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• Inhalation – process of taking oxygen rich air inside the body.
• Exhalation – process of throwing carbon dioxide rich air outside the body
• Breathing – inhalation and exhalation together contributes breathing
• Mechanism of breathing
  • During inhalation, the muscular sheet called diaphragm situated below lungs undergo contraction. Due to which the diaphragm moves downwards and becomes flat. It causes increase in the chest cavity. With this movement the pressure of air outside the body becomes larger than the pressure of air present in the lungs. To equalise the pressure air rushes into the lungs.
  • After absorption of oxygen from air into blood, and release of carbon dioxide from blood into the lungs; the exhalation begins.
  • Thus the diaphragm relaxes. It moves up and decrease the chest cavity. Due to which lungs get contracted. Due to which pressure of air inside the lungs becomes greater than the pressure of air outside the body. To equalise the pressure now, the excess air get rushed out of the body through nostrils. This is called exhalation.
• Breathing rate – breathing of a person in one minute is called breathing rate
• Need of respiration –
  • It is important for survival of living organisms.
  • Carbon dioxide is removed from the body through respiration
• Human respiratory system
  • Respiratory system of humans have different parts Nasal chamber, pharynx, larynx, trachea, bronchi, lungs, diaphragm.
  • Respiration starts through breathing.
  • Air inhaled contains oxygen which is transferred to blood stream.
  • Oxygen is delivered to all the cells which generates energy.
  • Carbon dioxide from the cells are taken back to the lungs and are thrown outside the body through nostril
• Modes of respiration –
  • Diffusion – Diffusion is a process in which molecules move from region of high concentration to region of low concentration through semipermeable membrane.
    • concentration of oxygen is higher outside the cell than inside, therefore oxygen gets diffused from outside to inside of the cell through plasma membrane
    • concentration of carbon dioxide is higher inside the cell than outside so it get diffused from cell body to outside through plasma membrane.
  • Some animals like frog and earthworm, breath from their skin, as skin is very thin, they are able to exchange gases.
  • Cockroach and similar organisms have spiracles on their body which are tiny holes connect to trachea. Through these exchange of gases takes place
  • Aquatic animals like fish breathe through gills.
• Respiration in plants
  • Plants take in oxygen rich air from the stomatal openings present under the leaves. From this particular place exchange of gases takes place in plants.
  • Lenticels, stomata, etc are some area of gaseous exchange
• Watch complete video on respiration of plants here.