respiratory system

• Functions of the Respiratory System

  • Supplies the body with oxygen and disposes of carbon dioxide
  • Filters inspired air
  • Produces sound
  • Clears the body of excess water and heat
  • Controls blood pH
• Processes in Respiration

  1. Ventilation: Movement of air into and out of the lungs

  2. Gas Exchange: Between blood and lungs, and between blood and body cells

  3. Gas Transport: In the bloodstream

  4. Cellular Respiration: Utilization of oxygen by body cells
• Normal Respiratory Values

  • Respiration Rate: 12-16 breaths/min
  • Arterial Blood Gas Values: pH: 7.35 – 7.45, PaO2: 80-100 mm Hg, SaO2: 95-98%, PCO2: 35-45 mm Hg, HCO3: 22-27 mEq/L
• Pulmonary Ventilation Phases

  1. Inspiration (Inhalation): Active process requiring energy, diaphragm contracts

  2. Expiration (Exhalation): Passive process relying on elastic recoil, diaphragm relaxes
• Organs of the Respiratory System

  • Upper Respiratory Tract: Nose, nasal cavity, sinuses, pharynx
  • Lower Respiratory Tract: Larynx, trachea, bronchial tree, lungs
• Nose


  • Filters air
• Sinuses


  • Reduce skull weight, affect voice resonance
• Pharynx


  • Passageway for air and food, aids in speech
• Larynx


  • Houses vocal cords, prevents particles from entering trachea
• Trachea


  • Splits into bronchi, lined with ciliated mucous membrane
• Bronchial Tree


  • Leads from trachea to alveoli, main site of gas exchange
• Breathing Mechanism

  1. Inspiration: Involves diaphragm and external intercostal muscles; surfactant prevents alveoli collapse

  2. Expiration: Relies on elastic recoil of lung tissues; forced expiration involves abdominal muscles
• Respiratory Air Volumes and Capacities

  • Tidal Volume (TV): Air per breath (500 ml)
  • Inspiratory Reserve Volume (IRV): Additional air after normal inhale
  • Expiratory Reserve Volume (ERV): Additional air after normal exhale
  • Residual Volume (RV): Air remaining after maximal exhale
  • Vital Capacity (VC): TV + IRV + ERV
  • Total Lung Capacity (TLC): VC + RV
• Respiratory Center


  • Brainstem controls breathing rhythm and depth
• Factors Affecting Breathing


  • Chemicals
  • Lung tissue stretch
  • Emotional state
• Oxygen


  Carried mostly by hemoglobin
• Carbon Dioxide


  Transported as dissolved CO2, carbamino compounds, and bicarbonate ions
• Respiratory Disorders

  • Asthma: Chronic inflammation of airways
  • Emphysema: Damage to alveoli causing shortness of breath
  • Pneumonia: Inflammation of alveoli
  • Lung Abscess: Cavities with necrotic debris
  • Lung Collapse: Air escapes from the lung and fills the space outside the lung