Overview
This lecture explains the structure and function of the human respiratory system, its interactions with other body systems, and the importance of alveoli and surfactant in gas exchange.
Structure of the Respiratory System
- The respiratory system enables gas exchange: oxygen in, carbon dioxide out.
- Air travels: nasal cavity β pharynx β larynx β trachea β primary bronchi β secondary bronchi β tertiary bronchi β bronchioles.
- The trachea is supported by cartilage rings to stay open for airflow.
- Lungs are divided into lobes: three on the right, two on the left (with a cardiac notch for the heart).
- Bronchioles end in alveolar ducts leading to alveolar sacs, which contain alveoli for gas exchange.
Gas Exchange and Alveoli
- Alveoli are thin-walled sacs with high surface area, surrounded by capillaries for efficient gas exchange.
- Oxygen diffuses from alveoli to capillaries; carbon dioxide moves from blood to alveoli to be exhaled.
- Surfactant, produced by type 2 alveolar cells, lowers surface tension in alveoli, preventing their collapse.
Coordination with Other Body Systems
- Circulatory system transports gases to and from the lungs.
- Skeletal system (ribs) protects the lungs, while the muscular system (diaphragm, intercostal, and abdominal muscles) enables breathing movements.
- Nervous system regulates breathing, mostly involuntarily, in response to blood pH and COβ levels.
Regulation of Breathing and Homeostasis
- Increased COβ in blood lowers pH (more acidic), which is detected by the brain.
- Brain signals muscles to increase breathing rate and depth, maintaining pH around 7.4 (homeostasis).
Respiratory System in Other Organisms
- Earthworms exchange gases through skin; fish use gills; insects use a tracheal system with spiracles.
Clinical Relevance
- Understanding the respiratory system helps treat respiratory illnesses; pulmonologists and respiratory therapists specialize in these treatments.
- Premature babies may lack surfactant, risking respiratory distress syndrome (RDS); artificial surfactant can treat this.
Key Terms & Definitions
- Alveoli β tiny air sacs in the lungs where gas exchange occurs.
- Surfactant β a substance produced by alveolar cells that reduces surface tension, preventing alveolar collapse.
- Homeostasis β maintaining stable internal conditions (like blood pH).
- Intercostal muscles β muscles between ribs involved in breathing.
- Diaphragm β major muscle beneath lungs responsible for inhalation.
- pH β a scale measuring acidity/basicity based on hydrogen ion concentration.
- Respiratory distress syndrome (RDS) β a condition where lack of surfactant leads to alveolar collapse.
Action Items / Next Steps
- Review chemistry of how COβ affects blood pH.
- Watch related videos on water properties and cellular respiration for deeper understanding.
- Explore how other organisms perform gas exchange.