Overview
The musculoskeletal system provides structural support, protects internal organs, maintains posture, and enables movement.
It consists of bones, skeletal muscles, joints, tendons, ligaments, cartilage, and other connective tissues.
The system also supports mineral storage, blood cell production, and heat generation.
Major Structures
Skeletal System
- Bones: Provide support, protect organs, store minerals such as calcium and phosphorus, and contain bone marrow.
- Axial Skeleton: Skull, vertebral column, ribs, and sternum. Supports the body’s central axis and protects vital organs.
- Appendicular Skeleton: Arms, legs, shoulders, and pelvic girdle. Supports movement and locomotion.
- Joints: Connections between bones that provide stability and, depending on the joint, permit movement.
- Tendons: Connect muscles to bones, transmitting force to produce movement.
- Ligaments: Connect bones to other bones, helping stabilize joints.
- Cartilage: Flexible connective tissue that cushions joints and supports structures such as the rib cage.
- Bone Marrow: Tissue within bones. Red marrow produces blood cells; yellow marrow primarily stores fat.
Muscular System
- Skeletal Muscle: Attached to bones through tendons. Produces voluntary movement and maintains posture.
- Smooth Muscle: Involuntary muscle found in structures such as blood vessels, the digestive tract, and bladder.
- Cardiac Muscle: Specialized involuntary muscle that contracts to pump blood through the heart.
Vertebral Column
The spine supports the body, protects the spinal cord, and allows movement.
| Region | Structure |
|---|---|
| Cervical | 7 vertebrae in the neck |
| Thoracic | 12 vertebrae in the upper and middle back |
| Lumbar | 5 vertebrae in the lower back |
| Sacrum | 5 fused vertebrae connecting the spine to the pelvis |
| Coccyx | Tailbone, typically formed from 3–5 fused vertebrae |
Intervertebral Discs: Fibrocartilaginous structures between most adjacent movable vertebrae that absorb shock and permit movement.
Other Important Structures
- Temporomandibular Joint (TMJ): Connects the mandible (lower jaw) to the temporal bone of the skull, allowing chewing and speaking.
- Pelvis: Connects the spine to the lower limbs, supports body weight, and protects pelvic organs.
- Hip Joint: Ball-and-socket joint connecting the femur to the pelvis.
Key Processes
- Muscle Contraction: Produces movement, maintains posture, and stabilizes joints.
- Joint Movement: Includes flexion, extension, abduction, adduction, and rotation.
- Weight Bearing: Bones, muscles, and joints support body weight during standing, walking, and transfers.
- Bone Remodeling: Continuous breakdown and replacement of bone tissue.
- Thermoregulation: Muscle activity generates heat; shivering produces heat through repeated involuntary contractions.
- Blood Cell Production (Hematopoiesis): Red bone marrow produces red blood cells, white blood cells, and platelets.
- Mineral Storage: Bones store calcium and phosphorus and help regulate their availability.
- Support of Elimination: Skeletal and smooth muscles help control urination and defecation.
Effects of Aging
- Reduced Bone Density: Bone mass may decline, increasing vulnerability to fractures.
- Reduced Muscle Mass (Sarcopenia): Loss of muscle mass and strength can impair mobility and balance.
- Reduced Flexibility: Changes in connective tissues and joints may limit range of motion.
- Slower Muscle Responses: Changes in muscle and nervous-system function can affect coordination and reaction time.
- Reduced Physical Endurance: Fatigue may occur more easily during prolonged activity.
Clinical Implications
- Increased risk of falls and fractures.
- Greater difficulty with transfers, walking, and ADLs.
- Increased vulnerability to deconditioning during prolonged bed rest.
- Greater importance of appropriate mobility, exercise, and restorative care.
- Encourage independence while following individualized mobility restrictions.
Important: Osteoporosis, severe weakness, and inability to walk are not inevitable consequences of aging. New functional decline should be reported.
Common Diseases & Disorders
| Condition | Description | Common Causes / Risk Factors | CNA Considerations |
|---|---|---|---|
| Osteoarthritis | Degenerative joint disease involving cartilage and other joint tissues, causing pain and stiffness | Aging, previous joint injuries, obesity, repetitive joint stress, genetics | Observe pain, stiffness, and mobility limitations |
| Rheumatoid Arthritis | Autoimmune inflammatory disease causing joint pain, swelling, and stiffness | Immune system attacks joint tissues; genetic susceptibility and smoking increase risk | Follow joint-protection precautions and report worsening symptoms |
| Osteoporosis | Reduced bone density and strength, increasing fracture risk; may cause kyphosis following vertebral fractures | Aging, hormonal changes after menopause, inactivity, low calcium or vitamin D, certain medications | Follow fall-prevention precautions and safe transfer techniques; encourage prescribed weight-bearing activity |
| Fractures | Partial or complete breaks in a bone | Falls, trauma, osteoporosis, repetitive stress | Avoid unnecessary movement and immediately report suspected fractures |
| Sprains | Stretching or tearing of ligaments | Twisting a joint, falls, sudden movements, sports injuries | Observe swelling, bruising, pain, and impaired movement |
| Strains | Stretching or tearing of muscles or tendons | Overexertion, improper lifting, repetitive movements, sudden stretching | Report pain, weakness, or difficulty moving |
| Contractures | Persistent shortening or tightening of muscles, tendons, or other tissues that restrict joint movement | Prolonged immobility, neurological conditions, muscle imbalance, scar tissue | Follow prescribed positioning and range-of-motion plans |
| Muscle Atrophy | Reduction in muscle size and mass | Immobility, disuse, aging, malnutrition, neurological disease | Encourage permitted activity and report functional decline |
Important: CNAs observe and report musculoskeletal problems rather than independently diagnosing injuries or determining treatment.
Important Distinctions
- Osteoarthritis vs. Rheumatoid Arthritis: Osteoarthritis involves degenerative changes affecting cartilage and other joint tissues. Rheumatoid arthritis is an autoimmune inflammatory disease that can affect multiple joints and other organs.
- Sprain vs. Strain: A sprain involves ligaments; a strain involves muscles or tendons.
- Osteopenia vs. Osteoporosis: Osteopenia means bone mineral density is lower than normal; osteoporosis involves more substantial skeletal fragility and increased fracture risk.
- Muscle Atrophy vs. Contracture: Atrophy is loss of muscle mass. A contracture is persistent shortening or tightening of tissues that restricts joint movement.
When to Report
- New or worsening joint or muscle pain.
- Sudden difficulty walking, standing, or transferring.
- Swelling, bruising, or visible deformity after an injury.
- Reduced range of motion or increasing stiffness.
- New weakness or unexpected functional decline.
- Signs of injury following a fall.
Suspected fractures, sudden severe pain after injury, or new one-sided weakness require urgent evaluation. Follow emergency-response procedures when indicated.
Study Notes
Clinical Connections
- Limited Mobility: Reduced mobility can lead to weakness, contractures, and other complications.
- Patient Positions: Proper alignment supports comfort, joint positioning, and pressure prevention.
- Range-of-Motion Exercises: Prescribed exercises help maintain joint mobility.
- Assisting with Ambulation: Safe walking assistance promotes mobility and independence.
- Safe Patient Transfers: Proper transfer techniques reduce injury risk.
- Body Mechanics & Injury Prevention: Safe movement protects residents and caregivers.
- Restorative & Rehabilitative Care: Individualized activities help maintain or restore function.
- Fall Risk: Weakness, balance changes, and reduced mobility can increase fall risk.
Questions
- What distinguishes the axial and appendicular skeletons?
- What are the three types of muscle tissue?
- How do tendons and ligaments differ?
- What are the five regions of the vertebral column?
- What is the role of bone marrow?
- How do muscles help regulate body temperature?
- How does aging affect bone density, muscle strength, and mobility?
- What distinguishes osteoarthritis from rheumatoid arthritis?
- What is the difference between a sprain and a strain?
- Why does prolonged immobility increase the risk of muscle atrophy and contractures?
- How can CNAs help maintain musculoskeletal function?
Sources
- CNA Module 13 — Anatomy, Physiology & Aging
- MedlinePlus — Bones, Joints and Muscles
- National Institute on Aging — Exercise and Physical Activity
Flashcards
What are the two major divisions of the skeleton?01-foundations / anatomy-physiology / musculoskeletal
Answer
Axial and appendicular skeletons.
What structures make up the axial skeleton?01-foundations / anatomy-physiology / musculoskeletal
Answer
Skull, vertebral column, ribs, and sternum.
What structures make up the appendicular skeleton?01-foundations / anatomy-physiology / musculoskeletal
Answer
Upper and lower limbs, shoulder girdle, and pelvic girdle.
What are the three types of muscle tissue?01-foundations / anatomy-physiology / musculoskeletal
Answer
Skeletal, smooth, and cardiac.
What is the difference between tendons and ligaments?01-foundations / anatomy-physiology / musculoskeletal
Answer
Tendons connect muscle to bone; ligaments connect bone to bone.
What is the primary function of cartilage in joints?01-foundations / anatomy-physiology / musculoskeletal
Answer
Provide smooth surfaces and cushioning to reduce friction.
What are the five regions of the vertebral column?01-foundations / anatomy-physiology / musculoskeletal
Answer
Cervical, thoracic, lumbar, sacral, and coccygeal.
How many vertebrae are in the cervical, thoracic, and lumbar regions?02-mechanisms / anatomy-physiology / musculoskeletal
Answer
7 cervical, 12 thoracic, and 5 lumbar.
What is the function of red bone marrow?01-foundations / anatomy-physiology / musculoskeletal
Answer
Produces red blood cells, white blood cells, and platelets.
How do skeletal muscles help regulate body temperature?02-mechanisms / anatomy-physiology / musculoskeletal
Answer
Muscle contractions generate heat, including through shivering.
How does aging commonly affect the musculoskeletal system?02-mechanisms / anatomy-physiology / musculoskeletal
Answer
Reduced muscle mass, strength, flexibility, and bone density.
What is the difference between osteoarthritis and rheumatoid arthritis?02-mechanisms / anatomy-physiology / musculoskeletal
Answer
Osteoarthritis is a joint disease; rheumatoid arthritis is an autoimmune inflammatory disease.
What is the difference between a sprain and a strain?01-foundations / anatomy-physiology / musculoskeletal
Answer
A sprain injures ligaments; a strain injures muscles or tendons.
What is a contracture?01-foundations / anatomy-physiology / musculoskeletal
Answer
Persistent tightening of tissues that restricts joint movement.
What should a CNA do when a resident develops sudden severe pain and cannot bear weight after a fall?03-application / anatomy-physiology / musculoskeletal
Answer
Do not attempt to stand or transfer them; summon nursing help immediately.