Key Takeaways
- The adult human skeleton has 206 bones divided into the axial skeleton (80 bones) and appendicular skeleton (126 bones)
- The five types of bones are long, short, flat, irregular, and sesamoid
- There are three types of joints: synarthroses (immovable), amphiarthroses (slightly movable), and diarthroses (freely movable)
- Synovial joints are the most common type of diarthrosis and contain synovial fluid for lubrication
- The three types of muscle tissue are skeletal (voluntary, striated), smooth (involuntary, non-striated), and cardiac (involuntary, striated)
- Skeletal muscle contraction follows the sliding filament theory: actin and myosin filaments slide past each other
- A motor unit consists of a motor neuron and all the muscle fibers it innervates
- Major muscles for massage include the trapezius, latissimus dorsi, pectoralis major, deltoid, biceps brachii, triceps brachii, quadriceps, hamstrings, and gastrocnemius
Last updated: February 2026
Skeletal & Muscular Systems
Understanding the skeletal and muscular systems is foundational for massage therapy practice. These systems work together to produce movement, provide structural support, and protect vital organs.
The Skeletal System
Overview
The adult human skeleton contains 206 bones organized into two divisions:
| Division | Bones | Components |
|---|---|---|
| Axial Skeleton | 80 | Skull (22), hyoid (1), vertebral column (26), thoracic cage (25), auditory ossicles (6) |
| Appendicular Skeleton | 126 | Upper limbs (64), lower limbs (62), pectoral girdle, pelvic girdle |
Types of Bones
| Type | Shape | Examples |
|---|---|---|
| Long bones | Longer than wide, shaft with two ends | Femur, humerus, tibia, radius, ulna |
| Short bones | Roughly cube-shaped | Carpals (wrist), tarsals (ankle) |
| Flat bones | Thin, broad, slightly curved | Sternum, ribs, scapulae, cranial bones |
| Irregular bones | Complex shapes | Vertebrae, sacrum, mandible |
| Sesamoid bones | Small, embedded in tendons | Patella (kneecap) |
The Vertebral Column
The vertebral column consists of 26 bones (in adults) organized into five regions:
| Region | Vertebrae | Curvature | Key Features |
|---|---|---|---|
| Cervical | 7 (C1-C7) | Lordotic (concave posterior) | Atlas (C1), axis (C2), most mobile region |
| Thoracic | 12 (T1-T12) | Kyphotic (convex posterior) | Articulate with ribs |
| Lumbar | 5 (L1-L5) | Lordotic | Largest vertebrae, bear most body weight |
| Sacrum | 1 (5 fused) | Kyphotic | Articulates with pelvis at SI joints |
| Coccyx | 1 (3-5 fused) | — | Tailbone |
Types of Joints
| Joint Type | Movement | Examples |
|---|---|---|
| Synarthroses | Immovable | Cranial sutures |
| Amphiarthroses | Slightly movable | Intervertebral discs, pubic symphysis |
| Diarthroses (Synovial) | Freely movable | Shoulder, hip, knee, elbow |
Synovial Joint Features
Synovial joints are the most common and most clinically relevant for massage therapy:
- Joint capsule: Encloses the joint and holds synovial fluid
- Synovial membrane: Lines the capsule and produces synovial fluid
- Synovial fluid: Lubricates the joint, reduces friction, nourishes cartilage
- Articular cartilage: Hyaline cartilage covering bone ends, absorbs shock
- Ligaments: Connect bone to bone, stabilize the joint
- Tendons: Connect muscle to bone, transmit force for movement
- Bursae: Fluid-filled sacs that reduce friction between structures
The Muscular System
Three Types of Muscle Tissue
| Type | Location | Control | Appearance | Function |
|---|---|---|---|---|
| Skeletal | Attached to bones | Voluntary | Striated (striped) | Movement, posture, heat production |
| Smooth | Organ walls, blood vessels | Involuntary | Non-striated | Peristalsis, vasoconstriction/dilation |
| Cardiac | Heart wall only | Involuntary | Striated with intercalated discs | Pumps blood throughout the body |
Skeletal Muscle Structure
Each skeletal muscle has a hierarchical structure:
- Muscle → made of bundles of fascicles
- Fascicle → made of bundles of muscle fibers (cells)
- Muscle fiber → made of myofibrils
- Myofibril → made of sarcomeres (the functional contractile unit)
- Sarcomere → contains actin (thin) and myosin (thick) filaments
The Sliding Filament Theory
Muscle contraction occurs when actin and myosin filaments slide past each other within the sarcomere:
- A nerve impulse reaches the neuromuscular junction
- Acetylcholine (ACh) is released, stimulating the muscle fiber
- Calcium ions are released from the sarcoplasmic reticulum
- Calcium binds to troponin, exposing active binding sites on actin
- Myosin heads attach to actin, forming cross-bridges
- Myosin heads pull actin toward the center of the sarcomere (power stroke)
- ATP provides energy for the myosin heads to detach and reattach
- The sarcomere shortens, producing contraction
Major Muscles for Massage Therapy
| Muscle | Location | Primary Action |
|---|---|---|
| Trapezius | Upper back/neck | Elevates, retracts, depresses scapula; extends neck |
| Latissimus dorsi | Lower/mid back | Extends, adducts, medially rotates humerus |
| Erector spinae | Along the spine | Extends and laterally flexes the vertebral column |
| Pectoralis major | Chest | Flexes, adducts, medially rotates humerus |
| Deltoid | Shoulder | Abducts, flexes, extends humerus |
| Biceps brachii | Anterior upper arm | Flexes elbow, supinates forearm |
| Triceps brachii | Posterior upper arm | Extends elbow |
| Quadriceps | Anterior thigh | Extends knee, flexes hip (rectus femoris) |
| Hamstrings | Posterior thigh | Flexes knee, extends hip |
| Gastrocnemius | Posterior lower leg | Plantarflexes ankle, assists knee flexion |
| Gluteus maximus | Buttock | Extends and laterally rotates hip |
| Iliopsoas | Deep hip | Primary hip flexor |
| Piriformis | Deep buttock | Laterally rotates hip |
| SCM (Sternocleidomastoid) | Anterior/lateral neck | Flexes neck, rotates head to opposite side |
| Scalenes | Lateral neck | Laterally flexes neck, assists inhalation |
Connective Tissue Layers
Understanding connective tissue is essential for massage therapists who work with fascia, tendons, and ligaments:
Muscle Connective Tissue
- Epimysium — surrounds the entire muscle
- Perimysium — surrounds individual fascicles (bundles of fibers)
- Endomysium — surrounds individual muscle fibers
- All three layers merge to form the tendon at each end of the muscle
Fascia
Fascia is a continuous web of connective tissue that surrounds and connects all structures in the body:
| Type | Location | Function |
|---|---|---|
| Superficial fascia | Just under the skin | Stores fat, provides insulation, allows skin to move over deeper structures |
| Deep fascia | Around muscles, bones, nerves, blood vessels | Provides structure, transmits force, separates compartments |
| Visceral (subserous) fascia | Around organs | Suspends and supports organs |
Fascia and Massage
- Fascia contains mechanoreceptors that respond to pressure and stretch
- Prolonged, sustained pressure causes the thixotropic effect — fascia transitions from a gel state to a more fluid (sol) state
- Myofascial release techniques target fascial restrictions
- Fascial adhesions can restrict movement and cause pain
Other Body Systems Overview
Respiratory System
- Primary function: Gas exchange (O2 in, CO2 out)
- Key structures: Nasal cavity, pharynx, larynx, trachea, bronchi, lungs, alveoli
- Diaphragm: Primary muscle of respiration — massage can help relax a tight diaphragm
- Massage effects: Promotes deeper, slower breathing through relaxation; tapotement on the rib cage can loosen respiratory secretions
Digestive System
- Primary function: Breaks down food, absorbs nutrients, eliminates waste
- Key structures: Mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas
- Massage effects: Abdominal massage (clockwise direction following the colon) can promote peristalsis and relieve constipation
- Parasympathetic activation from massage enhances digestive function
Urinary System
- Primary function: Filters blood, removes waste, maintains fluid and electrolyte balance
- Key structures: Kidneys, ureters, bladder, urethra
- Massage effects: May increase urinary output due to improved circulation; clients should stay hydrated after massage
- Endangerment site: Kidneys are located at T12-L3 posteriorly — use caution with deep pressure in this area
Endocrine System
- Primary function: Produces hormones that regulate metabolism, growth, reproduction, and stress response
- Key glands: Pituitary, thyroid, adrenal, pancreas, ovaries/testes
- Massage effects: Reduces cortisol (stress hormone), increases serotonin and dopamine, may improve insulin sensitivity
- Clinical relevance: Clients with thyroid disorders may have altered metabolism; clients with diabetes require careful attention to blood sugar levels
Loading diagram...
Test Your Knowledge
How many bones are in the adult human skeleton?
A
B
C
D
Test Your Knowledge
Which type of joint is freely movable and contains synovial fluid?
A
B
C
D
Test Your Knowledge
Which type of muscle tissue is voluntary and striated?
A
B
C
D
Test Your Knowledge
What structure connects muscle to bone?
A
B
C
D
Test Your KnowledgeMulti-Select
Which of the following are components of a synovial joint? (Select all that apply)
Select all that apply
Joint capsule
Synovial fluid
Articular (hyaline) cartilage
Intervertebral disc
Ligaments
Suture lines
Test Your KnowledgeMatching
Match each muscle to its primary action.
Match each item on the left with the correct item on the right
1
Biceps brachii
2
Quadriceps group
3
Hamstrings group
4
Gastrocnemius
5
Deltoid
Test Your Knowledge
How many vertebrae are in the cervical region of the spine?
A
B
C
D
Test Your KnowledgeFill in the Blank
The functional contractile unit of a muscle fiber is called a ___.
Type your answer below
Test Your Knowledge
Which type of bone is the patella (kneecap) classified as?
A
B
C
D
Test Your Knowledge
Which connective tissue layer surrounds individual muscle fascicles?
A
B
C
D
Test Your KnowledgeOrdering
Arrange the skeletal muscle structure from largest to smallest.
Arrange the items in the correct order
1
Myofibrils
2
Whole muscle
3
Sarcomeres
4
Fascicles
5
Muscle fibers (cells)