Lecture on Breathing Mechanics

Introduction

• Discussed breathing processes: Inhalation and exhalation
• Importance of volume changes in breathing
• Focus on the mechanics behind these changes

The Sternum and Rib Connection

• Sternum (Breastbone):

  • Located in the center of the chest
  • Technical name: Sternum
  • Ribs attach to the sternum

• Ribs:

  • Total: 24 ribs (12 pairs)
  • 7 pairs directly attached to the sternum

Intercostal Muscles

• Location: Between the ribs
• Function: Enable expansion and contraction of the chest
• Control:
  • Controlled by nerves
  • Contract when instructed by the brain
• Importance: Facilitate outward movement of the ribs during inhalation

The Diaphragm

• Shape and Location:
  • Dome-shaped muscle
  • Forms the floor of the chest cavity
• Function During Inhalation:
  • Contracts and moves downward, flattening
  • Leads to expansion of the lungs and chest cavity

Lung Expansion

• Ribs move out
• Diaphragm moves down
• Alveoli (air sacs):
  • Expansion corresponds to increased lung volume
  • Approximately 500 million alveoli in the lungs
  • Alveoli surrounded by an elastic protein called elastin

Elastic Properties of Alveoli

• Elastin:
  • Acts like a rubber band
  • Stretches during inhalation
  • Facilitates alveolar expansion

Inhalation versus Exhalation

• Inhalation:

  • Muscles (Intercostal and Diaphragm) contract
  • Volume increases
  • Requires chemical energy (ATP)

• Exhalation:

  • Muscles relax
  • Elastin helps alveoli return to original size
  • Volume decreases
  • Driven by elastic potential energy

Summary

• Breathing involves intricate coordination of muscles and elasticity
• Inhalation requires energy; exhalation relies on stored elastic energy
• Ensures efficient air exchange and lung function