Human Gas Exchange

• Why do mammals have a high oxygen demand?

  They maintain a constant body temperature
• How do mammals obtain oxygen?

  From the air via their lungs
• What role do the ribs play in the respiratory system?

  They protect the lungs and assist in breathing using intercostal muscles
• What is the name of the tube that air passes through after the nasal cavity?

  The trachea
• What are the two key adaptations of the trachea?

  Cartilage and ciliated epithelia
• What prevents the walls of the trachea from collapsing?

  Cartilage
• Why does the trachea have a c-shape cartilage structure?

  To allow food to pass down the esophagus
• What do goblet cells in the trachea secrete?

  Mucus
• What is the function of cilia on epithelial cells in the trachea?

  To move mucus to the throat
• What do the bronchi carry air into?

  Each of the lungs
• What do bronchioles contain that allows them to widen?

  Smooth muscle
• What are alveoli the sites of?

  Gas exchange
• How are alveoli adapted for gas exchange?

  They provide a large surface area
• What covers the internal walls of the alveoli?

  A thin layer of moisture
• How does oxygen enter the red blood cells from the alveoli?

  It diffuses into the red blood cells
• What helps maintain a steep concentration gradient for oxygen?

  The extensive capillary network
• What ensures a rapid rate of diffusion of gases in the alveoli?

  A high concentration of oxygen and low carbon dioxide
• What are the adaptations of alveoli for efficient gas exchange?

  • Hundreds of millions of alveoli provide a large surface area
  • Walls are one cell thick for short diffusion distance
  • Narrow capillaries bring red blood cells close to alveoli
  • Extensive capillary network maintains steep concentration gradients
• What is the overall structure of the mammalian gas exchange system?

  1. Nasal cavity: warms and moistens air
  2. Trachea: supported by cartilage, lined with ciliated epithelia
  3. Bronchi: carry air into lungs, contain cartilage and ciliated epithelia
  4. Bronchioles: progressively narrower airways with smooth muscle
  5. Alveoli: sites of gas exchange, covered with capillaries