Lecture 2



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 _______________

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