Anatomy & Physiology: Skeletal System and Muscle Unit

Comprehensive practice flashcards covering bone cell types, joint movements, muscle structure, and contraction mechanisms for A&P exams.

Osteoblast

A cell that builds bone.

Osteocyte

A mature bone cell.

Osteoclast

A cell that breaks down bone.

Lacunae

Spaces containing osteocytes within compact bone structures.

Central canals

Structures that contain blood vessels and nerves.

Horizontal canals

Canals that connect central canals.

Canaliculi

Tiny channels connecting osteocytes.

Organic Bone Composition

Consists of collagen which provide flexibility.

Inorganic Bone Composition

Consists of calcium phosphate which provide hardness.

Vitamin D

Helps the body absorb calcium.

Vitamin C

Necessary for collagen formation.

Parathyroid hormone

Hormone that raises blood calcium levels.

Growth hormone

Hormone that stimulates bone growth.

Compact bone

A dense, strong, outer layer of bone that contains osteons.

Spongy bone

A porous, lightweight interior layer of bone that contains trabeculae.

Intramembranous ossification

Process where bone forms directly from connective tissue.

Endochondral ossification

Process where bone replaces a cartilage model.

Growth plates

Also known as epiphyseal plates, these allow bones to grow in length.

Synarthroses

Immovable joints.

Amphiarthrosis

Slightly movable joints.

Synovial joints

Freely movable joints.

Ball-and-socket joint

A type of synovial joint, such as the shoulder.

Hinge joint

A type of synovial joint, such as the elbow.

Pivot joint

A type of synovial joint, such as the atlas-axis.

Saddle joint

A type of synovial joint, such as the thumb.

Condyloid joint

A type of synovial joint, such as the wrist.

Plane joint

A type of synovial joint, such as the carpals.

Flexion

Movement that decreases the angle of a joint.

Extension

Movement that increases the angle of a joint.

Abduction

Movement away from the midline.

Adduction

Movement toward the midline.

Rotation

A turning movement.

Sarcolemma

The muscle cell membrane.

Sarcoplasm

The muscle cytoplasm.

Sarcoplasmic reticulum

A structure that stores calcium in muscle cells.

Actin

The thin filament in the sliding filament theory.

Myosin

The thick filament in the sliding filament theory.

Sliding Filament Theory

Process where calcium exposes binding sites and $ATP$ powers contraction as actin slides past myosin to shorten sarcomeres.

NACACA

Mnemonic for muscle contraction steps: Nerve impulse, Acetylcholine, Calcium, Actin, Cross-bridges, $ATP$.

Muscle fatigue

Condition caused by $ATP$ depletion and lactic acid buildup.

Isometric contraction

Tension generated without movement.

Isotonic contraction

Contraction where movement occurs.

Twitch

A single muscle contraction.

Summation

The combining of muscle twitches.

Incomplete tetanus

A state of partial muscle relaxation.

Complete tetanus

A sustained muscle contraction.

Aerobic respiration

Energy source used during mild exercise.

Anaerobic glycolysis

Energy source used during strenuous exercise.

Recovery oxygen uptake

Process that restores $ATP$ and removes lactic acid.

Prime mover

The main muscle responsible for a movement.

Antagonist

A muscle that opposes a movement.

Synergist

A muscle that assists a movement.

Origin

The fixed attachment of a muscle.

Insertion

The movable attachment of a muscle.