Applied Resp – Other Functions

Master answer

Filter

• Narrow capillary bed
• Large particles prevented from returning to systemic circulation
  • Blood clots → stroke
  • Bacteria → killed by macrophages

Immunological

• Numerous macrophages present in lung
• Secretes IgA

Reservoir

9% of blood normally contained within pulmonary vasculature

• Sympathetic stimulation or straining (increase intrathoracic pressure
  • Blood mobilised to systemic circulation
• Able to absorb blood volue
  • Increase pulmonary artery pressure
    • → Recruitment of pulmonary alveoli
      • → Increased lung blood volume

Metabolic

• α1-antitrypsin
  • Removal of proteases

Endocrine

• Renin/angiotensin/aldosterone axis
  • Lung is main source of ACE
  • Angiotensin I —ACE—> angiotensin 2

Thermoregulation

• Humidification and warming on inspiration
• Cooling and condensation on expiration
  • Prevents excessive loss of heat

Inhalational agents

• Route of administration for drugs e.g. bronchodilators

Sequestration of drugs (“taking up drugs”)

• Fentanyl has affinity for lungs
  • Contributes to large VoD

Surfactant production

• Reduces alveolar surface tension
  • Prevents alveolar collapse and overdistension
• From type 2 pneumocytes

Mnemonic: FIRM TITS

Mooney 2016

Answer by Mooney