in humans

• describe the gross structure of the human gas exchange system

  trachea, bronchus, bronchioles, alveoli
• where are alveoli found?

  at the end of the bronchioles
• lungs

  central organs in the mammalian respiratory system
• what is an organ?

  a collection of tissues working together for a similar function
• trachea

  has rings of cartilage, goblet cells and ciliated epithelial cells
• trachea - rings of cartilage

  prevent collapse from the pressure changes when breathing in and out
• trachea - goblet cells

  produce mucus which traps microbes/pathogens
• trachea - ciliated epithelial cells

  waft the mucus up to your mouth to swallow down to stomach or spit out
• bronchi/bronchus

  rings of cartilage, goblet cells and ciliated epithelial cells
• bronchi - rings of cartilage

  prevent collapse
• bronchi - ciliated epithelial cells

  waft mucus up to be swallowed or spat out
• bronchi - goblet cells

  produce mucus to trap microbes/ pathogens
• bronchioles

  highly branched and end in alveoli
• alveoli

  where gas exchange happens
• essential features of alveolar epithelium

  many alveoli

  each alveoli close to a capillary

  thin walls

  specialised epithelial cells

  alveoli made of elastic fibres

  constant ventilation / circulation
• many alveoli -

  large SA for diffusion
• each alveoli close to a capillary -

  short diffusion pathway
• thin walls -

  1 cell thick

  short diffusion distance
• specialised epithelial cells -

  squamous

  thinner = short diffusion distance
• alveoli made of elastic fibres -

  allows to stretch and recoil to get air in and force it back out
• constant ventilation and circulation -

  maintains a concentration gradient
• pathway of oxygen through the epithelium -

  through the epithelial cell

  to the endothelial cell of capillary

  into RBC
• carbon dioxide diffuses in the ...

  ...opposite direction
• pathway of carbon dioxide through an epithelium -

  from the RBC

  to the endothelial cells in the capillary

  to the epithelial cells

  out
• structures involved in ventilation -

  ribs, diaphragm, external and internal intercostal muscles
• ventilation - inspiration

  diaphragm contracts and flattens

  external intercostal contract

  ribcage pulled up and out

  volume of the thorax increases

  pressure decreases

  air moves from high to low pressure
• what does diaphragm do in inspiration?

  contracts and flattens
• what do intercostal muscles do in inspiration?

  contract
• what does the ribcage do in inspiration?

  pulled up and out
• what does the thorax do in inspiration?

  volume of it increases
• is the pressure high or low in inspiration?

  low
• ventilation - expiration

  diaphragm relaxes and moves up

  external intercostal relax

  ribcage moved down and back

  volume of the thorax decreases

  pressure increases

  air moves from high to low pressure
• what does diaphragm do in expiration?

  relaxes and moves up
• what do external intercostal muscles do in expiration?

  relax
• what does ribcage do in expiration?

  moved down and back
• what does thorax do in expiration?

  the volume decreases
• is the pressure high or low in expiration?

  high
• how to calculate pulmonary ventilation rate?

  Tidal volume x breathing rate
• what is tidal volume?

  volume of air taken in during each breath at rest
• what is breathing rate?

  number of inhalations per minute