BIOL251 Exam 2(Chapter 8)

"Arthro-" or "Arthr-"

Prefix meaning joint.

Joint

Articulations, the site where two bones meet. May or may not allow for movement (some joints allow no movement at all). Shape determines relative motion.

General functions of joints

Mobility and stability.

Mobility function of joints

Allows movement of various body parts. Different types of joints allow for different amounts and types of movement due to shape differences.

Stability function of joints

Holds the skeleton together and prevents damage to internal structures (soft tissues). Mostly the joints that don't move at all, bones locked in place.

General classifications of joints

Structural and functional.

Structural classification of joints

Type of tissue that connects bones at articulating surface. Joint cavity may or may not be present.

Functional classification of joints

Amount of movement allowed by the joint.

Types of structural classification of joints

Fibrous joints, cartilaginous joints, synovial joints.

Fibrous joints

Joints composed of extremely short collagen fibers of connective tissue with no joint cavity present. Mostly synarthroses, few amphiarthroses.

Specific types of fibrous joints

1. Sutures; 2. Syndesmoses; 3. Gomphoses.

Sutures

Composed of thick bundles of extremely strong and short collagen fibers, permitting very little movement. Found between the bones of the skull, helps protect brain and prevent injury to the skull.

Syndesmoses

Bones are connected to one another only by ligaments. Movement allowed by the joint depends on length of ligament bands (e.g., interosseous membrane between radius/ulna and tibia/fibula).

Ligaments

Bands of fibrous tissue that join bone to bone.

Relationship between length and movement allowed in ligaments

Longer fibers allow for more range of motion.

Gomphoses

Only joint type that does not join bone to another bone; joins tooth to alveolar socket in jaw bone. Fibers are very short, providing very limited movement.

Periodontal ligament

Joins the bone of the mandible/maxilla to the tooth.

Cartilaginous joints

Bones joined by cartilage with no joint cavity. Either synarthroses or amphiarthroses.

Specific types of cartilaginous joints

Synchondroses and symphyses.

Synchondroses

Bones united with a plate of hyaline cartilage, mostly synarthroses (e.g., costal cartilage to help maintain shape of the ribcage and prevent ribs from poking).

Symphyses

Fibrocartilage joins bone, allowing some limited movement. Extremely resilient, very good for shock absorption due to fibrocartilage (e.g., intervertebral joints, pubic symphysis).

Synovial joints

Possess a joint cavity and are classified as diarthroses. Most joints in body fall under this classification, found in appendicular skeleton.

Six structures found in all synovial joints

1. Articular cartilage; 2. Joint cavity; 3. Articular capsule; 4. Synovial fluid; 5. Reinforcing ligaments; 6. Innervation and vascularization.

Articular cartilage

Hyaline cartilage covering bone ends.

Joint cavity

Small space between articulating bones.

Primary function of the joint cavity

Completely enclosed space, holds fluid to allow movement of bones relative to one another.

Articular capsule

Two-layered capsule that encloses the joint cavity.

Two layers of articular capsule

Fibrous layer and synovial membrane.

Fibrous layer of articular capsule

Outer layer of the articular capsule that is continuous with the periosteum of bones. Connects bones that articulate, prevents them from being easily pulled apart.

Synovial membrane

Inner layer of the articular capsule that lines joint cavity. Not found where there is articular cartilage. Cells here produce and secrete fluid that fills joint cavity.

Diarthroses

Joints that allow free movement, mostly found in appendicular skeleton.

Amphiarthroses

Joints that allow limited movement, mostly found in axial skeleton.

Synarthroses

Joints that allow no movement, mostly found in axial skeleton.

Synovial fluid

Slippery fluid occupying space in joint capsule and articular cartilages. Prevents bone rubbing on one another, protects articular cartilage.

Synovial fluid state when joint is not active

Fluid is viscous and stored in articular cartilage.

Function of synovial fluid when joint is active

Fluid thins and becomes watery, fills up joint cavity.

Reinforcing ligaments

Bandlike ligaments that join articulating bones. Allows stretching (6-10%), reinforces joint, holds bone in place.

Innervation to synovial joints

Joints supplied with sensory nerve fibers. Mechanoreceptors detect pressure and stretch; nociceptors detect pain.

Vascularization of synovial joints

Rich blood supply to joints. Keeps cartilage healthy, synovial fluid gets produced by raw materials from blood supply.

Structures optionally associated with synovial joints

Bursae and tendon sheaths.

Bursae

Flattened sacs that contain a small amount of synovial fluid. Found in synovial joints where structures would otherwise rub up against each other to reduce friction.

Tendon sheath

Elongated bursa that wraps completely around a tendon subjected to frequent friction so tendons can roll around other structures (e.g., wrists and ankles).

Function of tendon sheaths

Prevents excessive friction for a particular tendon.

Drawback of high joint mobility

The more mobile a joint is, the less stable it is; runs the risk of dislocation.

Factors influencing joint stability

Articular surfaces, ligaments, muscle tone (always need at least 2 of these 3).

Articular surfaces factor in stability

How well the bones fit together influences stability (e.g., hip joint fits tightly and is very stable; GH joint fits loosely and is quite unstable).

Ligaments factor in stability

The more ligaments, the stronger the joint (exception occurs when they are overstretched).

Muscle tone factor in stability

Tendons attach muscle to bone and wrap around/over joints to brace them. Muscle is always slightly contracted even at rest, constantly pulling on tendon.

Most important joint stability factor

Muscle tone.

Movements allowed by synovial joints

Nonaxial, uniaxial, biaxial, multiaxial.

Nonaxial movement

No axis around which movement can take place; bones have flat surfaces allowing gliding movements (plane joints like intercarpal and intertarsal joints).

Uniaxial movement

Allows movement around a single axis (flexion/extension or rotation). Shapes: hinge joint (e.g., between humerus and ulna) and pivot joint (e.g., between radius and ulna).

Biaxial movement

Allows movement around two axes (flexion/extension and adduction/abduction). Shapes: condylar joint (e.g., knuckle of finger) and saddle joint (e.g., base of thumb).

Multiaxial movement

Allows movement around multiple axes (flexion/extension, abduction/adduction, and rotation). Shape: ball-and-socket joint (e.g., shoulder and hip joints).

Specific examples of synovial joints

Temporomandibular (jaw), glenohumeral (shoulder), coxal (hip), knee.

Temporomandibular joint (TMJ)

Where the mandible articulates to the temporal bone; modified hinge joint. Articular disc divides synovial cavity into superior (allows lateral excursion) and inferior (allows elevation/depression) portions.

Glenohumeral (shoulder) joint

Where the humerus articulates with the scapula; most freely moving joint in the body.

Stability of the GH joint

Reinforcing ligaments (thin and loose), rotator cuff, and glenoid labrum.

Reinforcing ligaments of the GH joint

Coracohumeral ligament and glenohumeral ligaments.

Coracohumeral ligament

Ligament located on the posterior aspect of the shoulder.

Glenohumeral ligament

Ligament located on the anterior aspect of the shoulder.

Rotator cuff

Four muscles and their tendons encircling the shoulder joint to provide stability; easily damaged.

Glenoid labrum

Rim of fibrocartilage around the glenoid fossa.

How the glenoid labrum increases stability

Deepens the glenoid fossa socket to hold the head of the humerus in place.

Elbow joint

Where the humerus articulates with the ulna.

Stability of the elbow joint

1. Close fit of trochlea on humerus and trochlear notch on ulna; 2. Muscle and tendon wrapping around elbow; 3. Ulnar and radial collateral ligaments preventing lateral movement.

Ulnar collateral ligament

Medial side elbow ligament.

Radial collateral ligament

Lateral side elbow ligament.

Coxal joint

Where the head of the femur articulates with the os coxa.

Stability of the coxal joint

Provided by articular surfaces and strong ligaments, including the acetabular labrum.

Acetabular labrum

Holds head of femur to further deepen socket of hip joint.

Ligaments of articular capsule of hip

Iliofemoral, pubofemoral, and ischiofemoral ligaments; twist tightly over each other when standing up for added stability.

Ligamentum teres

Ligament of the head of the femur containing blood vessels and nerve supply, assisting in sensory signaling and red bone marrow production.

Knee joint

A single joint cavity shared by three separate joints, reinforced by muscles, tendons, and several ligaments.

Femoropatellar joint

Joint located between the patella and femur.

Tibiofemoral joints

Joints between tibia and femur (one medial and one lateral).

Important stabilizing structures in the knee joint

Menisci, extracapsular and capsular ligaments, and intracapsular ligaments.

Menisci

Thin layer of fibrous cartilage at outer margins of tibiofemoral joints that forms ridges along the outer margins of the joint.

Extracapsular and capsular knee ligaments

Prevent hyperextension of the knee.

Intracapsular knee ligaments

Cruciate ligaments that secure articulating bones, preventing displacement and hyperextension of the knee.

Anterior cruciate ligament (ACL)

Prevents forward sliding of the tibia and attaches to the anterior portion of the tibia.

Posterior cruciate ligament (PCL)

Prevents backward sliding of the tibia and forward sliding of the femur, attaching to the posterior portion of the tibia.

Arthritis

Inflammatory or degenerative disease affecting joints; the most widespread crippling disease in North America.

Inflammatory arthritis

Swelling of joint tissue full of excess fluid, pressing up against other structures.

Degenerative arthritis

Permanent loss of joint tissue over time.

Acute arthritis

Forms include bacterial and inflammatory types that are easily treated with antibiotics.

Chronic arthritis

Long-lasting inflammatory or degenerative forms of arthritis.

Types of arthritis

Osteoarthritis and rheumatoid arthritis.

Osteoarthritis (OA)

Most common form of chronic arthritis; progresses slowly and is irreversible.

Factors increasing the likelihood of developing osteoarthritis

Being female and ages 60 or higher.

Cause of osteoarthritis

More articular cartilage is being destroyed than is replaced.

Effect of osteoarthritis

Exposed bone rubs together forming bone spurs; bone ends deform, restricting joint movement.

Rheumatoid arthritis (RA)

An autoimmune chronic inflammatory disorder that is bilateral and degenerative, with flare-ups followed by periods of remission.

Progression of RA

1. Synovial membrane becomes inflamed; 2. Lymphocytes and macrophages flood area destroy cause of inflamation and macrophages also destroy some of the synovial membrane 3. Synovial fluid accumulates and a pannus forms.

Pannus

A thickening of the synovial membrane that breaks down cartilage tissue over time.

Ankylosis

Occurs due to cartilage destruction, leading to bones fusing together where cartilage or joints used to be.