Respiratory System Notes

Functions of the Respiratory System

• Gas Distribution: The respiratory system serves to bring air into the body, facilitate gas exchange, and expel air.
• Molecular Exchange: Exchange of oxygen (O2) and carbon dioxide (CO2) occurs between air and blood in the lungs and between blood and systemic tissues.
• Cellular respiration: Oxygen is utilized in cellular metabolism to produce ATP, generating CO2 as a byproduct.

Structures of the Respiratory System

• Overview of Components: Includes the nose, nasal passages, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.
• Divisions:
  • Upper Respiratory Tract: Nose, nasal cavity, pharynx, larynx.
  • Lower Respiratory Tract: Trachea, bronchi, bronchioles, lungs, and alveoli.
• Zones:
  • Conducting Zone: Pathways that transport air (nose to terminal bronchioles).
  • Respiratory Zone: Sites of gas exchange (respiratory bronchioles and alveoli).

Mucosa and Goblet Cells

• Respiratory Mucosa: The entire respiratory tract is lined with mucous membranes (epithelium + lamina propria) that secrete mucus by goblet cells and serous glands.
• Thinning of Epithelium: The epithelium progressively thins from the nasal cavity to the alveoli.

Functions of the Respiratory Tract

• Air Passageway: Conducts air to the lungs.
• Gas Exchange: Transfer of O2 and CO2 between air and blood.
• Olfaction: Houses receptors for smell.
• Sound Production: Vibrates vocal cords to produce sound.
• Blood pH Regulation: Participates in acid-base balance by regulating CO2 levels in blood.

The Nose and Nasal Cavity

• Functions:
  • Warming, cleansing, and humidifying incoming air.
  • Detecting odors and amplifying voice.
• Nasal Cavity Structure:
  • Divided by the nasal septum into two halves, each containing conchae which increase surface area for air processing.
  • Paranasal Sinuses: Connect to the nasal cavity, aiding in air conditioning and resonance for voice.

Pharynx Structure and Regions

• Connection: The pharynx connects the nasal cavity to the larynx, divided into three regions:
  • Nasopharynx: Houses pharyngeal tonsils.
  • Oropharynx: Contains palatine and lingual tonsils.
  • Laryngopharynx: Connects to larynx and esophagus.

Larynx Functions and Structure

• Functions: Provides air passage, sound production, and prevents food aspiration during swallowing.
• Structure: Composed of nine cartilages; epiglottic, thyroid (Adam's apple), cricoid (connects to trachea), and paired cartilages (arytenoid, corniculate, cuneiform).

Trachea and Bronchial Tree

• Trachea: Flexible tube anterior to esophagus, supported by C-shaped cartilage rings.
• Bronchial Tree: Trachea divides into left and right main bronchi, branching into lobar and segmental bronchi, leading to bronchioles.

Alveoli and Gas Exchange

• Alveoli: Microscopic air sacs where gas exchange occurs; surround by pulmonary capillaries.
• Type I Cells: Simple squamous cells facilitating gas exchange.
• Type II Cells: Secrete surfactant to reduce surface tension, preventing alveolar collapse.

Respiratory Membrane

• Composition: Formed by alveolar epithelium, fused basement membrane, and capillary endothelium, allowing O2 and CO2 to diffuse across.
• Efficiency Factors: Surface area and membrane thickness significantly affect gas exchange efficacy.

Respiratory Processes

• Pulmonary Ventilation: Moving air into/out of the lungs (inspiration/expiration).
• Gas Exchange:
  • Pulmonary Gas Exchange: Between lungs and blood.
  • Tissue Gas Exchange: Between blood and systemic tissues.
• Gas Transport: Through hemoglobin and blood plasma.

Regulation of Gas Exchange

• Partial Pressure Gradients: Gases move from high to low partial pressures, influencing how O2 and CO2 are exchanged.
• Chemical Factors: Blood pH, temperature, and levels of CO2 influence gas binding and release from hemoglobin.

Summary of Respiratory Volumes and Capacities

• Tidal Volume (TV): About 500 mL per breath.
• Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), Residual Volume (RV), and various capacities measured through spirometry indicate lung function and health.
• Minute Ventilation: Volume of air breathed per minute, critical for diagnosing respiratory issues.

Clinical Views on Respiratory Issues

• Understanding conditions like asthma, COPD, and pneumonia can aid in identifying respiratory complications.
• Homeostatic Imbalances: Conditions impacting respiratory efficiency include airway obstructions and disorders associated with the skeletal and muscular systems affecting breathing.