Skeletal, Articulations, & Muscular System

Support

Framework that supports the body and cradles soft organs.

Protection

Shields vital organs (e.g., skull protects brain, ribs protect heart/lungs).

Movement

Muscles attach to bones via tendons; bones act as levers.

Mineral Storage

Stores calcium and phosphate; released as needed.

Hematopoiesis

Blood cell production that occurs in red bone marrow.

Triglyceride Storage

Stored in yellow bone marrow.

Osteocalcin

Hormone that regulates bone formation and insulin.

Long Bones

Bones longer than wide (e.g., femur, humerus).

Short Bones

Cube-shaped bones (e.g., carpals, tarsals).

Flat Bones

Thin, flat, often curved bones (e.g., skull, ribs, sternum).

Irregular Bones

Bones with complex shapes (e.g., vertebrae, hip bones).

Sesamoid Bones

Bones embedded in tendons (e.g., patella).

Osteogenic Cells

Stem cells that differentiate into osteoblasts.

Osteoblasts

Bone-building cells that secrete osteoid.

Osteocytes

Mature bone cells in lacunae that maintain bone matrix.

Osteoclasts

Bone-resorbing cells that break down bone.

Osteoprogenitor Cells

Cells found in periosteum and endosteum that contribute to forming new osteoblasts.

Organic Matrix

Collagen fibers and ground substance providing flexibility to bone.

Inorganic Matrix

Calcium phosphate contributing to the hardness of bone.

Compact Bone

Dense outer layer of bone made of osteons (Haversian systems).

Spongy Bone

Honeycomb-like network of trabeculae found in epiphyses and flat bones.

Epiphysis

Ends of a long bone with a spongy bone interior.

Articular Cartilage

Hyaline cartilage covering joint surfaces.

Epiphyseal Plate

Growth plate in long bones made of hyaline cartilage.

Diaphysis

Shaft of a long bone; compact bone surrounding the medullary cavity.

Medullary Cavity

Contains yellow marrow (fat) in long bones.

Periosteum

Outer membrane of bone containing osteoblasts and osteoclasts.

Endosteum

Lines the medullary cavity and is a site for bone remodeling.

Intramembranous Ossification

Bone develops from fibrous membrane, primarily in flat bones.

Endochondral Ossification

Bone replaces hyaline cartilage, typical in most bones.

Longitudinal Growth

Growth in length occurring at the epiphyseal plate.

Appositional Growth

Growth in width by adding bone to the periosteum.

Bone Remodeling

Process of bone resorption (osteoclasts) and bone deposition (osteoblasts).

Osteoporosis

Condition where bone resorption exceeds bone formation, leading to brittle bones.

Simple Fracture

A fracture that does not break the skin.

Compound Fracture

A fracture that breaks the skin.

Comminuted Fracture

A fracture where the bone shatters into several pieces.

Compression Fracture

A fracture caused by bone being crushed.

Spiral Fracture

A fracture resulting from twisting forces.

Greenstick Fracture

A partial fracture often seen in children.

Hematoma Formation

The initial blood clot formation at the fracture site.

Fibrocartilaginous Callus

Collagen and cartilage forming to stabilize a fracture.

Bony Callus

Spongy bone that replaces the fibrocartilaginous callus during healing.

Bone Remodeling Phase

The final phase where compact bone replaces spongy bone, restoring shape.

Articular Capsule

The fibrous outer and synovial inner layer surrounding a joint.

Synovial Fluid

The lubricating fluid found in the joint cavity.

Flexion

Movement that decreases the angle between body parts.

Extension

Movement that increases the angle between body parts.

Abduction

Movement away from the body's midline.

Adduction

Movement toward the body's midline.

Circumduction

Circular movement of a limb or body part.

Supination

Palm facing up or forward.

Pronation

Palm facing down or backward.

Elevation

Movement that raises a body part.

Depression

Movement that lowers a body part.

Motor Unit

A motor neuron and all muscle fibers it controls.

Isometric Contraction

Muscle tension increases without shortening.

Isotonic Contraction

Muscle shortens as it contracts to move a load.

Smooth Muscle Innervation

Involuntary innervation by the autonomic nervous system.

Excitation-Contraction Coupling

Process where action potential leads to muscle contraction.

Crossbridge Cycle

The sequence of steps involving myosin and actin during contraction.

Direct Phosphorylation

Process of producing ATP from creatine phosphate and ADP.

Anaerobic Respiration

Creation of ATP from glucose without oxygen, yielding lactic acid.

Aerobic Respiration

Process of producing ATP using glucose and oxygen, yielding carbon dioxide and water.

Fatigue

A decreased ability to contract muscles.

Atrophy

Muscle shrinkage due to disuse.

Sarcopenia

Age-related loss of muscle mass.

Hypertrophy

Increase in muscle fiber size.

Hyperplasia

Increase in fiber number, rarely occurs in humans.

Muscle Tension Factors

Include the number of motor units recruited and frequency of stimulation.

Osteoarthritis

A type of arthritis characterized by wear and tear of the cartilage.

Rheumatoid Arthritis

An autoimmune disorder affecting the synovial membrane.

Gout

A condition caused by uric acid crystal buildup in joints.