exchange surfaces and breathing M3.C7

• do small organisms have high or low SA:V?

  high
• small organisms, e.g. bacteria, have a large surface area to volume ratio, so there is a shorter distance from outside the organism to the middle. therefore, simple diffusion across their outer surface meets their exchange needs.
• why do larger organisms require exchange systems?

  higher metabolic rate, smaller SA:V, longer distance from outside of organism to middle of it
• what supports the trachea so it doesn't stick together and close/collapse?

  C-shaped cartilage rings
• what does ciliated epithelium with goblet cells do in the trachea?

  make mucus and sweep it up the trachea
• why is there smooth muscle within the trachea?

  contract if there are harmful substances in the air, constricting the lumen of the trachea, reducing airflow into the lungs. when the smooth muscle relaxes the lumen dilates
• what allows the stretch and recoil of the lumen in the trachea?

  elastic fibres
• what does the trachea split into?

  bronchi
• working out of the lungs, what do bronchioles all join to form?

  bronchi
• working from mouth into lungs, what is the order of the structure of the respiratory system?

  trachea, bronchi, bronchioles, alveoli
• what keeps open the bronchi and bronchioles?

  cartilage
• where are alveoli found?

  end of bronchioles
• where is the site of gas exchange in humans?

  alveoli
• how is the alveoli adapted to be a good location for gaseous exchange?

  large surface area - many alveoli in each lung

  short diffusion distance - alveoli walls and capillary walls are one cell thick

  maintains concentration gradient - each alveolus is surrounded by a capillary network

  good blood supply - surrounded by capillaries
• what cells are the alveoli made up of?

  squamous epithelial cells
• what muscles are involved in ventilation?

  diaphragm, external and internal intercostal muscles
• what is the purpose of ventilation?

  maintain concentration gradient for gas exchange
• inhalation/inspiration process?

  active process, diaphragm contracts and moves down, external intercostal muscles contract moving the ribs up and out, internal intercostal muscles relax. thoracic volume increases, thoracic pressure decreases below atmospheric pressure making a pressure gradient that draws air into lungs to equalise pressure difference
• what does it mean if a process is active?

  uses energy
• what causes ventilation?

  pressure changes in the thoracic cavity
• what are antagonistic muscles?

  muscles that work in opposite directions
• give an example of antagonistic muscles in animals?

  internal and external intercostal muscles
• why is expiration/exhalation a passive process?

  muscles don't contract so energy isn't required
• expiration/exhalation?

  passive process, external intercostal muscles and diaphragm relax moving the ribs down and in, thoracic volume decreases, thoracic pressure increases, air flows out of the lungs to equalize the pressure difference
• when are the internal intercostal muscles most active?

  forced exhalation
• what can we use to measure the volume of air inhaled and exhaled?

  spirometer
• what is vital capacity?

  maximum volume of air an individual can inhale and exhale in one breath
• what is tidal volume?

  volume of air that moves into and out of the lungs with each resting breath
• what is residual volume?

  the volume of air that remains in the lungs so they don't collapse
• what is breathing rate?

  number of breaths per minute
• what is ventilation rate?

  volume of air inhaled per minute
• how do we work out ventilation rate?

  tidal volume * breathing rate
• what does a peak flow meter measure?

  rate at which air can be expelled from lungs
• what 4 features need to be commented on when talking about exchange systems?

  blood supply, concentration gradient, diffusion pathway, surface area
• why are the cartilage rings in the trachea incomplete?

  so food can move down oesophagus behind it
• what do goblet cells do?

  secrete mucus
• do bronchioles have cartilage rings?

  no
• do bronchi have cartilage rings?

  yes
• bronchioles are lined with a thin layer of epithelium for some gas exchange
• the alveoli is where most gas exchange occurs