Lungs

• Why are the lungs inside the body?

  Air isn't dense enough to support them, they would lose water and dry out.
• What is the trachea?

  A wall made of muscle so are flexible airways, they are also supported by rings of cartilage which prevent it from collapsing.
• Why are cartilage rings C-shaped?

  If they were circle, they would have fixed diameters so would not be able to expand when we breathe in to allow more air in.
• What is the lining of the trachea made of?

  -Goblet cells to produce mucus that traps dirt and microorganisms.

  -Ciliated epithelium to move mucus up to the throat, down the oesophagus into the stomach.
• What are the bronchi?

  The bronchi are the main airways that branch off from the trachea and lead into the lungs. They produce mucus and have cilia, larger bronchi are supported by cartilage.
• What are bronchioles?


  Branching sun divisions on the bronchi and have muscular walls lined with epithelium cells. The muscle allows bronchioles to constrict-control flow of air in and out of alveoli.
• What are alveoli?


  Tiny air sacs (100-300 micrometer) made of collagen, elastic fibres and lined with epithelium and are the surface of gas exchange. Elastic fibres allow alveoli to stretch and spring back.
• What is Ficks law?

  The law that describes the diffusion of gases across a membrane.

  Rate of diffusion = (surface area x differ concentration) /

  length of diffusion path.
• How does the role of the alveoli relate to Fick's Law?

  Large surface area and short diffusion pathway.
• What happens when you inhale?

  • Inhaling is an active action
  • The external intercostal muscles contract causing the ribcage to move up and out.
  • As the diaphragm contracts, it also flattens.
  • This means the volume of thorax increases and pressure decreases.
  • Therefore a pressure gradient is made and air enters down the pressure gradient.
• What happens when you exhale?

  • Exhaling when resting is a passive actions.
  • The external intercostal muscles relax and the ribcage moves down and in because the tissue is elastic.
  • The volume of thorax decreases and the pressure increases.
  • This creates a pressure gradient between atmosphere and thorax. so air leaves down the pressure gradient.