Exchange Surfaces

• Why do organisms need specialised exchange surfaces?

  Due to size and surface area to volume ratio
• How do single-celled organisms exchange substances?

  Substances easily enter due to short distance
• Why do multicellular organisms require specialised exchange surfaces?

  To efficiently exchange gases due to larger distances
• What are features of an efficient exchange surface?

  Large surface area and thin structure
• Why is a good blood supply important for exchange surfaces?

  It maintains a steep concentration gradient
• What is the role of the lungs in mammals?

  Gas exchange with a large surface area
• What protects the lungs in the chest cavity?

  The rib cage surrounds and protects them
• What prevents friction between the rib cage and lungs?

  A lubricating substance is secreted
• What is the function of intercostal muscles?

  To raise and lower the rib cage
• What separates the lungs from the abdomen?

  The diaphragm
• How does air enter the lungs?

  Through the nose, trachea, bronchi, and bronchioles
• Where does gaseous exchange occur in mammals?

  In the walls of the alveoli
• What keeps the airways open?

  Rings of cartilage
• How are the trachea and bronchi similar?

  Both have similar structural composition
• What is the composition of the trachea and bronchi walls?

  Cartilage, glandular tissue, elastic fibres
• What is the role of goblet cells?

  To secrete mucus that traps bacteria
• How do elastic fibres function in the respiratory system?

  They stretch during inhalation and recoil during exhalation
• What is ventilation in the context of respiration?

  The flow of air in and out of the alveoli
• What happens during inspiration?

  External intercostal muscles contract and diaphragm flattens
• What occurs during expiration?

  Internal intercostal muscles contract and diaphragm relaxes
• What is a spirometer used for?

  To measure lung volume
• What is vital capacity?

  The maximum air volume inhaled or exhaled
• What is tidal volume?

  The air volume breathed at rest
• How is breathing rate calculated?

  By counting peaks or troughs in a minute
• What is residual volume?

  The air volume always present in the lungs
• What is inspiratory reserve volume?

  The additional air volume inhaled during exercise
• What is expiratory reserve volume?

  The additional air volume exhaled beyond tidal volume
• Why do fish need specialised exchange surfaces?

  Due to small surface area to volume ratio
• How many pairs of gills do bony fish have?

  Four pairs
• What is the function of gill filaments?

  They participate in gas exchange
• How does blood flow across lamellae in fish gills?

  In a counter current direction
• What happens to gill projections when fish are out of water?

  They stick together and cannot function
• How does ventilation occur in fish?

  By opening mouth and lowering buccal cavity
• What role do spiracles play in insects?

  They allow gas exchange directly to tissues
• What is the function of tracheoles in insects?

  To supply oxygen directly to cells
• What is the purpose of tracheal fluid in insects?

  To allow gases to dissolve and diffuse
• How do spiracles help insects conserve water?

  They can be opened and closed