The Human Respiratory System

Introduction

• The respiratory system facilitates the exchange of gases (oxygen and carbon dioxide).
• It works closely with the circulatory system to deliver oxygen needed for cellular respiration.

Pathway of Air

• Inhalation Process:
  • Air enters through the nasal cavity.
  • Air is warmed, humidified, and filtered using mucus and nasal hairs.
  • Air passes through the pharynx, larynx (voice box), and trachea.
  • The epiglottis prevents food from entering the trachea (food travels down the esophagus).
  • The trachea is supported by cartilage rings and branches into primary bronchi (one for each lung).

Lungs and Bronchial Tree

• Lung Structure:
  • Two lungs: right lung has 3 lobes, left lung has 2 lobes (with a cardiac notch).
• Bronchial Tree:
  • Primary bronchi divide into secondary bronchi, then into tertiary bronchi, and finally into smaller bronchioles.
  • Bronchioles lead to alveolar ducts, which are surrounded by alveolar sacs containing alveoli.
  • Gas Exchange:
    • Alveoli are thin-walled and have a large surface area.
    • They are in direct contact with capillaries for oxygen and carbon dioxide exchange.
    • Red blood cells pick up oxygen and remove carbon dioxide.

Supporting Systems

• Circulatory System: Works with respiratory system for gas exchange.
• Skeletal System: Ribs protect lungs.
• Muscular System: Intercostal muscles, diaphragm, and abdominal wall muscles help in expanding or contracting the thoracic cavity.
• Nervous System: Regulates involuntary breathing using pH as a signal.
  • Increase in carbon dioxide raises H+ concentration, lowering blood pH (more acidic).
  • Brain controls breathing rate and depth to stabilize blood pH at around 7.4.

Other Animal Respiratory Systems

• Different methods of gas exchange in animals (e.g., earthworms use skin, fish use gills, insects use tracheal systems with spiracles).

Respiratory Health

• Understanding the respiratory system aids in treating respiratory illnesses (e.g., asthma, emphysema).
• Careers focused on respiratory health: pulmonologists, respiratory therapists.
• Treatment for conditions like respiratory distress syndrome (RDS) in premature babies using artificial surfactants.

Conclusion

• Surfactants are crucial for alveolar inflation by lowering surface tension.
• Advances in respiratory treatments save lives (e.g., artificial surfactants for premature infants).