Gas exchange

• What is the total lung capacity ?

  The vital capacity added to the residual volume
• what is the residual volume ?

  the volume of air that remains in the lungs after the largest possible exhalation
• what’s the expiratory reserve volume ?

  The expiratory reserve volume is the maximum volume of air that can be exhaled above a normal exhalation
• what’s the inspiration reserve volume?

  the inspiratory reserve volume is the maximum volume of air that can be inhaled above a normal inhalation
• what’s breathing rate ?

  the number of breaths per minute
• what is the Tidal volume

  The tidal volume is the volume of air inhaled and exhaled in an average breath during rest.
• what is vital capacity

  vital capacity is the maximum volume of air that can be inhaled and exhaled
• how do you calculate ventilation rate ?

  by multiplying tidal volume by breathing rate
• What’s the ventilation rate

  The ventilation rate is the volume of air moved into the lungs per minute
• Single-celled organisms have a high surface area to volume ratio.
• how do single-celled organisms exchange gases with their external environment?

  by diffusion across the cell-surface membrane (this is possible because their surface area to volume ratio is high)
• as the size of an organism increases, it’s surface area to volume ratio decreases.
• what needs to be exchanged between an organism and it’s environment ?

  • nutrients (glucose)
  • Respiratory gases (oxygen)
  • Excretory products (urea)
  • heat
• what is an exchange surface ?

  A specialised structure that allows materials to be transferred between cells and an organisms surrounding environment (exchange surfaces always involve plasma membranes)
• key features of specialised exchange surfaces

  • thin layers
  • large surface area
  • surrounded by selectively permeable plasma membranes
  • steep concentration gradient for diffusion, maintained by a transport system
• how does the metabolic rate of an organism affects amount of material it needs to exchange ?

  organisms with higher metabolic rates, need to exchange, more materials

  (they need a higher sa to v ratio and/or specialised exchange system to exchange these substances at a faster rate)
• What is the function of the elastic fibres in alveoli?

  Elastic fibres contain elastin that allows alveoli to stretch when they are full or air and to recoil back to their original shape when air leaves the alveoli.
• The alveolus is a small air sac with a thin wall comprising one layer of squamous epithelium cells, elastic fibres and collagen fibres.
• function of collagen fibres in alveoli?

  collagen fibres contain strong collagen that prevents alveoli from bursting and limits overstretching.
• how does oxygen move between alveoli and blood?

  oxygen diffuses from atmospheric air in the alveolus cavity across the alveoli epithelium into the blood in the pulmonary capillaries. there it binds to haemoglobin in red blood cells.
• key features of capillaries

  1. thin walls - one cell thick so gases only travel short distance
  2. steep diffusion gradient maintained by the movement of blood- increases rate of diffusion
  3. large surface area- increase rate of diffusion
  4. slow movement of blood - gives more time for diffusion
  5. RBC are flat against capillary wall - reduces gas diffusion distance between the rbc and the alveoli
• blood vessels

  pulmonary artery - delivers deoxygenated blood from heart to pulmonary capillaries

  capillaries - co2 diffuses from the capillary blood into the alveoli, and oxygen diffuses from the alveoli into the capillary blood

  pulmonary vein - delivers oxygenated blood from the pulmonary capillaries to the heart
• structures that line trachea and bronchi

  • cartilage- supports the airways & prevents them from collapsing
  • smooth muscle - contracts or relaxes to constrict or dilate the airway and change airflow
  • goblet cells - produce mucus to trap dirt, dust, and microorganisms
  • ciliated epithelial cells- lined with cilia to waft mucus away from the alveoli.

  ( bronchioles contain all except cartilage)
• key features of alveoli

  • thin walls - alveolar epithelium is one cell thick so gases only travel a short distance
  • steep diffusion gradient maintained by ventilation of lungs- increased diffusion rate
  • large SA- increases diffusion rate
  • partially permeable - only specific gases can move across the alveolar epithelium
  • most inner surface - water allows gases to dissolve and lung surfactant helps alveoli remain inflated