Joints and Muscle System Comprehensive lec Notes

Question-and-answer flashcards covering joint classification, synovial anatomy, knee ligaments, intervertebral discs, arthritis, muscle tissue structure, contraction mechanisms, muscle naming, motor units, and key muscle groups.

What are the four structural classifications of joints?

Synostosis, fibrous, cartilaginous, and synovial joints.

What is a synostosis joint and its functional classification?

A joint where two bones fuse into one; functionally classified as a synarthrosis (immovable).

What are the three functional classifications of joints?

Synarthrosis (immovable), amphiarthrosis (slightly movable), and diarthrosis (freely movable).

What defines a fibrous joint? Give an example.

Bones joined by dense connective tissue with no joint cavity; examples include sutures of the skull and the distal tibiofibular joint.

What characterizes a cartilaginous joint? Give an example.

Bones united by cartilage with no joint cavity; examples are costal cartilage joints and the pubic symphysis.

What distinguishes a synovial joint from other joint types?

Presence of a fluid-filled synovial cavity, articular cartilage, and a fibrous capsule; functionally diarthrotic (freely movable).

List the five structures common to all synovial joints.

Fibrous capsule, articular cartilage, synovial cavity, synovial fluid, and synovial membrane.

What is the function of the fibrous capsule in a synovial joint?

Encloses the joint, maintains alignment of bones, and adds mechanical strength.

What role does articular cartilage play in a synovial joint?

Provides a smooth, low-friction surface that distributes load and absorbs shock.

What is the function of synovial fluid?

Lubricates surfaces, nourishes articular cartilage, and absorbs shock.

What structure produces synovial fluid?

The synovial membrane lining the inner surface of the capsule.

What is the primary role of ligaments in synovial joints?

Reinforce the joint capsule, guide motion, and prevent excessive or abnormal movements.

How do tendons contribute to joint stability?

Anchor muscles to bone and, when under tension, help hold the joint in proper alignment.

What is a bursa and what does it do?

A small, fluid-filled sac that reduces friction between moving structures such as tendons and bone or skin and bone.

Define tendon sheath.

An elongated bursa that wraps around a tendon subjected to friction, especially in confined spaces (e.g., carpal tunnel).

What is the function of fat pads in a joint?

Cushion the joint, fill spaces created by movement, and protect articular cartilage.

What is an articular disc (meniscus) and its purpose?

Fibrocartilaginous pad inside some synovial joints that improves fit, distributes load, and increases stability.

Name the two menisci of the knee and their functions.

Medial and lateral menisci; they improve congruency between femur and tibia, absorb shock, and limit rotation.

List the major ligaments of the knee and one key function for each.

Anterior cruciate ligament (prevents anterior tibial translation); posterior cruciate ligament (prevents posterior tibial translation); medial collateral ligament (resists valgus stress); lateral collateral ligament (resists varus stress); patellar ligament (transmits quadriceps force).

Describe the structure of an intervertebral disc.

Outer annulus fibrosus of fibrocartilage surrounding an inner gel-like nucleus pulposus.

What type of joints are the intervertebral joints between vertebral bodies?

Cartilaginous symphyses—slightly movable (amphiarthroses).

Differentiate osteoarthritis, rheumatoid arthritis, and gouty arthritis.

Osteoarthritis: degenerative wear-and-tear of articular cartilage; Rheumatoid arthritis: autoimmune inflammation of synovial membrane; Gouty arthritis: deposition of uric acid crystals in joint.

What is a herniated disc?

Protrusion or rupture of the nucleus pulposus through the annulus fibrosus, often compressing spinal nerves.

How do joints that favor stability differ from those favoring mobility?

Stable joints have deep sockets, strong ligaments, and limited ROM (e.g., hip, sutures); mobile joints have shallow sockets, looser capsules, and greater ROM (e.g., shoulder).

Give an example of a joint primarily designed for stability.

The hip (coxal) joint, due to its deep acetabulum and strong ligaments.

Give an example of a joint primarily designed for mobility.

The glenohumeral (shoulder) joint, with a shallow glenoid fossa and loose capsule.

Which synovial joint structures provide shock absorption?

Articular cartilage, synovial fluid, menisci, and interposed fat pads.

What are the three types of muscle tissue and one key characteristic of each?

Skeletal (striated, voluntary), cardiac (striated, involuntary with intercalated discs), smooth (non-striated, involuntary).

Arrange the skeletal muscle hierarchy from largest to smallest.

Muscle → fascicle → muscle fiber (cell) → myofibril → myofilament (actin & myosin).

Name the connective tissue coverings of skeletal muscle components.

Epimysium (muscle), perimysium (fascicle), endomysium (muscle fiber).

Briefly explain the sliding filament theory.

Myosin heads bind to actin and pull thin filaments toward the M line, shortening sarcomeres and thus the muscle.

What are the three types of skeletal muscle fibers?

Slow oxidative (Type I), fast oxidative-glycolytic (Type IIa), and fast glycolytic (Type IIb).

List at least four criteria used in naming muscles with examples.

Size (gluteus maximus), location (temporalis), action (flexor digitorum), shape (deltoid), attachments (sternocleidomastoid).

Differentiate the tendon of origin from the tendon of insertion.

Origin attaches to the relatively fixed bone; insertion attaches to the bone that moves during contraction.

What are the main components of a neuromuscular junction?

Axon terminal with synaptic vesicles, synaptic cleft, and the motor end plate on the muscle fiber with ACh receptors.

Define a motor unit.

A single motor neuron and all the muscle fibers it innervates.

How does differential recruitment of motor units affect muscle force?

Activating more and/or larger motor units increases force; selective recruitment enables fine vs. powerful movements.

Name the four muscles of the rotator cuff.

Supraspinatus, infraspinatus, teres minor, and subscapularis (SITS).

List the muscles of the quadriceps femoris group.

Rectus femoris, vastus lateralis, vastus medialis, vastus intermedius (and sometimes articularis genus).

List the muscles of the hamstring group.

Biceps femoris, semitendinosus, and semimembranosus.

Define agonist, antagonist, and synergist with examples.

Agonist: prime mover (biceps brachii during elbow flexion); antagonist: opposes movement (triceps brachii); synergist: assists/makes motion more efficient (brachialis).

How does fascicle arrangement influence muscle force versus mobility?

Parallel/longitudinal fascicles favor range of motion; pennate or convergent fascicles favor greater force production.

How do muscles, bones, connective tissue, nerves, and joints cooperate to produce movement?

Motor neurons stimulate muscles → muscles contract and pull via tendons on bones across joints → joint structure guides motion while CT stabilizes → coordinated action yields body movement.