Respiration Topic in Biology


Let us study the topic of Respiration in Biology Together

What is Respiration?

“Respiration is the action of breathing.”

Definition of Respiration in Biology:

a process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances.

Respiration is of two types:

  1. Aerobic respiration
  2. Anaerobic Respiration

Properties Of Respiratory Surfaces:

The area where gaseous exchange takes place with the environment is called the respiratory surface. In case of humans  respiratory surface is Alveoli. And it takes place through Diffusion.

Human Respiratory System:

Human respiratory system consists of the following:

  1. Nose
  2. Nasal cavities
  3. Pharnx
  4. Larynx
  5. Trachea
  6. Bronchi
  7. Bronchioles
  8. Alveoli
  9. Lungs
  • Nose which is the externally visible part of the respiratory system.
  • Pharynx is cone shaped passageway leading from oral and nasal cavities.
  • Larynx is a complex structure that serves a dual function that is air canal to lungs and controller of its access.
  • Trachea, lies below the Larynx.
  • Trachea divides into two bronchi. And right bronchus has larger diameter and shorter than left bronchus.
  • Bronchioles are 1mm or less in diameter and consist of cuboidal epigthelium and a layer pf smooth muscle.
  • Alveoli forms the surface for gaseous exchange.
  • Humans have two lungs that is the left and the right lungs.

Lung Volumes and Capacities:

  1. Tidal volume
  2. Tidal capacity
  • Tidal volume is the air exchanged during one breath in and out in quiet breathing. Which is about 500ml.
  • Residual volume is the volume of air remaining in the lungs even after a forcible expiration.

The involuntary control of breathing is carried out by a breathing center which is located in the medulla oblongata.


  1. Inspiration
  2. Expiration
  • Inspiration is an active process. During inspiration the intercostal muscles between ribs contract. And the size of the thorax is increased. Therefore the lungs expand.
  • Expiration is a passive process. During expiration rib cage moves downward and inward. Reduction in size of thorax and diaphragm relaxes and becomes dome shaped.
  1. T ransport of oxxygen in blood
  2. Transport of carbon di oxide
  • As bicarbonate ions
  • As carboxyhaemoglobin
  • As dissolved CO2 in Plasma
  1. Haemoglobin (helps in transport of oxygen)
  2. Myoglobin(helps in storage of oxygen)


  1. Upper Respiratory Disorder
  2. Lower respiratoiry Disorder
Upper Respiratory Disorder:
  1. Sinusitis
  2. Otitis media
Lower Respiratory Disorder:
  1. Pneumonia
  2. Tuberculosis
  1. Emphysema
  2. Lung cancer

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