Lecture Notes on Respiration - November 15

Introduction

• Date: Monday, November 15
• Continuation of the lecture on respiration
• PowerPoint presentation focused on the structure and function of the respiratory system

Overview of the Bronchial Tree

• Trachea: Single windpipe of the respiratory system, supported by cartilage
• Primary Bronchi: Trachea splits into two primary bronchi (right and left), corresponding to two lungs
• Secondary Bronchi:
  • Right lung: 3 secondary bronchi (for 3 lobes)
  • Left lung: 2 secondary bronchi (for 2 lobes)
  • Difference due to heart position, creating a cardiac notch on the left lung
• Tertiary Bronchi: Further subdivisions into bronchopulmonary segments
• Bronchioles: Lead to lobules, filled with alveoli and alveolar sacs

Surgical Implications

• Tumor detection in the lung is easier due to compartmentalization
• Early detection allows for removal of specific segments or lobes, preserving lung function

Alveoli and Gas Exchange

• Structure:
  • Made of simple squamous epithelium (pneumocyte type 1 cells)
  • Surrounded by capillaries for gas exchange
  • Provides large surface area for oxygen absorption
• Function:
  • Oxygen enters blood, carbon dioxide exits
  • Alveolar macrophages (dust cells) clean the area

Changes in the Bronchial Tree

• Size Reduction: Tubes get smaller in diameter
• Cartilage: Decreases, eventually replaced by smooth muscle
• Cell Type Transition:
  • Starts with pseudostratified columnar epithelium
  • Transitions to simple columnar, then cuboidal, and finally simple squamous as tubes get smaller
• Cilia: Decrease and eventually disappear in the smallest passageways

Pulmonary Ventilation

• Inspiration (Inhalation):
  • Diaphragm contracts and moves downward
  • Ribs expand and go up and outward via external intercostal muscles
  • Result: Lower intra-pulmonary pressure, air enters lungs
• Expiration (Exhalation):
  • Diaphragm relaxes and moves upward
  • Ribs move inward and downward
  • Higher intra-pulmonary pressure, air exits lungs
• Supplemental Muscles:
  • Inhaling: Sternocleidomastoid, scalenes, pectoralis minor, serratus anterior
  • Exhaling (forceful): Internal intercostals, transverse thoracics, abdominal muscles

Respiratory Membrane

• Made up of alveolar epithelium, capillary endothelium, and basal lamina
• Thin membrane facilitates gas exchange

Smoking Effects

• Nicotine: Chemical entering bloodstream, causes addiction
• Tars: Coats alveoli, hindering gas exchange, leads to smokers cough
• Macrophages: Overworked due to excess dust and particles

Additional Notes

• Premature babies lack surfactant, making breathing difficult
• Medical advancements have improved survival rates of preemies

Closing

• Next lecture will continue with the physiology of breathing
• Review materials on diaphragm and intercostal muscle function for better understanding of breathing mechanics

These notes summarize the key points from the lecture on respiration. Review these sections for a deeper understanding of the respiratory system and its functions.