge
§ One bone has a convex surface that fits into a concave depression of the other
§ Examples: ______, knee, interphalangeal joints (within finger or toe)
o Gliding joint – joints that slide over each other with limited twisting
§ Articular surfaces are flat or only slightly concave and convex
§ Examples: ______and ankle bones, sternoclavicular joint
o ______joint – joints in which the first bone rotates on its longitudinal axis relative to the other
§ Example 1: the atlas bone rotates on the dens of the axis bone, so the head can rotate to gesture “no”
§ Example 2: a ligament on the ulna wraps around the head of the radius, which allows the radius to rotate as the forearm is turned
o Saddle joint – joints that allow movement in two axes (providing a wide range of movement)
§ the articular surface of each bone is shaped like a ______(concave in one direction and convex in the other)
§ Example: attachment of the thumb to the hand
o Condyloid joint – joints that allow movement in two axes (but more limited than in the saddle joint)
§ The articular surface of one bone is oval and convex, while the other bone is a similarly shaped depression
§ Example: attachment of the index finger to the hand (metacarpophalangeal joint)
o Ball-and-socket joint – joints that provide the greatest range of movement (they are multiaxial)
§ A smooth hemispherical head of one bone fits into a cuplike depression on another
§ Examples: humerus into ______, femur into os coxae
· Movement of Synovial Joints
o Flexion – movement that decreases the angle of a joint on an anterior-posterior plane
§ Examples: bending the elbow or knee, bending the neck to look down at the floor
o Extension – movement that ______a joint and generally returns a body part to anatomical position
§ Examples: straightening the elbow or knee, raising the head to look directly forward
o ______extension – extension of a joint beyond 180O.
§ Examples: raising the back of your hand “as if admiring a new ring” or bending the neck to look upward
o Abduction – movement of a body part ______the median plane
§ Examples: raising the arm to one side of the body, or moving the feet away from each other while standing; also spreading the ______apart on one hand
o Adduction – movement of a body part toward the median plane
§ Examples: bringing the arms to the sides or sliding the feet closer together while standing; also putting the fingers close together on one hand
o Elevation – movement of a body part to ______it vertically
§ Example: shrugging the shoulders to raise the scapulae and clavicles
o Depression – movement of a body part downward
§ Example: lowering the shoulders
o Protraction – movement of a body part ______on plane parallel with the ground
§ Example: moving the mandible forward, or moving the shoulders forward
o Retraction – movement of a body part posteriorly on a plane parallel with the ground
§ Example: moving the mandible ______, or moving the shoulders backward
o Lateral excursion – sideways movement to the right or left
§ Example: movement of the jaw away from midline
o Medial excursion – movement back to midline
§ Example: movement of the jaw back to midline
o Circumduction – movement in which one end of an appendage remains relatively stationary while the other end makes a circular motion
§ Example – winding up for a pitch in baseball, making “big arm circles” in gym class
o Rotation - movement in which a bone turns on its ______axis
§ Examples: twisting the thigh at the femur to os coxae joint, or twisting the arm at the glenohumeral joint.
o Supination – movement of the forearm so that the palm faces forward or upward
o Pronation – movement of the forearm so that the palm faces ______or downward
o Opposition – movement of the thumb to approach or touch the ______
o Reposition – movement of the thumb to anatomical position, parallel to the index finger
o Dorsiflexion – movement in which the toes are raised
o Plantar flexion – movement in which the toes are pointed ______
o Inversion – movement that lifts the medial border of the foot to turn the soles of the feet medially (inward)
o Eversion – movement that lifts the lateral border of the foot to turn the soles of the foot away from each other
· Range of Motion
o Structure and action of the muscles
§ Tendons, ligaments, and muscles have proprioceptors that monitor joint angle and muscle tension.
§ When the ______receives this information, it sends signals back to the muscles to increase or decrease their state of contraction
§ This adjusts the position of the joint and the tautness of tendons
o Structure of the articular surfaces of the ______
§ Some joints cannot be hyperextended
· The olecranon of the ulna fits into the olecranon fossa of the humerus, and prevents further movement in that direction
o Strength and tautness of ______, tendons, and joint capsule
§ The knee cannot be hyperextended because its cruciate ligament is pulled tight as the knee is extended
Anatomy of Selected Synovial Joints
· The Jaw Joint
o Type: condyloid, hinge, and gliding
o Movements: elevation, depression, protraction, retraction, excursion
· The Shoulder Joint
o Type: ball-and-socket
o Movements: adduction, abduction, flexion, ______, circumduction, medial and lateral rotation
· The Elbow Joint
o Type: hinge and pivot
o Movements: flexion, extension, pronation, supination, ______
· The Hip (Coxal) Joint
o Type: ball-and-socket
o Movements: adduction, abduction, ______, extension, circumduction, medial and lateral rotation
· The Knee Joint
o Type: primarily hinge
o Movements: flexion, extension, slight rotation
· The Ankle Joint
o Type: hinge
o Movements: dorsiflexion, plantar flexion, extension
Clinical Perspectives
· ______– inflammation of a joint
o Osteoarthritis (wear-and-tear arthritis)
§ As joints age, the articular cartilage softens and degenerates
§ As cartilage becomes roughened by wear, joint movement may be accompanied by crunching or crackling sounds
§ As the articular cartilage wears away, exposed bone tissue often develops ______that grow into the cavity, restricting movement and causing pain
o Rheumatoid arthritis
§ Results from autoimmune attack against the joint tissues
§ Misguided antibodies attack the synovial membrane.
§ Inflammatory cells accumulate in the synovial fluid and produce enzymes that degrade the articular cartilage
§ The synovial membrane thickens, fluid accumulates in the capsule, and the capsule is invaded by fibrous connective tissue
§ As the cartilage degenerates, the bones become solidly ______