🫁 Respiratory System Study Guide

🫁 Respiratory System Study Guide

Everything you need to know for your exam

🌬 1. Major Functions of the Respiratory System

  • Gas exchange (O₂ in, CO₂ out) — occurs only in the alveoli

  • Regulates blood pH
    → By controlling CO₂ levels (↑ CO₂ = ↓ pH)

  • Speech production
    → Air passes through the larynx and vibrates the vocal folds

  • Filtering, warming, and humidifying air (upper respiratory tract)

  • Protection
    → Mucus, cilia, cough reflex

🏛 2. Upper vs Lower Respiratory Tract

Upper Respiratory Tract

  • Nasal cavity

  • Pharynx (nasopharynx, oropharynx, laryngopharynx)

  • Larynx

Lower Respiratory Tract

  • Trachea

  • Bronchi

  • Bronchioles (NO cartilage)

  • Alveoli (gas exchange)

🔍 3. Key Structures & Their Roles

Nasal Conchae

  • Increase surface area

  • Filter air

  • Humidify and warm inhaled air

Pharynx Regions

  • Oropharynx + laryngopharynx → shared for food + air

  • Lined with stratified squamous epithelium (protection)

Larynx

Functions:

  • Voice production

  • Air passage

  • Prevents food entering trachea
    Not for gas exchange

Important structures:

  • Epiglottis — blocks food from entering the larynx

  • Thyroid cartilage — forms "Adam’s apple"

  • Cricoid cartilage — only complete ring of cartilage

  • Intrinsic muscles — adjust tension of vocal cords

🫁 4. Trachea & Bronchi

Trachea

  • Lined with pseudostratified ciliated columnar epithelium

  • Supported by C-shaped hyaline cartilage rings (not full rings)

  • Ends at the carina → extremely sensitive cough reflex point

Bronchi

  • Right main bronchus is wider, shorter, more vertical
    → More likely for aspiration

Bronchioles

  • Absolutely NO cartilage

  • Smooth muscle regulates airway diameter

🫧 5. Alveoli & Gas Exchange

Type I alveolar cells

  • Thin

  • Form respiratory membrane

  • Site of gas exchange

Type II alveolar cells

  • Produce surfactant → reduces surface tension → prevents collapse

Hilum

  • Region where bronchi, blood vessels, and nerves enter/leave lung

Pleural Cavity & Fluid

  • Space between visceral & parietal pleura

  • Pleural fluid → lubricates lungs, reduces friction

🫁 6. Lung Anatomy

Right lung

  • 3 lobes: superior, middle, inferior

Left lung

  • 2 lobes

  • Has cardiac notch

💨 7. Muscles of Breathing

Inspiration (breathing in)

  • Diaphragm (main muscle)

  • External intercostals (active inspiration)

Forced Exhalation

  • Internal intercostals

  • Abdominal muscles

🧪 8. Respiratory Volumes and Capacities

Tidal Volume (TV)

  • Normal quiet breathing amount

Inspiratory Reserve Volume (IRV)

  • Extra air you can inhale after TV

Expiratory Reserve Volume (ERV)

  • Extra air you can exhale after TV

Residual Volume (RV)

  • Air left in lungs after forceful exhalation

Inspiratory Capacity (IC)

  • TV + IRV

  • Max usable inhalation volume

Functional Residual Capacity (FRC)

  • ERV + RV

  • Air remaining after normal exhalation

Vital Capacity (VC)

  • TV + IRV + ERV

  • Max amount you can inhale + exhale