Lecture Notes: The Human Respiratory System

Introduction

• The human respiratory system is responsible for the exchange of gases.
• It should not be confused with cellular respiration, which occurs within cells to produce ATP, using oxygen, and releasing carbon dioxide as a byproduct.
• The respiratory system works alongside the circulatory system to transport oxygen to cells and expel carbon dioxide from the body.

Pathway of Air

1. Nasal Cavity
   • Air is warmed, humidified, and filtered.
   • Mucus and nasal hairs (cilia) play a role in this process.
2. Pharynx
   • Junction for food and air.
3. Larynx (Voice Box)
4. Trachea
   • Supported by rings of cartilage to remain open.
   • Air travels through this tube.
5. Primary Bronchi
   • Branches into the lungs.
6. Lungs
   • Right lung has three lobes, left lung has two lobes with a cardiac notch.
7. Smaller Air Passages
   • Primary bronchi divides into secondary bronchi, then tertiary bronchi, and further into bronchioles.
   • Structure resembles an upside-down tree.

Gas Exchange

• Occurs in the alveoli which are surrounded by capillaries.
• Alveoli have a large surface area and thin walls for efficient gas exchange.
• Oxygen is picked up by red blood cells; carbon dioxide is brought to be exhaled.

Interaction with Other Systems

• Circulatory System: Works closely for gas exchange.
• Skeletal System: Ribs protect the lungs.
• Muscular System: Includes diaphragm, intercostal muscles, and abdominal wall muscles to facilitate breathing.
• Nervous System: Regulates involuntary breathing through pH detection. Increase in carbon dioxide leads to increased H+ concentration, lowering blood pH, signaling the brain to adjust breathing.

pH and Breathing Rate

• Blood pH is ideally around 7.4.
• Changes in blood pH can trigger changes in respiration to maintain homeostasis.
• Exercise increases breathing rate and depth.

Comparative Respiratory Systems

• Different organisms have various systems for gas exchange:
  • Earthworms: Skin
  • Fish: Gills
  • Insects: Tracheal system and spiracles

Respiratory Health and Careers

• Understanding the respiratory system aids in treating illnesses such as asthma and emphysema.
• Respiratory therapists and pulmonologists specialize in these areas.
• Respiratory distress syndrome (RDS) in premature infants is treated with artificial surfactants.

Surfactant and Its Role

• Surfactant, made by type 2 alveolar cells, reduces surface tension in alveoli preventing collapse.
• Important in treating premature babies who lack sufficient surfactant.

Conclusion

• The study of the respiratory system provides insights into understanding and treating respiratory conditions.
• Continued curiosity is encouraged to learn more about these systems.