Anatomy & Physiology
Essential anatomical and physiological foundations for physical therapy practice, covering the musculoskeletal, nervous, cardiovascular, and respiratory systems.
Table of Contents
1. Musculoskeletal System
Bone Structure & Classification
Bone Types
- Long bones: Femur, humerus, tibia
- Short bones: Carpals, tarsals
- Flat bones: Skull, scapula, sternum
- Irregular bones: Vertebrae, pelvis
- Sesamoid bones: Patella
Bone Tissue
- Cortical (Compact): Dense outer layer, 80% of skeleton
- Cancellous (Spongy): Inner trabecular network
- Periosteum: Outer membrane, blood vessels
- Endosteum: Inner membrane
Joint Classification
| Classification | Structure | Movement | Examples |
|---|---|---|---|
| Fibrous | Connective tissue | Minimal/None | Skull sutures, syndesmosis |
| Cartilaginous | Cartilage connection | Limited | Symphysis pubis, IVD |
| Synovial | Joint capsule, synovial fluid | Freely movable | Knee, shoulder, hip |
Synovial Joint Types
Ball & Socket
Multi-axial; hip, shoulder
Hinge
Uniaxial; elbow, knee, ankle
Pivot
Rotation; atlantoaxial, radioulnar
Condyloid
Biaxial; MCP, wrist
Saddle
Biaxial; CMC of thumb
Plane (Gliding)
Sliding; intercarpal, facet
Connective Tissues
Tendons
- • Connect muscle to bone
- • Type I collagen (parallel fibers)
- • Poor blood supply
- • Slow healing (6-8 weeks)
Ligaments
- • Connect bone to bone
- • Type I collagen (some elastin)
- • Provide joint stability
- • Grading: I (stretch), II (partial), III (complete)
Cartilage
- Hyaline: Articular surfaces, trachea
- Fibrocartilage: Meniscus, IVD, labrum
- Elastic: Ear, epiglottis
- • Avascular - poor healing
Fascia
- Superficial: Under skin
- Deep: Surrounds muscles, organs
- • Continuous tissue network
- • Myofascial release techniques
2. Muscle Physiology
Muscle Types
Skeletal Muscle
- • Voluntary control
- • Striated appearance
- • Attached to bones
- • Multi-nucleated
- • Fast fatigue (variable)
Cardiac Muscle
- • Involuntary control
- • Striated appearance
- • Heart only
- • Intercalated discs
- • Fatigue resistant
Smooth Muscle
- • Involuntary control
- • Non-striated
- • Visceral organs
- • Single nucleus
- • Slow contraction
Muscle Fiber Types
| Characteristic | Type I (Slow Twitch) | Type IIa (Fast Oxidative) | Type IIx (Fast Glycolytic) |
|---|---|---|---|
| Color | Red (high myoglobin) | Red-pink | White (low myoglobin) |
| Metabolism | Aerobic (oxidative) | Both | Anaerobic (glycolytic) |
| Fatigue | Resistant | Intermediate | Fatigues quickly |
| Force | Low | Intermediate | High |
| Function | Posture, endurance | Walking, moderate activity | Sprinting, power |
Sliding Filament Theory
Muscle contraction occurs when actin and myosin filaments slide past each other, shortening the sarcomere.
- 1. Nerve impulse → Action potential reaches motor end plate
- 2. Calcium release → Ca²⁺ released from sarcoplasmic reticulum
- 3. Troponin-tropomyosin → Ca²⁺ binds troponin, exposing binding sites
- 4. Cross-bridge cycling → Myosin heads attach to actin, pull, release
- 5. Relaxation → Ca²⁺ pumped back, tropomyosin covers binding sites
Length-Tension Relationship
- Optimal length: Maximum overlap of actin-myosin = maximum force
- Too short: Overlapping filaments interfere
- Too long: Reduced cross-bridge formation
- Active insufficiency: Muscle too short to generate force
- Passive insufficiency: Antagonist too short, limits movement
3. Nervous System
Central Nervous System (CNS)
Brain Regions
- Cerebral cortex: Higher functions, motor planning
- Basal ganglia: Movement initiation, smooth execution
- Cerebellum: Coordination, balance, motor learning
- Brainstem: Vital functions, cranial nerves
Spinal Cord
- Cervical: C1-C8 (8 segments, 7 vertebrae)
- Thoracic: T1-T12
- Lumbar: L1-L5
- Sacral: S1-S5
- Coccygeal: Co1
Motor Pathways
Upper Motor Neurons (UMN)
From cortex to spinal cord
UMN Lesion Signs:
- • Spasticity (velocity-dependent)
- • Hyperreflexia
- • Positive Babinski sign
- • Clonus
- • Synergy patterns
Lower Motor Neurons (LMN)
From spinal cord to muscle
LMN Lesion Signs:
- • Flaccidity
- • Areflexia/Hyporeflexia
- • Muscle atrophy
- • Fasciculations
- • Fibrillations (EMG)
Motor Unit & Recruitment
Motor unit: Alpha motor neuron + all muscle fibers it innervates
- Size Principle (Henneman): Smaller motor units recruited first, then larger
- All-or-none law: All fibers in a motor unit contract together
- Rate coding: Increased firing rate = increased force
- Recruitment: More motor units = more force
Reflexes
Stretch Reflex (Myotatic)
- • Monosynaptic
- • Muscle spindle detects stretch
- • Agonist contracts
- • Example: Knee jerk (L3-L4)
Inverse Stretch Reflex
- • Golgi tendon organ (GTO)
- • Detects tension
- • Causes muscle relaxation
- • Protective mechanism
4. Dermatomes & Myotomes
Key Dermatomes (Sensory)
| Level | Landmark | Clinical Testing |
|---|---|---|
| C4 | Top of shoulder | Clavicle region |
| C5 | Lateral arm (deltoid) | Shoulder abduction |
| C6 | Thumb, lateral forearm | Wrist extension |
| C7 | Middle finger | Elbow extension |
| C8 | Little finger, medial forearm | Finger flexion |
| T4 | Nipple line | Intercostal sensation |
| T10 | Umbilicus | Abdominal sensation |
| L3 | Anterior thigh | Knee extension |
| L4 | Medial leg, big toe | Ankle dorsiflexion |
| L5 | Lateral leg, dorsum foot | Big toe extension |
| S1 | Lateral foot, little toe | Ankle plantarflexion |
Key Myotomes (Motor)
Upper Extremity
- C5: Shoulder abduction, elbow flexion
- C6: Wrist extension, biceps
- C7: Elbow extension, wrist flexion
- C8: Finger flexion, grip
- T1: Finger abduction (intrinsics)
Lower Extremity
- L2: Hip flexion
- L3: Knee extension
- L4: Ankle dorsiflexion
- L5: Great toe extension
- S1: Ankle plantarflexion, hip extension
- S2: Knee flexion
Deep Tendon Reflexes
Biceps
C5-C6
Brachioradialis
C5-C6
Triceps
C7-C8
Patellar
L3-L4
Achilles
S1-S2
Grading: 0 (absent), 1+ (diminished), 2+ (normal), 3+ (brisk), 4+ (clonus)
5. Cardiovascular System
Cardiac Physiology
- Cardiac Output (CO): CO = HR × SV (Heart Rate × Stroke Volume)
- Normal CO: ~5 L/min at rest; up to 20-25 L/min during exercise
- Blood Pressure: SBP/DBP; normal <120/<80 mmHg
- MAP: DBP + 1/3(SBP - DBP) or (SBP + 2×DBP)/3
Exercise Response
Normal Response
- • HR increases with intensity
- • SBP increases (10 mmHg per MET)
- • DBP stays same or slightly decreases
- • Rate-pressure product (HR × SBP) = myocardial oxygen demand
Abnormal Response
- • SBP drop >10 mmHg with increased workload
- • DBP increase >15 mmHg
- • Failure to increase HR appropriately
- • Signs to stop: chest pain, severe dyspnea, cyanosis
Heart Rate Training Zones
HRmax = 220 - age (estimate)
- 50-60% HRmax: Warm-up, very light intensity
- 60-70% HRmax: Fat burning zone, low intensity
- 70-80% HRmax: Aerobic zone, moderate intensity
- 80-90% HRmax: Anaerobic threshold
- 90-100% HRmax: Maximum effort
6. Respiratory System
Lung Volumes & Capacities
| Measurement | Definition | Normal Value |
|---|---|---|
| Tidal Volume (TV) | Normal breath | 500 mL |
| Inspiratory Reserve (IRV) | Extra inspiration beyond TV | 3100 mL |
| Expiratory Reserve (ERV) | Extra expiration beyond TV | 1200 mL |
| Residual Volume (RV) | Air remaining after max expiration | 1200 mL |
| Vital Capacity (VC) | TV + IRV + ERV | 4800 mL |
| Total Lung Capacity (TLC) | VC + RV | 6000 mL |
Breathing Mechanics
Primary Muscles of Inspiration
- Diaphragm: Main muscle (~75% of quiet breathing)
- External intercostals: Elevate ribs
Accessory Muscles
- SCM: Elevates sternum
- Scalenes: Elevate upper ribs
- Pectorals: When arms fixed
7. Exercise Physiology
Energy Systems
ATP-PC (Phosphagen)
- • Immediate energy
- • 0-10 seconds
- • No oxygen needed
- • Power activities
Glycolytic (Anaerobic)
- • Glucose breakdown
- • 10 sec - 2 min
- • Produces lactate
- • High-intensity
Oxidative (Aerobic)
- • Oxygen required
- • 2+ minutes
- • Sustained activity
- • Most efficient
VO2max & METs
- VO2max: Maximum oxygen consumption; gold standard for cardiorespiratory fitness
- MET (Metabolic Equivalent): 1 MET = 3.5 mL O2/kg/min (resting)
- Activities: Walking 3mph = 3.3 METs; Jogging 5mph = 8 METs
- RPE (Borg Scale): 6-20 scale; multiply by 10 ≈ HR
8. Tissue Healing
Phases of Wound Healing
Phase 1: Inflammation (0-6 days)
- • Hemostasis (clot formation)
- • Vasodilation, increased permeability
- • Cardinal signs: redness, heat, swelling, pain
- • Phagocytosis of debris
- Treatment: PRICE (Protection, Rest, Ice, Compression, Elevation)
Phase 2: Proliferation (3 days - 3 weeks)
- • Fibroblast proliferation
- • Collagen synthesis (Type III initially)
- • Angiogenesis (new blood vessels)
- • Granulation tissue formation
- Treatment: Gentle ROM, isometrics, controlled loading
Phase 3: Remodeling (3 weeks - 1 year+)
- • Type I collagen replaces Type III
- • Scar tissue maturation
- • Collagen alignment along stress lines
- • Maximum strength: 70-80% of original
- Treatment: Progressive strengthening, functional activities
Factors Affecting Healing
Promote Healing:
- • Good nutrition (protein, vitamin C)
- • Adequate blood supply
- • Appropriate loading
- • Younger age
Delay Healing:
- • Diabetes, infection
- • Poor circulation
- • NSAIDs, steroids (chronic use)
- • Smoking, malnutrition
Key Takeaways for the Board Exam
Muscle Fiber Types
- • Type I: Slow, red, oxidative, fatigue-resistant
- • Type II: Fast, white, glycolytic, fatigues quickly
UMN vs LMN
- • UMN: Spasticity, hyperreflexia, Babinski+
- • LMN: Flaccidity, areflexia, atrophy
Key Dermatomes
- • C6: Thumb
- • T4: Nipple; T10: Umbilicus
- • L4: Medial leg; S1: Lateral foot
Healing Phases
- • Inflammation: 0-6 days
- • Proliferation: 3 days - 3 weeks
- • Remodeling: 3 weeks - 1 year+