Respiratory system human | Parts and 5 main Functions

Respiratory system human

☆ What is Respiratory system?

Respiratory system is  a catabolic  process (break down of food into  simple form)  and also biochemical process.It defined as ” Exchange of environmental oxygen into carbon dioxide take place between body and the outside complete environment.”

  • In other words we can say exchange of gases (viz. Oxygen and carbon dioxide) and oxidation of  food. is Respiratory system.


A process in which oxidation of organic compounds occurs in cell and energy is released is called as Respiration.”

Environmental Oxygen–>utilized by the organism———>to break down food ——–>Energy released ( by various activities in cells)———–>Carbon dioxide ( outer environment).

Hence,the process is  complete in the form of equation as :-

Food + Oxygen —> Carbon dioxide+ Water+ Energy

Respiratory system parts and functions☆☆

☆5 main functions of the respiratory system

  • Provide oxygen to tissue and excretion of carbon dioxide.
  • Excretionof volatile substance like ammonia.
  • Regulation of temperature through loss of heat in the expired air.
  • Maintanceof pH of blood .
  • Regulationof water balance through excretion of water vapour .
Respiratory system, Respiration
Working of Lungs in Respiratory system

    Two types of Respiratory system –

  1. Aerobic Respiration 

          (In presence of oxygen)

     Respiration involve use of molecular oxygen and release of carbon dioxide simultaneously. Such respiration is called aerobic respiration or aerobic metabolism.

  In other words{ breakdown of food in presence of oxygen called as aerobic respiration.}

Some important points are -:

  • This process is start in the Cytoplasm .
  • Continues in the mitochondria.
  • Each glucose molecule release 38ATP energy.
  • Water and carbon dioxide are produced as the waste products.
  • It occurs in plant and animal cells both.
  • It consists of 5 steps: glycolysis, pyruvate, oxidation,TCA cycle,ETS and chemosmotic ATP synthesis.
  • The release of energy in aerobic process is alot greater than in the anaerobic process.

Glucose + oxygen———–> carbon dioxide+ water+ large amount of energy

C6H12O6 + 6O2——->6CO2+ 6H2O+38ATP( 2830k) energy

  ☆ Aerobic respiration is of two main types

  • Direct Respiration

  It is the exchange of environmental oxygen with the carbon dioxide of the body cells without special respiratory organs and without the aid of blood. It is found in  aerobic bacteria, protists, plant, sponges, coelenterates, faltworms, roundworms and most arthropods.
  • Indirect Respiration
It involves special respiratory organs such as skin,buccopharyngeal lining,gills, lungs,and needs the help of blood.
 It  also involves the blood.

 ☆ Types of indirect respiration involving special respiratory organs are briefly described below –

i. Cutaneous Respiration-:

The exchange of respiratory gases through the vascular skin is called cutaneous respiration.It take place in annelids, cutaneous and amphibians.

  • It function in water as well as on land.

ii. Buccopharyngeal respiration:-

The exchange of respiratory gases through the thin , vascular lining of the baccopharyngeal cavity in certain amphibians such as frogs and toads is termed buccopharyngeal respiration.

  • It occurs in air.

iii. Branchial respiration-:

The exchange of respiratory gases in the gills is known as branchial respiration.

  •  It found in mammals, annelids, most crustaceans and molluscs,some insects larvae,echinoderms,all fishes and some amphibians.
  • It occurs in water only.

iv. Pulmonary respiration-:

  Some amphibians and land animals,namely reptiles,birds and mammals breathe atmospheric air with lungs .This exchange of gases through lungs is called pulmonary respiration

 2- Anaerobic respiration

        (In absence of oxygen)

Respiration may or may not produce carbon dioxide but does not utilize molecular oxygen.The process of releasing energy without the use of oxygen is called Anaerobic respiration or anaerobic metabolism.

 ☆ Some important points are-:

-: This process is only occur in cytoplasm.
-: In this process small amount of energy released.
-: It take place in human muscles and yeast, bacteria.
-: It produce only 2 ATP molecules
-: It is fast process as compare to aerobic respiration.
-: During this process each glucose molecule and carbon dioxide release.
-: It consists of 2 steps: glycolysis and incomplete breakdown of pyruvate.

☆ Difference between Anaerobic and Aerobic Respiration /Metabolism

Aerobic and Anaerobic Respiration
Aerobic and Anaerobic respiration

☆Other parts of Respiratory  system

Respiratory surface 

The surface at which exchange of gases (CO2 and O2) occurs is termed respiratory surface.

Respiratory medium

Most of the earth’s oxygen occurs in the air, but some is dissolved in water.Thus, air or water may serve as the source of oxygen for animals.The source of oxygen is called respiratory medium.

The respiratory medium supplies oxygen to the body at the body’s respiratory surface.

Respiratory substrates

    The substance respired are called Respiratory substrate. These are carbohydrates, proteins and fats.

  ☆ What is ATP

The word ATP stand for adenosine tri-phosphate.

  •  ATP was discovered by Lipmann.
  • Also known as   Energy currency of cell.
  • It is nucleotide that perform many essential roles in the cell .
  • The word ADP stand for adenosine di- phosphate.
  • Theenergy release during process of respiration is used to build up an ATP molecule from ADP and inorganic phosphate(pi).
                            ADP + pi ————–> ADP ~ pi = ATP
  • The energy equivalent to 30.5kj/mol is released.
  • Act is act as a mediator.
  • ATP also act as Coenzyme .
  •  ATP is also called energy currency of the cell .

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