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Respiratory system is involved in exchange of respiratory gases and there by helps us to breathe. The human respiratory system consists of nostrils, nasal cavity, pharynx, larynx, trachea, bronchi and lungs. It helps in the movement of air in and out of the body. Exchange of O2 and CO2 occurs between air in the lung and blood. The entry of food into the wind pipe is prevented by a flap like structure called Epiglottis.
Lungs are the main respiratory organ. They are located within the chest cavity. The trachea, commonly called windpipe, is a tube supported by cartilaginous rings that connects the pharynx and larynx to the lungs, allowing the passage of air. The trachea divides into right and left bronchi and enter into the lungs. They divide further and ends in small air sacs called alveoli. The lungs are covered by a double layered pleura. Diffusion of gases (O2 and CO2) occurs across the alveolar membrane.
Exchange of gases by the respiratory system involves three different processes such as;
1. External Respiration: Intake of O2 from the air and releasing of CO2 from the lungs occurs through nostrils.
2. Internal Respiration: Taking in of oxygen and giving out CO2. The circulatory system transports O2 and CO2 to and from all parts of the body.
Hemoglobin in the red blood cells (RBCs) transport O2 and CO2.
3. Cellular Respiration: Cells take in O2 and release CO2
Aim: To prove that exhaled air is rich in carbon- di- oxide
Materials required: Two glass jars with lime water and a straw
Procedure: Leave the first jar with lime water undisturbed, blow air in to the second jar with the help of a straw
Observation: Lime water turns milky in few seconds in the second jar. The CO2 gas alone can change the lime water into milky white.
Conclusion: Carbon-di-oxide is present in the air that we exhale.
Each lung has about 300 million air sacs or alveoli.
Yawning helps us to take in more amount of O2 and to give out CO2
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