Overview
This lecture covers the structure, function, and regulation of the respiratory system, focusing on key anatomy, gas exchange, and breathing mechanisms for the ATI TEAS 7 exam.
Anatomy of the Respiratory System
- Air enters through the nasal cavity, where it is warmed, humidified, and filtered by mucus and hairs.
- The pharynx acts as a crossroad for air (toward larynx) and food (toward esophagus).
- The larynx (voice box) leads air to the trachea, while the epiglottis prevents food from entering the trachea.
- The trachea is supported by cartilage rings and splits into two primary bronchi, each leading to a lung.
- Right lung has three lobes; left lung has two lobes and a cardiac notch to accommodate the heart.
- Bronchi branch into secondary, tertiary bronchi, then into bronchioles, ending in alveolar ducts and alveolar sacs.
- Alveoli are grape-like structures where gas exchange occurs.
Respiratory Zones and Gas Exchange
- The conducting zone includes trachea, bronchi, and terminal bronchioles; it moves, warms, and filters air but does not exchange gases ("anatomical dead space").
- The respiratory zone (respiratory bronchioles, alveolar ducts, alveoli) is where gas exchange takes place.
- Alveoli provide a large surface area and rich blood supply for efficient oxygen and carbon dioxide exchange.
- Red blood cells in capillaries pick up oxygen and remove carbon dioxide for bodily distribution.
Interaction with Other Body Systems
- The skeletal system (ribs) protects the lungs.
- Muscular system (intercostal muscles, diaphragm, abdominal muscles) drives breathing by altering thoracic cavity volume.
- Nervous system controls breathing, mainly involuntarily, based on blood pH levels.
Regulation of Breathing and Blood pH
- The pH scale measures hydrogen ion concentration; low pH = acidic (high hydrogen), high pH = basic (low hydrogen).
- Increased carbon dioxide raises blood hydrogen ions, making it more acidic.
- Sensors detect pH changes and signal the brain to adjust breathing rate and depth to maintain blood pH around 7.4 (homeostasis).
- Exercise increases breathing rate and depth to meet metabolic demands.
Mechanics of Breathing
- Inspiration (inhalation) is active: diaphragm contracts and flattens, external intercostal muscles elevate the rib cage, increasing thoracic cavity volume and drawing air in.
- Expiration (exhalation) is usually passive: diaphragm and intercostal muscles relax, reducing thoracic volume and forcing air out.
- Forced expiration (cough, exercise) is active, involving additional muscle contraction.
Ventilation, Perfusion, and Breathing Imbalances
- Ventilation: movement of air into and out of the lungs.
- Perfusion: blood flow to alveolar capillaries for gas exchange.
- Optimal gas exchange requires balanced ventilation and perfusion.
- Hypoventilation: inadequate breathing increases CO₂ (hypercapnia) and decreases O₂ (hypoxia).
- Hyperventilation: excessive breathing decreases CO₂ (hypocapnia), increases O₂ (hyperoxia), and can cause respiratory alkalosis (high blood pH).
Key Terms & Definitions
- Alveoli — tiny sacs in the lungs for gas exchange.
- Bronchi/Bronchioles — airways that branch from the trachea into the lungs.
- Conducting Zone — airways that move air but do not exchange gases.
- Respiratory Zone — regions of the lungs where gas exchange occurs.
- Diaphragm — dome-shaped muscle below the lungs aiding in breathing.
- pH Scale — measures acidity/basicity via hydrogen ion concentration.
- Perfusion — blood flow through lung capillaries.
- Ventilation — movement of air in/out of lungs.
- Hypoventilation — reduced breathing; increased CO₂, decreased O₂.
- Hyperventilation — excessive breathing; decreased CO₂, increased O₂.
Action Items / Next Steps
- Review respiratory anatomy diagrams and memorize the flow of air through the system.
- Study key terms and ensure you understand their definitions.
- Practice explaining the difference between ventilation and perfusion.
- Prepare for questions on how blood pH affects breathing regulation.