Study Guide: The Respiratory System – Anatomy & Physiology

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Gas Exchange: The primary function is to facilitate the exchange of oxygen and carbon dioxide between the atmosphere and the bloodstream.
Regulation of Blood pH: The respiratory system helps regulate the pH of body fluids by controlling the levels of carbon dioxide in the blood.
Protection: The system filters, warms, and humidifies incoming air, protecting delicate alveolar surfaces from environmental variations and pathogens.
Vocalization: The movement of air through the larynx enables speech and other vocalizations.

Pulmonary Circuit: Oxygen enters the blood and carbon dioxide is removed in the lungs.
Systemic Circuit: Oxygen is delivered to tissues and carbon dioxide is collected from tissues for removal.
Key Process: Gas exchange occurs by diffusion across thin respiratory membranes.

Nose/Nasal Cavity: Filters, warms, and moistens air; detects odors.
Pharynx: Passageway for air and food; aids in vocalization.
Larynx: Contains vocal cords; protects lower airways.
Trachea: Conducts air to bronchi; lined with cilia to trap debris.
Bronchi and Bronchioles: Distribute air to each lung; further branch into smaller airways.
Lungs: Main organs of gas exchange; contain alveoli where exchange occurs.

Conducting Zone: Includes all structures that provide a passageway for air to move in and out of the lungs (nose to terminal bronchioles). No gas exchange occurs here.
Respiratory Zone: Includes respiratory bronchioles, alveolar ducts, and alveoli. This is where gas exchange occurs.

Structure: Composed of alveolar epithelium, capillary endothelium, and their fused basement membranes.
Function: Provides a thin barrier for efficient gas exchange between air in the alveoli and blood in the capillaries.

Atmospheric Pressure (Patm): Pressure exerted by air outside the body.
Intrapulmonary (Alveolar) Pressure (Palv): Pressure within the alveoli.
Intrapleural Pressure (Pip): Pressure within the pleural cavity; always slightly negative relative to Palv to keep lungs inflated.
Relationship: Air flows from areas of higher to lower pressure; changes in thoracic volume alter these pressures to drive ventilation.

Elastic Recoil: Lungs tend to recoil inward, while the chest wall tends to expand outward, creating a negative pressure in the intrapleural space.
Surface Tension: Fluid in the alveoli creates surface tension, further promoting lung collapse and contributing to negative intrapleural pressure.

Boyle’s Law: (Pressure and volume are inversely related in a closed system at constant temperature.)
Inspiration: Diaphragm and external intercostal muscles contract, increasing thoracic volume and decreasing alveolar pressure, causing air to flow in.
Expiration: Muscles relax, thoracic volume decreases, alveolar pressure increases, and air flows out.

Airway Resistance: Increased resistance (e.g., in asthma) makes breathing more difficult.
Lung Compliance: The ease with which lungs can expand; decreased in conditions like fibrosis.
Alveolar Surface Tension: Surfactant reduces surface tension, preventing alveolar collapse.

Tidal Volume (TV): Volume of air inhaled or exhaled in a normal breath.
Inspiratory Reserve Volume (IRV): Additional air that can be inhaled after a normal inhalation.
Expiratory Reserve Volume (ERV): Additional air that can be exhaled after a normal exhalation.
Residual Volume (RV): Air remaining in lungs after maximal exhalation.
Vital Capacity (VC):
Total Lung Capacity (TLC):

Atmospheric Air: ~78% nitrogen, 21% oxygen, 0.04% carbon dioxide, variable water vapor.
Alveolar Air: Lower oxygen, higher carbon dioxide and water vapor due to gas exchange and humidification.

Dalton’s Law: Each gas in a mixture exerts its own pressure, called partial pressure.
Henry’s Law: The amount of gas that dissolves in a liquid is proportional to its partial pressure and solubility.
Application: Oxygen and carbon dioxide diffuse across the respiratory membrane according to their partial pressure gradients.

Surface Area: Greater alveolar surface area increases gas exchange.
Membrane Thickness: Thicker membranes (e.g., in pulmonary edema) slow diffusion.
Partial Pressure Gradients: Larger gradients increase diffusion rates.
Ventilation-Perfusion Coupling: Matching of air flow and blood flow in the lungs optimizes gas exchange.

Oxygen: Mostly transported bound to hemoglobin in red blood cells; a small amount is dissolved in plasma.
Carbon Dioxide: Transported as bicarbonate ions (majority), bound to hemoglobin, and dissolved in plasma.
Factors Affecting Oxygen Release: Temperature, pH (Bohr effect), and levels of 2,3-BPG influence hemoglobin’s affinity for oxygen.

Medullary Respiratory Centers: The medulla oblongata contains the dorsal and ventral respiratory groups that set the basic rhythm of breathing.
Pontine Respiratory Centers: The pons modifies the rhythm and smooths transitions between inspiration and expiration.

Central Chemoreceptors: Located in the medulla, they respond to changes in CO2 and pH in cerebrospinal fluid.
Peripheral Chemoreceptors: Located in carotid and aortic bodies, they respond to changes in blood O2, CO2, and pH.
CO2 as Primary Driver: Increased CO2 (hypercapnia) stimulates increased ventilation; decreased CO2 (hypocapnia) suppresses ventilation.

Homeostasis in the Respiratory System: The respiratory system maintains homeostasis by regulating gas exchange, pH, and responding to metabolic demands.
Major Anatomical Features: Includes the upper and lower respiratory tracts, alveoli, and associated muscles and nerves.