Lecture Notes: The Human Respiratory System

Introduction

• The human respiratory system allows for the exchange of gases.
• Distinction between respiratory system and cellular respiration:
  • Cellular respiration: process by which cells use oxygen to make ATP and produce carbon dioxide as a byproduct.
  • Respiratory system: takes in oxygen and expels carbon dioxide.

Pathway of Air Through the Respiratory System

1. Nasal Cavity
   • Air is warmed, humidified, and filtered.
   • Uses mucus and nasal hairs (visible and microscopic cilia).
2. Pharynx
   • Junction of food and air.
3. Larynx (Voice box)
4. Trachea
   • Composed of rings of cartilage for support.
5. Primary Bronchi
   • Two bronchi, one for each lung.
6. Lungs
   • Two lungs: right lung has 3 lobes, left lung has 2 lobes (cardiac notch for the heart).
7. Bronchi Division
   • Primary bronchi → Secondary bronchi → Tertiary bronchi → Smaller bronchioles.
   • Structure resembles an upside-down tree.
8. Alveolar Ducts and Sacs
   • Alveolar sacs contain alveoli, where gas exchange occurs.
   • Alveoli: thin-walled, large surface area, direct contact with capillaries.

Gas Exchange Process

• Role of Circulatory System:
  • Red blood cells pick up inhaled oxygen and deliver it throughout the body.
  • Remove carbon dioxide for exhalation.

Interactions with Other Body Systems

• Skeletal System: Ribs protect lungs.
• Muscular System:
  • Intercostal muscles, diaphragm, and abdominal muscles assist in breathing.
• Nervous System:
  • Regulates breathing, responds to changes in blood carbon dioxide levels and pH.
  • Increase in carbon dioxide lowers blood pH, prompting the brain to adjust breathing rate.

Homeostasis and Breathing Control

• Normal blood pH is around 7.4.
• Breathing rate and depth increase during exercise.

Other Organisms' Gas Exchange Methods

• Earthworms: Gas exchange through skin.
• Fish: Use gills.
• Insects: Have a tracheal system with spiracles.

Understanding Respiratory Health

• Knowledge of the respiratory system aids in treating respiratory illnesses.
• Careers: Pulmonologists and respiratory therapists.
  • Treatment of conditions like asthma, emphysema, and respiratory distress in premature infants.

Alveoli and Surfactant

• Alveoli need surfactant to reduce surface tension and prevent collapse.
• Type 2 alveolar cells produce surfactant (phospholipids and proteins).
• Premature infants may lack sufficient surfactant, risking respiratory distress syndrome (RDS).
• Artificial surfactants can treat and save lives of premature infants.

Conclusion

• Continuous curiosity about the respiratory system and its complexities is encouraged.