Human Respiratory System

Introduction to Respiratory System

• Oxygen is crucial for human survival.
• Air we breathe contains water and other gases (e.g., Krypton, radon).
• Air includes large and small particles that should not enter lower respiratory tract.

Protective Mechanisms of Upper Airways

• Nasal Cavity:
  • Large particles/insects stopped by nasal hair.
  • Small particles trapped by nasal mucosa.
  • Ciliated cells move in wave-like manner to push nasal mucus towards pharynx.
  • Mucociliary Clearance: Process where small particles trapped by nasal mucus are swallowed.
• Warming and Moistening:
  • Upper airways warm and moisten inspired air.
• Epiglottis Function:
  • Prevents food/liquid from entering lower respiratory tract by closing larynx during swallowing.

Structure of the Respiratory System

• Trachea:
  • Located below larynx, reinforced by hyaline cartilage rings.
• Bronchi and Lungs:
  • Trachea branches into two main bronchi -> left and right lungs.
  • Left lung: 2 lobes, Right lung: 3 lobes.
  • Main bronchi form trunks for bronchial tree.
  • Lungs have lobes and segments (right lung has 10 segments).
• Alveoli:
  • Site of gas exchange.
  • Estimated 300-400 million alveoli in humans.
  • Thin Type 1 pneumocytes cells for diffusion.

Process of Gas Exchange

• Bronchi and Bronchioles:
  • Bronchi: Large branches with cartilage.
  • Bronchioles: Thin branches at end, surrounded by elastic fibers and smooth muscle.
• Alveolar Structure:
  • Alveoli grouped in sacs supplied by alveolar ducts.
  • Covered with network of blood vessels.
• Diffusion Process:
  • Oxygen diffuses into blood, carbon dioxide out into alveoli.
  • Balance of concentration differences through diffusion.

Respiratory Muscles

• Muscles Involved in Breathing:
  • Neck muscles: Raise/fix sternum and ribs.
  • Rib muscles: Raise/lower ribs (bucket handle motion).
• Diaphragm:
  • Main muscle for breathing.
  • Responsible for chest volume changes and pressure differences (inhalation/exhalation).

Breathing Mechanics

• Chest Breathing:
  • Involves neck and rib muscles causing rib rotation and chest volume increase.
  • Pump handle motion of sternum increases and decreases lung volume.
• Diaphragmatic Breathing:
  • Diaphragm rises and lowers, breathing naturally.
  • Pleura Function:
    • Inner pleura covers lungs, outer lines rib cage and diaphragm.
    • Allows smooth lung movement via pleural cavity.