humans

• The trachea has 3 layers: an outer layer of cartilage, a middle layer of smooth muscles and an in layer of elastic fibres
• The trachea Is coated in ciliated epithelium and goblet cells to keep the trachea clean
• When we breath in, external intercostal muscles contract
• When we breath out, internal intercostal muscles contract
• Pulmonary ventilation rate (pvr) is the total volume of air moved into the lungs in 1 min
• Tidal volume is the volume of air of each breath when body is at rest
• Breathing rate is how many breaths a person takes per min
• PVR=tidal vol X breathing rate
• Absorption of amino acids: NA+ removed from cell by NA+, K+ pump, amino acids removed from cell by facilitated diffusion, this maintains a concentration gradient, NA+ and amino acids bind to co-transport protein which carries them across membrane
• give one adaptation of the alveolar epithelium in the lungs- it is very thin so there is only a short diffusion distance
• features of a good exchange system:

  • large SA
  • short diffusion distance
  • concentration gradient
• process of breathing (filling lungs with air):

  1. Diaphragm contracts and external intercostal muscles contract
  2. Causes volume increase and pressure decrease;
  3. Air moves down a pressure gradient into lungs
• High metabolic rate = more materials exchanged - Smaller organisms have a higher metabolic rate per unit of body mass