Skeletal and Muscular Systems: Bone Remodeling, Joints, and Muscle Physiology

Comprehensive vocabulary flashcards covering bone remodeling, fracture repair, joint classifications and motions, synovial joint varieties, and muscular anatomy and physiology.

Osteocytes

Cells that release chemical signals to send osteoclasts to the site of bone damage during bone remodeling.

Osteoclasts

Cells that release enzymes allowing $Ca_3(PO_4)_2$ to be digested so that calcium and phosphate are resorbed into the blood.

Reduction and Immobilization

Key clinical interventions required for treating bone fractures.

Fibrocartilaginous Callus

A temporary structure that forms to connect broken bone ends after a hematoma forms and before osteoblasts replace it with spongy bone.

Synarthrosis

A functional classification for a non-moving joint that provides maximum stability (such as joints in the cranium).

Amphiarthrosis

A functional classification for a slightly-moving joint that provides good stability (such as where pubic bones meet in the pelvis).

Diathrosis

A functional classification for a freely moving joint that provides the least stability (such as knee and elbow joints).

Gliding

Movement occurring when one flat bone surface glides or slips over another in a back-and-forth or side-to-side direction.

Flexion

A bending movement that decreases the angle of the joint so that articulating bones get closer together.

Extension

A bending movement that increases the angle of the joint.

Hyperextension

Bending that extends beyond the standard anatomical position.

Rotation

The turning of a bone around its own long bone axis.

Supination

A movement described as turning or twisting forward.

Pronation

A movement described as turning or twisting backward.

Abduction

Moving a limb away from the median plane.

Adduction

Moving a limb toward the median plane.

Opposition

The action of touching the thumb to each fingertip.

Circumduction

The movement of a limb in a circle.

Elevation and Depression

Lifting a body part superiorly, followed by lowering it back down.

Protraction and Retraction

Non-angular anterior and posterior movements of a body part.

Dorsiflexion

Bending the foot at the ankle upwards towards the body.

Plantar Flexion

Bending the foot at the ankle downwards and away from the body.

Inversion and Eversion

Moving the foot medially (inversion) and moving the foot laterally (eversion).

Fibrous Joints

A structural classification of joints where bones are connected by collagen fibers, rendering them mostly immovable.

Cartilaginous Joints

A structural classification of joints where bones are united by cartilage, making them rigid but slightly moveable.

Synovial Joints

A structural classification of joints where bones connect with dense connective tissues and a fluid-filled joint cavity, allowing the most movement.

Gliding (Plane) Joint

A synovial joint type allowing gliding movements; examples include intercarpal (wrist) and intertarsal (ankle) joints.

Hinge Joint

A synovial joint type allowing flexion and extension; examples include the elbow and interphalangeal (finger) joints.

Pivot Joint

A synovial joint type allowing rotation and supination/pronation; found where the humerus meets the radius and ulna at the elbow.

Condylar Joint

A synovial joint type that permits flexion/extension and abduction/adduction; found in the wrist.

Saddle Joint

A synovial joint type that allows opposition, flexion/extension, and abduction/adduction; found in the thumb.

Ball and Socket Joint

A synovial joint type allowing rotation, flexion/extension, and abduction/adduction; examples include the shoulder and hips.

Isotonic Contraction

A type of muscle contraction that causes a change in the length of the muscle, such as during a push-up.

Isometric Contraction

A type of muscle contraction that does not cause a change in the length of the muscle, such as when holding a plank.

Soleus

A muscle of the lower appendage that contracts during foot flexion, originating on the fibula and tibia and inserting into the calcaneus.

Insertion

The attachment point of a muscle to a movable bone.

Origin

The attachment point of a muscle to an immovable bone.

Prime Mover (Agonist)

Muscles that are most responsible for producing a specific movement.

Antagonist

Muscles that oppose or reverse a particular movement.

Synergist

Muscles that assist the prime mover by stabilizing across a joint or adding extra force.

Fixator

Synergist muscles that specifically immobilize a muscle's origin bone to increase the effectiveness of the prime mover.

Myofibrils

Organelles that make up the majority of muscle cells.

Myofilaments

Filaments (actin and myosin) that run along the entire length of each myofibril.

Sarcomeres

The contractile units of muscle tissue that make up myofibrils.

Muscle Fibers

Muscle cells specialized to contract, composed of bunched-together myofibrils.

Fascicles

Bundles of individual muscle fibers.

Epimysium

Dense connective tissue wrapping around the exterior of an entire muscle.

Perimysium

Connective tissue surrounding each individual fascicle.

Endomysium

Connective tissue sheath that surrounds each individual muscle fiber.

Resting Membrane Potential

The baseline electrical voltage across a cell membrane, typically measuring between $-50\text{ to }-90\text{ mV}$.

Action Potential (AP)

A large, rapid change in membrane potential that spreads over long distances within a cell via ion flow through ion channels.

Neuromuscular Junction (Motor End Plate)

The site where axon terminals of a motor neuron meet a muscle fiber, including the intervening synaptic cleft.

Motor Unit

A group of muscle fibers stimulated by a single motor neuron, producing a unified contraction felt throughout the entire muscle.