Gas exchange in humans

• What is the primary function of the lungs in humans?

  To facilitate gas exchange by taking in oxygen and expelling carbon dioxide
• Why do humans need to get oxygen into the blood?

  For respiration, which is essential for energy production
• What is the term used for the process of moving air in and out of the lungs?

  Ventilation
• What are the main structures involved in the gas exchange system in humans?

  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
  • Ribcage
  • Intercostal muscles
  • Diaphragm
• What happens to the trachea during inhalation?

  It splits into two bronchi, one leading to each lung
• What are bronchioles?


  Smaller tubes that branch off from the bronchi and end in alveoli
• What are the small air sacs in the lungs called?

  Alveoli
• What role do the ribcage, intercostal muscles, and diaphragm play in ventilation?


  They work together to move air in and out of the lungs
• What are the two phases of ventilation?

  • Inspiration (breathing in)
  • Expiration (breathing out)
• What happens during inspiration?

  The external intercostal and diaphragm muscles contract, increasing thoracic cavity volume
• How does the pressure change in the thoracic cavity during inspiration?

  The pressure decreases to below atmospheric pressure
• What is the driving force for air to flow into the lungs during inspiration?

  Air flows from an area of higher pressure to an area of lower pressure
• Is expiration an active or passive process?

  Normal expiration is a passive process
• What happens during forced expiration?

  The internal intercostal muscles contract, pulling the ribcage further down and in
• What are the adaptations of the alveoli for efficient gas exchange?

  • Alveolar epithelium is one cell thick
  • Large surface area due to numerous alveoli
  • Steep concentration gradient of oxygen and carbon dioxide
• What is the role of capillaries in gas exchange?

  Capillaries surround the alveoli and facilitate the exchange of gases
• How does oxygen move from the alveoli to the blood?

  Oxygen diffuses across the alveolar epithelium and the capillary endothelium into the blood
• What happens to carbon dioxide during gas exchange?

  Carbon dioxide diffuses from the blood into the alveoli and is exhaled
• What is the process of gas exchange in the alveoli?

  1. Oxygen enters the alveoli from the trachea and bronchi.
  2. Oxygen diffuses across the alveolar epithelium into the capillaries.
  3. Carbon dioxide diffuses from the blood into the alveoli.
  4. Carbon dioxide is exhaled.
• What is the significance of the large surface area of the alveoli?

  It allows for a greater rate of gas exchange
• How is the concentration gradient maintained in the alveoli?

  By the continuous flow of blood and ventilation
• What is the relationship between the structure of the alveoli and their function?

  The thin walls and large surface area of alveoli facilitate efficient gas exchange
• What is the role of the diaphragm in breathing?

  The diaphragm contracts and relaxes to change the volume of the thoracic cavity
• What is the difference between normal expiration and forced expiration?

  Normal expiration is passive, while forced expiration requires muscle contraction
• What is the significance of the antagonistic action of intercostal muscles during forced expiration?

  It allows for a greater reduction in thoracic cavity volume
• What are the warm-up questions related to the gas exchange system?

  1. Describe the structure of the human gas exchange system.
  2. How is normal expiration different from forced expiration?
  3. Describe the movement of carbon dioxide and oxygen across the alveolar epithelium.
• What are the exam questions related to gas exchange in humans?

  1. Describe two ways in which alveoli are adapted for efficient gas exchange.
  2. Describe the process of inspiration.