Anatomy of The Respiratory System

Major Role of Respiratory System

• Delivery of oxygen: Oxygen is transported to tissues.
• Removal of carbon dioxide: Carbon dioxide is expelled from the blood.
• Filtration, warming, and humidification: Air is processed as it enters.

Types of Respiration

• Internal Respiration: Cellular absorption of oxygen and release of CO2.
• External Respiration: Gas exchange between environment and lungs.
• Simple Diffusion: Gas exchange occurs through barriers, such as membranes.

The Thoracic Cavity

• Encloses the lungs and mediastinum.
• Provides protection to vital organs.
• Adapts shape to allow for airflow.

Pleura

• Parietal Pleura: Lining inner thoracic wall; serous membrane.
• Visceral Pleura: Covers the lungs.
• Pleural Space: Fluid-filled space reducing friction during breathing.
• Intrapleural Pressure: Decreases during inhalation, maintaining lung expansion.

Breathing Mechanics

• Inspiration: Diaphragm contracts, enlarging thoracic cavity.
• Exhalation: Diaphragm relaxes, reducing thoracic cavity volume.
• Accessory Muscles: Help during forceful inhalation (e.g., sternocleidomastoid, scalenes).
• Passive Expiration: Occurs through recoil during normal breathing.

Lung Structure

• Right Lung: 3 lobes.
• Left Lung: 2 lobes.
• Hilum: Entrance for bronchi, vessels, nerves.

Pulmonary Circulation

• Pulmonary Artery: Carries deoxygenated blood from the heart to lungs for gas exchange.
• Pulmonary Capillaries: Site for oxygen and carbon dioxide exchange.

Nervous Control of Lungs

• Innervated by the autonomic nervous system, influencing respiratory rate and depth through various reflexes.

Airway Histology

• Mucosa: Contains mucus-secreting cells that trap particles.
• Submucosa: Houses bronchial glands and smooth muscle.
• Adventitia: Connective tissue surrounding larger airways.

Alveoli

• Composed of three cell types:
  • Type I Pneumocytes: Main site for gas exchange.
  • Type II Pneumocytes: Produce surfactant to reduce surface tension.
  • Type III Pneumocytes: Macrophages that defend against pathogens.
• Pores of Kohn: Allow collateral ventilation among alveoli.