Overview
This lecture explains the structure and function of the lungs, focusing on how alveoli are adapted for efficient gas exchange to support cellular respiration.
Structure and Function of the Lungs
- The lungs obtain oxygen from the air and transfer it into the bloodstream for body use.
- Air enters through the mouth or nose, travels down the trachea (windpipe), into the bronchi, then bronchioles.
- Air finally reaches tiny sacs called alveoli, which are the primary site of gas exchange.
Alveoli and Gas Exchange
- Alveoli are composed of a single thin cell layer, creating a short diffusion path for gases.
- Hundreds of millions of alveoli provide a large surface area, enhancing gas exchange efficiency.
- Alveolar walls are moist, allowing gases to dissolve and diffuse faster.
- Oxygen in alveoli moves down its concentration gradient into oxygen-poor blood in capillaries.
- Carbon dioxide in higher concentration in the blood diffuses into alveoli and is exhaled.
- Oxygen is transported by hemoglobin in red blood cells, while carbon dioxide is dissolved in blood plasma.
- Blood flow through capillaries is continuous, maintaining constant gas exchange.
Breathing Rate Calculation
- Breathing rate can be calculated by dividing the number of breaths taken by the time in minutes.
- Example: 42 breaths in 3 minutes equals 14 breaths per minute.
Key Terms & Definitions
- Alveoli — tiny air sacs in the lungs where gas exchange occurs.
- Trachea — the windpipe; main airway to the lungs.
- Bronchi/Bronchioles — branching air passages leading from the trachea to alveoli.
- Diffusion — movement of molecules from high to low concentration.
- Hemoglobin — protein in red blood cells that carries oxygen.
- Plasma — liquid component of blood that carries dissolved substances.
Action Items / Next Steps
- Practice calculating breathing rate using sample data.
- Review the structure and function of alveoli and associated blood vessels.