Chapter # 10:
Gaseous Exchange
·
Inspiration/Inhalation:
The process of taking fresh
air inside the lungs for gaseous exchange is called inspiration.
Mechanism: During
inspiration, the rib muscles and diaphragm both contract thus increasing the
area of thoracic cavity and thereby reducing the pressure on lungs. As a
result, the lungs expand and pressure within them decreases and air from
outside rushes into the lungs to equalize pressure on both sides.
·
Expiration/Exhalation:
The process of expelling
the impure air outside the lungs into the environment after gaseous exchange takes
place in the lungs is called expiration.
Mechanism: During
expiration, the rib muscles and diaphragm both relax thus decreasing the area
of thoracic cavity and thereby increasing the pressure on lungs. As a result,
the lungs contract and air is expelled out of them into the environment.
·
Bronchitis:
The inflammation of bronchi
or bronchioles resulting in excessive secretions of mucus into the tubes and
leading to the swelling of tubular walls and narrowing of the tubes is called
bronchitis.
Cause: It is caused by
viruses, bacteria or exposure to chemical irritants e.g. tobacco smoke.
·
Cellular Respiration:
The process in which C-H
bonds in food containing high potential energy are broken by oxidation
reduction reactions and the energy released is transformed into ATP for various
activities is called cellular respiration. It occurs inside the cell.
Aerobic Respiration: Oxygen
is required for the complete oxidation of food and is termed as aerobic
respiration.
·
Breathing vs Respiration:
Breathing is the process
through which animals take air in their bodies to get oxygen from it and then
give out air for getting rid of carbon dioxide. While, respiration is the
process in which both gaseous exchange (breathing) and cellular respiration
occurs i.e. C-H bonds are broken by oxidation reduction reactions and energy is
released and stored in the form of ATP. Carbon dioxide formed during the
process, moves out of the body.
Breathing is only a
mechanical process of exchange of gases while respiration involves both
mechanical (external respiration/gaseous exchange) and biochemical (cellular
respiration) processes.
·
Diaphragm:
The muscular sheet made up
of skeletal muscles which separates the thoracic cavity from the abdominal
cavity is called diaphragm.
Significance: It helps in
inspiration and expiration. In normal or relaxed position, it is dome shaped
thus reducing the area of thoracic cavity for expiration while when contracted,
it becomes horizontal thus increasing the area of thoracic cavity for
inspiration.
·
Symptoms of Emphysema:
The destruction of the
walls of alveoli resulting in larger sacs but with less area for gaseous
exchange is called emphysema. Following are the main symptoms:
Shortness of breath,
fatigue, recurrent respiratory infections and weight loss. (In Points)
·
Trachea and structure:
The 12 cm long tube through
which air passes, which continues from larynx and lies in front of the esophagus
is called trachea. It is also called windpipe.
Structure: There are
C-shaped cartilaginous rings in the wall of trachea which prevent its
collapsing. It is also lined with ciliated and glandular cells for the
filtration of air passing through it. On entering the chest cavity, the trachea
divides into two smaller tubes called bronchi.
·
Passive Smoking Injurious:
The inhalation of smoke
from another person’s smoking is called passive smoking. It can be injurious to
health as:
1- It is capable of causing
Lung Cancer.
2- The smoke from the
burning end of a cigarette is more dangerous than the smoke from the filter end.
3- Heart disease risk of
passive smokers increases by 25-30%.
4- Lung cancer risk
increases by 20-30%.
5- Many people are allergic
to cigarette smoke thus it causes asthma.
6- Passive smokers can also
develop other disorders like regular active smokers e.g. CO poisoning, Increase
in blood platelets, developing of lung infections etc.
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