Human Respiratory System - Key Concepts

Introduction

• Respiratory system includes more than just oxygen: water vapor, gases like krypton, and particles.
• Upper airways provide protection against unwanted particles.

Protective Mechanisms of Upper Airways

• Nasal Hair: Stops large dirt particles/insects.
• Nasal Mucosa: Traps small particles.
• Ciliated Cells: Wave-like movements push mucus towards the pharynx.
  • Mucociliary Clearance: Small particles swallowed with mucus.

Upper Airways Functions

• Warm and Moistens Air: Nasal and oral cavities.
• Epiglottis: Prevents food/liquid from entering the lower respiratory tract by closing the larynx during swallowing.

Structure of the Respiratory System

• Trachea: Reinforced by hyaline cartilage rings; branches into main bronchi.
• Main Bronchi: Lead to lungs; left lung has 2 lobes, right lung has 3 lobes.
• Lobes and Segments: Right lung - 3 lobes with 10 segments; supplies air and blood separately.
• Bronchial Tree: Main bronchi branch into finer tubes ending in alveoli.
• Alveoli: Tiny air sacs (~300-400 million); site of gas exchange.

Gas Exchange

• Alveolar Structure: Type 1 pneumocytes allow oxygen and carbon dioxide diffusion.
• Blood Vessel Network: Covers alveoli for oxygenation of blood and CO2 release.
• Erythrocytes: Transport oxygen with iron binding.
• Diffusion: Balances gas concentration differences.

Mechanism of Breathing

• Muscles Involved: Neck, ribs, and diaphragm.
• Chest Breathing:
  • Bucket-handle Motion: Rib rotation increases chest volume.
  • Pump-handle Motion: Sternum rotation aids volume change.
• Diaphragmatic Breathing: Natural resting breathing.
  • Diaphragm movement increases/decreases lung volume.

Pleura and Lung Movement

• Pleura: Allows lung movement against the chest wall.
  • Inner Pleura: Covers lungs.
  • Outer Pleura: Lines ribcage and diaphragm.
  • Pleural Cavity: Space between pleura layers facilitates movement.