gas exchange

• Multicellular organisms require specialized exchange surfaces for efficient gas exchange.
• What is a key feature of an efficient exchange surface for maintaining a steep gradient?

  Good blood supply
• Fish have a small surface area to volume ratio for gas exchange.
• How many pairs of gills do bony fish have?

  Four
• Blood and water flow across the lamellae in a counter-current direction to maintain a steep diffusion gradient.
• Counter-current flow in fish gills ensures that the maximum amount of oxygen diffuses into the blood.
• Steps in fish ventilation

  1️⃣ Fish opens its mouth

  2️⃣ Lowering of the buccal cavity floor

  3️⃣ Water flows into the buccal cavity

  4️⃣ Fish closes its mouth

  5️⃣ Buccal cavity floor raises

  6️⃣ Water is forced over gill filaments
• Match the structure with its function in the mammalian gaseous exchange system:

  Cartilage ↔️ Supports trachea and bronchi

  Ciliated epithelium ↔️ Moves mucus towards the throat

  Goblet cells ↔️ Secrete mucus to trap bacteria

  Smooth muscle ↔️ Controls airway diameter
• The flow of air in and out of the alveoli is referred to as ventilation.
• Steps in inspiration during breathing

  1️⃣ External intercostal muscles contract

  2️⃣ Diaphragm flattens

  3️⃣ Volume inside thorax increases

  4️⃣ Pressure inside lungs decreases

  5️⃣ Air is forced into the lungs
• During expiration, the diaphragm relaxes and raises upwards, increasing the pressure inside the thorax.
• What device is used to measure lung volume?

  Spirometer
• The maximum volume of air that can be inhaled or exhaled in a single breath is called the vital capacity.
• Where are the lungs located in the body?

  Chest cavity
• The trachea is held open by incomplete rings of cartilage.
• Alveoli are adapted for gas exchange because they are surrounded by capillaries.
• What is the volume of air breathed in and out at each breath at rest called?

  Tidal volume
• What is another name for the windpipe?

  Trachea

  
• Alveoli are located at the end of bronchioles

  
• where does gas exchange take place

  Alveoli
• how are alveoli adapted for transport?


  1. good blood supply - maintains a steep concentration gradient
  2. very thin(one cell thick)
  3. surrounded by capillaries - reduces diffusion pathway
  4. many alveoli - large surface area
• define ventilation

  the flow of air in and our of the alveoli
• how many stages of ventilation are there & define them

  2 stages of ventilation:

  • inspiration
  • expiration
• explain how air is moved out of the lungs (expiration)

  1. the internal intercostal muscles contract, external muscles relax
  2. the rib cage is lowered
  3. diaphragm relaxes, raises upwards
  4. the volume inside the thorax is decreased, increasing the pressure
  5. air is forced out of the lungs.
• name the two layers of muscles between the ribs

  1. internal intercostal muscles
  2. external intercostal muscles
• describe the intercostal muscles movement for ventilation

  • air moves in when the external intercostal muscles contract and internal intercostal muscles relax.
  • Air moves out when the external intercostal muscles relax and internal intercostal muscles contract
• define tidal volume

  the volume of air breathed in or out during a normal breath
• define residual volume

  the volume of air that always remain in the lungs, after maximal exhalation
• what happens when both the internal intercostal muscles & diaphragm contract

  the volume of air inside the thorax ( chest cavity) increases, decreasing the pressure inside
• Inhalation

  the difference between the pressure inside the lungs & atmospheric (air outside of the body) pressure creates a gradient, this causes the air to be forced into the lungs
• what is a spirometer

  a spirometer is a device that is used to measure lung volume
• what does a spirometer measure

  lung volume