Overview of Joints and Their Classifications

CHAPTER 9 1. What are joints, how are they named, and what functions do they serve? A joint (articulation) is the point where two bones meet. Joints are named based on the bones they connect and their structural or functional characteristics. Functions: They provide mobility and stability to the skeleton, allowing for body movements and supporting the body’s posture. 2. Name and describe the four major classes of joints: Bony joints (Synostosis): Immovable joints where two bones are fused together (e.g., the mandibular bones in infancy or the first rib to sternum in old age)). Fibrous joints (Synarthrosis): Joints where collagen fibers bind adjacent bones. These joints allow little to no movement (e.g., sutures, gomphoses, syndesmosis)). Cartilaginous joints (Amphiarthrosis): Joints where two bones are linked by cartilage, allowing slight movement (e.g., synchondroses and symphyses)). Synovial joints (Diarthrosis): The most structurally complex and movable joints. They contain a synovial cavity filled with fluid and are often prone to dysfunction). 3. Name some joints that become solidly fused by bone as they age: Examples include the mandibular bones, which fuse in infancy, and the first rib to the sternum, which fuses in old age). 4. Describe the three types of fibrous joints and give an example of each: Sutures: Immobile or slightly movable joints between skull bones. There are three classifications: serrate (interlocked), lap (overlapped), and plane (non-overlapped)). Gomphoses: Joints where a tooth is anchored into its socket by periodontal ligaments. There is slight movement under the stress of chewing). Syndesmoses: Joints where two bones are bound by long collagen fibers, allowing some movement (e.g., the joint between the radius and ulna or tibia and fibula)). 5. Describe the two types of cartilaginous joints and give an example of each: Synchondroses: Joints where bones are bound by hyaline cartilage, such as the epiphyseal plate in growing children or the costal cartilage of the ribs). Symphyses: Joints where bones are joined by fibrocartilage, such as the pubic symphysis and the intervertebral discs). 6. Describe the anatomy of a synovial joint and its associated structures: Articular cartilage: Hyaline cartilage that covers the facing surfaces of bones. Joint capsule: Surrounds the joint cavity, consisting of an outer fibrous capsule and an inner synovial membrane that produces synovial fluid, which lubricates the joint. Fibrocartilage pads like articular discs or menisci (e.g., in the jaw and knee) cushion and support the joint. Tendons connect muscle to bone, and ligaments connect bone to bone. Bursa: A sac of synovial fluid that reduces friction between adjacent muscles, bones, or skin). 7. Describe the six types of synovial joints: Ball-and-socket: Multiaxial joints with movement in multiple directions (e.g., shoulder, hip). Condylar (ellipsoid): Biaxial joints (e.g., wrist). Saddle: Biaxial joints (e.g., the base of the thumb). Plane (gliding): Biaxial joints (e.g., intercarpal joints). Hinge: Monoaxial joints (e.g., elbow, knee). Pivot: Monoaxial joints where a bone rotates on its axis (e.g., the atlantoaxial joint in the neck)). 8. List and demonstrate the types of movements that occur at diarthroses (synovial joints): Flexion: Decreases the joint angle. Extension: Straightens or increases the joint angle. Abduction: Moves a body part away from the midline. Adduction: Moves a body part toward the midline. Circumduction: The distal end of a limb makes a circle while the proximal end remains stationary. Rotation: Bone spins on its long axis (e.g., medial and lateral rotation). Supination: Turns the palm to face anteriorly (e.g., radius and ulna become parallel). Pronation: Turns the palm to face posteriorly (e.g., the radius crosses over the ulna)). 9. Identify the major anatomical features of the jaw, shoulder, elbow, hip, knee, and ankle joints: Jaw Joint (TMJ): A condylar, hinge, and plane joint. Ligaments: lateral ligament). Shoulder Joint: A ball-and-socket joint with ligaments like the coracohumeral and glenohumeral ligaments, and the glenoid labrum (a ring of fibrocartilage)). Elbow Joint: A hinge and pivot joint stabilized by radial collateral and ulnar collateral ligaments). Hip Joint: A ball-and-socket joint with the acetabular labrum (fibrocartilage) deepening the socket and ligaments like iliofemoral, pubofemoral, and ischiofemoral). Knee Joint: A hinge joint with medial and lateral menisci for padding, and ligaments like the anterior cruciate ligament (ACL)). Ankle Joint: A hinge joint with ligaments like the anterior talofibular, posterior talofibular, and the calcaneal (Achilles) tendon). 10. Define arthritis and describe its forms and causes: Arthritis: Inflammation of joints. It is the most common crippling disorder in the U.S. Osteoarthritis (OA): The most common form of arthritis, caused by wear-and-tear. Affects 85% of people over 70. It is characterized by crepitus, or the crunching and cracking sounds in joints. Rheumatoid Arthritis (RA): An autoimmune disease that attacks the synovial membrane, leading to ossification of the cartilage. This results in bones becoming solidly fused, a condition called ankylosis. There is no cure) Chapter 10 1. List the functions of muscular tissue and the properties it must have to carry out these functions. Functions: Movement (body parts, body contents, communication), stability (maintain posture, resist pull of gravity), control of body openings and passages, and heat production. Properties: Excitability (responsiveness): React to stimuli. Conductivity: Spread electrical impulse through muscle cell. Contractility: Shorten when stimulated. Extensibility: Can stretch without harm. Elasticity: Can recoil from stretch. 2. Describe the distinctions between the three types of muscular tissue. Skeletal Muscle: Voluntary, striated, attached to bone. Muscle cell = muscle fiber or myofiber. Cardiac Muscle: Involuntary, striated, cells = cardiomyocytes. Smooth Muscle: Involuntary, non-striated, fusiform cell shape, tapered at ends. 3. Describe the ultrastructure of a muscle fiber and its myofilaments. Muscle fiber structure includes: Sarcolemma with T-tubules (invaginations of the sarcolemma). Sarcoplasm with myofibrils, glycogen, and myoglobin. Sarcoplasmic reticulum with terminal cisterns (stores calcium for muscle contraction). Myofilaments: Thick myofilaments: Myosin with heads projecting from bundled tails. Thin myofilaments: Actin, with active sites for myosin binding, and regulatory proteins tropomyosin and troponin. 4. Explain what accounts for the striations of skeletal muscle. Striations: Narrow stripes (light and dark) that run perpendicular to the length of the cell, due to alternating bands of thick and thin filaments. 5. Describe the blood supply to a skeletal muscle. At rest, muscle receives about one-quarter of the heart’s output. During heavy exercise, muscle receives more than three-quarters of the heart’s output (a larger percentage of a larger output). Muscle is generally well-vascularized.