Gas exchange is carried by simple diffusion.
Diffusion means flow of materials (gas, liquid or solid) from a region of higher concentration to low concentration as the oxygen flows from alveoli to blood capillaries, and carbon dioxide flowsfrom blood capillaries to inside alveoli.
Gas exchange in alveoli
Alveoli are well adapted for gas exchange by:
  • Large surface area
  • Highly surrounded by a network of blood capillaries for blood supply
  • Thin, single epithelial layer gives a short diffusion distance
  • Walls are made up of moist film, allowing gases to dissolve easily.
The exchange of gases is carried by the pigment called haemoglobin (Hb) in the RBC.
  • Haemoglobin plus oxygen converted as oxyhaemoglobin.
  • Haemoglobin plus carbon dioxide converted as carbaminohaemoglobin
Why we sneeze?
The air contains a wide range of dust particles such as smoke, dust and pollens. These particles usually get trapped in the hair found in our nasal cavity during inhalation. Sometimes these particles irritate the lining of the nasal cavity resulting in sneezing. Thus sneezing helps us to remove the dust particles that we inhaled by our nostrils.
During sneezing, everyone should always cover the nose with clean tissue or cloths so that others do not inhale the foreign particles which are expelled.
Right ways to sneeze safely
Smoking is a highly destructive behaviour that damages the lungs. Therefore, this must be stopped to live a healthy life.
Depicts the health issues of smoking
Smoking causes cancer to a healthy person, and in the below the comparison between the healthy and cancerous lung has shown.
Healthy lung vs Cancer lung