Chapter 8 Joints anatomy exam 2

What is an articulation (joint), and what are its two primary functional roles in the skeletal system?

An articulation is a site where two or more bones meet; its two primary functional roles are to provide mobility (allowing movement of body parts) and stability (holding the skeleton together).

How do the structural and functional classification systems of joints differ in criteria?

Structural classification is based on the type of connective tissue joining the articulating bones and whether a joint cavity is present (Fibrous, Cartilaginous, Synovial); Functional classification is based on the amount of movement allowed at the joint (Synarthroses, Amphiarthroses, Diarthroses).

What are the definitions of synarthroses, amphiarthroses, and diarthroses?

Synarthroses are immovable joints; Amphiarthroses are slightly movable (limited movement) joints; Diarthroses are freely movable joints.

What structural characteristics define fibrous joints, and what functional movement classification do most fibrous joints fall under?

Fibrous joints are joined by short collagen fibers of connective tissue and lack a joint cavity; functionally, most fibrous joints are synarthroses (immovable), with a few classified as amphiarthroses.

How do the 3 types of fibrous joints (sutures, syndesmoses, gomphoses) differ in location and structure?

Sutures are rigid joints between skull bones united by very short collagen fibers; Syndesmoses are bones connected exclusively by ligaments (fibrous bands); Gomphoses are "peg-in-socket" fibrous joints securing teeth into alveolar jaw sockets via the periodontal ligament.

What structural characteristics define cartilaginous joints, and what are the 2 specific types?

Cartilaginous joints unite articulating bones with cartilage and lack a joint cavity; the two types are synchondroses (hyaline cartilage) and symphyses (fibrocartilage).

How do synchondroses and symphyses differ in cartilage type and functional mobility?

Synchondroses are united by hyaline cartilage and are functionally synarthroses (immovable; e.g., epiphyseal plates, 1st rib to sternum); Symphyses are united by fibrocartilage and are functionally amphiarthroses (slightly movable; designed to resist compression and absorb shock; e.g., intervertebral discs, pubic symphysis).

What structural characteristics define synovial joints, where are they mostly located, and what is their functional movement classification?

Synovial joints contain a fluid-filled joint cavity separating the articulating bones; they are functionally classified as diarthroses (freely movable) and are mostly found in the appendicular skeleton.

What are the 6 structural features present in ALL synovial joints?

1) Articular cartilage (hyaline cartilage covering bone ends), 2) Joint cavity (small fluid-filled space), 3) Articular capsule (outer fibrous layer + inner synovial membrane), 4) Synovial fluid (slippery lubricating fluid), 5) Reinforcing ligaments (bands binding bone to bone), 6) Innervation & Vascularization (rich supply of sensory nerves and blood capillaries).

What are the two distinct layers of the articular capsule in a synovial joint, and what are their functions?

Outer Fibrous Layer is dense irregular connective tissue continuous with the periosteum that strengthens the joint; Inner Synovial Membrane is loose connective tissue lining the inner capsule that produces synovial fluid.

What is the physical behavior of synovial fluid when a joint is at rest versus when it is active?

When the joint is at rest, synovial fluid is thick and viscous; when the joint becomes active, the fluid thins and becomes watery, spreading across articular surfaces to reduce friction and nourish chondrocytes.

How do bursae and tendon sheaths differ in structure, and what is their shared physiological function?

Bursae are flattened fibrous sacs lined with synovial membrane containing a thin film of synovial fluid; Tendon Sheaths are elongated bursae that wrap completely around a tendon subjected to frequent friction; both function to reduce friction between adjacent structures during movement.

What 3 factors influence the stability of a synovial joint, and which factor is the MOST important?

1) Shape of articular surfaces, 2) Number and positioning of reinforcing ligaments, 3) Muscle tone (tendons crossing the joint); Muscle tone is the most important factor in maintaining joint stability.

What is the relationship between joint mobility and joint stability?

They have an inverse relationship: the more mobile a joint is, the less stable it is (and vice versa).

What defines nonaxial movement in a synovial joint, what movement occurs, and what joint shape corresponds to it?

Nonaxial movement occurs without axis rotation over flat articulating surfaces, allowing gliding movements; it corresponds to a plane joint.

What defines uniaxial movement, what movements are permitted, and what 2 joint shapes are uniaxial?

Uniaxial movement occurs around a single axis, permitting flexion/extension OR rotation; the two shapes are hinge joints and pivot joints.

What defines biaxial movement, what movements are permitted, and what 2 joint shapes are biaxial?

Biaxial movement occurs around two axes, permitting flexion/extension AND adduction/abduction; the two shapes are condylar joints and saddle joints.

What defines multiaxial movement, what movements are permitted, and what joint shape is multiaxial?

Multiaxial movement occurs around three or more axes, permitting flexion/extension, abduction/adduction, AND rotation; the joint shape is a ball-and-socket joint.

What structural type of joint is the temporomandibular joint (TMJ), and how does its articular disc divide its movement?

The TMJ is a modified hinge joint; its articular disc divides the joint cavity into a superior compartment (allows lateral excursion / side-to-side grinding) and an inferior compartment (allows elevation and depression / hinge opening and closing).

Why is the glenohumeral (shoulder) joint the most freely moving joint in the body, and what 3 structures provide its stability?

It has a shallow socket and thin, loose capsule; stability is provided by 1) Rotator cuff tendons, 2) Glenoid labrum (fibrocartilage rim deepening the glenoid cavity), and 3) Coracohumeral and glenohumeral ligaments.

What structural features give the elbow joint its strong mechanical stability?

1) Close interlocking fit between the trochlea of the humerus and the trochlear notch of the ulna, 2) Strong side-to-side reinforcing ligaments (ulnar collateral and radial collateral ligaments), and 3) Biceps and triceps tendons wrapping over the joint.

What structural features contribute to the exceptional stability of the coxal (hip) joint?

1) Deep socket of the acetabulum enhanced by a fibrocartilage acetabular labrum, 2) Strong spiraling capsular ligaments (iliofemoral, pubofemoral, ischiofemoral ligaments), and 3) Ligamentum teres (ligament of the head of the femur).

What 3 individual joints are enclosed within the single joint cavity of the knee joint?

1) Femoropatellar joint (between patella and distal femur), 2) Medial tibiofemoral joint (between medial condyles of femur and tibia), and 3) Lateral tibiofemoral joint (between lateral condyles of femur and tibia).

What are the menisci of the knee joint, what is their tissue composition, and what is their primary function?

C-shaped rings of fibrocartilage located on the outer margins of the tibial condyles that deepen the articular surface, absorb shock, and prevent side-to-side rocking of the femur on the tibia.

How do the Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL) differ in attachment and function in the knee?

ACL attaches to the anterior tibia and prevents forward sliding of the tibia and backward displacement of the femur (prevents hyperextension); PCL attaches to the posterior tibia and prevents backward sliding of the tibia and forward displacement of the femur.

What is Osteoarthritis (OA), what causes it, and what structural changes occur in the joint?

The most common chronic, degenerative form of arthritis ("wear-and-tear"), caused by articular cartilage being destroyed faster than it is replaced; exposed bone ends rub together, thicken, and form sharp bone spurs (osteophytes), restricting movement.

What is Rheumatoid Arthritis (RA), and how does it develop in the body?

A chronic, autoimmune inflammatory disorder that typically affects joints bilaterally (symmetrical); the body's immune system attacks its own synovial membranes, causing severe inflammation, joint destruction, flare-ups, and remissions.

What is a pannus in Rheumatoid Arthritis, and how does it lead to ankylosis?

A pannus is an abnormal, thickened mass of inflamed synovial tissue that secretes enzymes eroding articular cartilage; as cartilage is destroyed, scar tissue forms and calcifies, causing ankylosis (complete fusion of articulating bones, immobilizing the joint).