Respiration
Three stages of respiration.
1. Gas exchange between external environment and lungs
2. Gas exchange in alveoli
3. Cellular respiration
Demonstration of gas exchange using a model Figure
Materials required :- Small bell jar, gas tube, a cork bore, two rubber balloons, balloon membrane or polythene sheath,
several rubber bands
Method :- Set the apparatus as shown in the diagram. Push and release the balloon membrane and observe the
condition of balloons.
Observation : When rubber membrane is pulled down the
volume inside the bell jar increases. Then external gas enters
and balloons get inflated. When rubber sheath is released,
gas inside balloons go out as the volume of bell jar decreases.
Conclusion : Gas exchange between external environment
and lungs occurs due to changes of volume of lungs.
Human respiratory system
Main parts of the respiratory system,
Nasal cavity
Pharynx
Trachea
Larynx
Bronchi
Bronchioles
Alveoli
Q : Why nasal cavity is moist?
Due to the presence of mucus in the nasal cavity, the lining of it is moist.
Q : What is the function of mucus?
The bacteria, dust and other wastes found in inhaled air stick onto the mucus. This prevents the entry of them into the
lungs
Q : What is the function of cilia present on the lining of the nasal cavity?
By rhythemic movement of cilia the waste materials are sent out.
The materials that are collected at pharynx are removed out with saliva.
Q : What are the changes that take place when inhaled air passes through the nasal cavity?
Moisturizing/ Humidifying inhaled air
Warming up of inhaled air
Removal of wastes from inhaled air
Q : What happens during the inspiration?
Air enters into lungs.
For that, the volume of the lungs should increase.
To increase the volume of the lungs volume of the thoracic cavity should be increased.
Inter-costal muscles contract, therefore ribs move up and sternum moves forward.
At the same time the diaphragm contracts and reduce its curvature.
Due to above activities the volume of the thoracic cavity increases and with that volume of lungs increase.
So air enter into lungs through the nose.
Q : What happens during the expiration?
The volume of the thorasic cavity should decrease to reduce the volume of the lungs.
Inter-costal muscles relax.
So the sternum and ribs move into its original position.
The diaphragm relax and becomes curved.
Due to these activities the volume of the lungs decreases, thereby gas inside lungs move out through trachea
and then nasal cavity.
Q: Compare between inspiration and expiration
Inspiration Expiration
Air enters in to the lungs Gas is go out from the lungs
Volume of the lungs increased Volume of the lungs decreased
Volume of the thoracic cavity increased Volume of the thoracic cavity decreased
Inter costal muscles contract Inter costal muscles relax
Sternum and ribs move forward Sternum and ribs come to the original position
Diaphragm contract Diaphragm relax
Reduce curvature Increase curvature
The gas exchange that takes place in alveoli
The inhaled air reach into alveoli passing the nasal cavity, trachea , bronchi and bronchioles.
The alveoli is covered by a network of capillaries.
The O2 concentration inside the alveoli is greater than in the blood capillaries.
Therefore O2 diffuse out of the alveoli into capillaries.
Concentration of CO2 and water vapor is greater in the capillaries than inside the alveoli.
Therefore CO2 and water vapor diffuse into alveoli from blood capillaries.
The respiratory surface of the human is alveoli wall.
The gaseous exchange inside alveoli is taken place by diffusion.
Characteristics of a respiratory surface
The adaptations of the respiratory surfaces for efficient gas exchange.
1. Surface should be moistened and permeable for gas exchange
2. Surface should be thin for diffusion of gases
3. A larger surface area to exchange large volume of gas according to the needs of animals
4. Surface should be highly vascularized.
The respiratory surface of human is the wall of alveoli and the adaptations of the alveoli for efficient gas
exchange are as follows.
1. Presence of a blood capillary network around alveoli
2. Thin alveolar wall
3. Moist alveolar surface
4. Presence of large number of alveolar sacs
Cellular respiration
Respiration is the process of oxidation of simple foods within living cells.
Cellular Respiration is a chemical reaction.
This type of respiration is known as aerobic respiration.
Aerobic respiration and Anaerobic respiration
Aerobic respiration takes place inside cells in the presence of oxygen. It called Aerobic
respiration.
Respiration carried out by organisms without O 2 is known as anaerobic respiration.
