respiratory system

• Respiratory system


  Structure and function

  
• Nasal cavity


  • Hair traps dust, which is sneezed out
  • Air is warmed and filtered to provide optimum conditions for gaseous exchange
• Pharynx


  • Where the nasal cavity and the oral cavity combine
  • Allows for the movement of air, food and liquid (the epiglottis is used to close off the air way when swallowing)

  
• Larynx


  Also known as the voice box, is used to make sound and to talk
• Trachea


  • Main air pipe that brings air down to the lungs
  • Splits into two main bronchi or bronchus, which continue to branch down to bronchioles
  • Bronchioles bring the air to the alveoli which have a very large porous surface (has pores or holes in it for the exchange of gas), which are lined with fluid
  • Each alveoli is surrounded by a mesh of capillaries to allow for gas exchange into the circulatory system

  
• Inspiration


  1. Diaphragm, intercostals, pectorals are contracted

  2. Decrease in air pressure within lungs

  3. Diaphragm contracts and flattens

  4. External intercostal muscles lift ribs up and out

  5. Increases volume of chest cavity and decreases the air pressure in the lungs

  6. Air rushes into the lungs via the air passages
• Expiration


  1. Diaphragm relaxes and moves up

  2. Internal intercostal muscles allow the ribs to return to its resting position

  3. Chest cavity decreases and so the air pressure inside lungs increases, hence it's forced out
• External respiration


  • De-oxygenated (no oxygen) blood travels in the capillaries to the alveoli, where carbon-dioxide diffuses out of the blood and into the alveoli
  • Oxygen that has been brought into the alveoli through inspiration diffuses across the alveoli membrane and into the capillaries
  • Oxygenated blood being taken away from the lungs, back to the heart where it gets pumped around the body for use, while the carbon-dioxide is expired into the atmosphere

  
• Internal respiration


  • The internal exchange of gases occur between the capillaries that encase cells, for us particularly muscle cells, and the cell itself
  • Oxygenated blood is brought to the muscle, where oxygen is taken out of the blood and transferred to the muscle tissue, while at the same time carbon-dioxide is taken out of the muscle cell and brought into the blood
  • Oxygen is transported through the blood attached to haemoglobin, and travels in the muscle attached to myoglobin
  • The exchange of gases across the membranes of the capillary and the muscle is referred to as diffusion and is known as internal respiration
  • The carbon-dioxide is then taken to the lungs via the heart in order to remove the carbon-dioxide and receive oxygen again (external respiration)

  
• Gaseous exchange


  The exchange of gases between the body and the environment