Download 70- 732341 Phases of Respiration Respiration involves

Phases of Respiration
Respiration involves two respiratory phases: Inhalation and Exhalation.
1- Inhalation: is the phase by which air enters into the organism.
2- Exhalation: is the phase by which air leaves the organism.
Inhalation
State of lungs
Inflated
Position of the thoracic cage
Raised
Volume of the thoracic cage
Increase
Path of air
From outside to inside
State of diaphragm
Contracted (lowered)
Exhalation
Deflated
Lowered
Decrease
From inside to outside
Relaxed (raised)
Respiratory Tract – Air Pathway
Note:
Bronchus (Plural: Bronchi)
Alveolus (Plural: Alveoli)
*The right lung is larger than the left lung in size. The right lung is made up of 3 lobes (parts), while the left
one is made up of 2 lobes only.
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Exchange of gases
Diffusion of gases takes place; such that a gas diffuses from a medium of high pressure to a medium of low
pressure.
The exchange of gases takes place at the level of two sites in the body:
A) Exchange between alveolar air in the alveolus and blood:
-
Inhaled air (alveolar air) is rich with O2 and the blood entering the lungs is poor in O2 gas:
 so diffusion of oxygen takes place from alveolar air to blood
-
Inhaled air (alveolar air) is poor with CO2 and the blood entering the lungs is rich in CO2 gas:
 so diffusion of carbon dioxide gas takes place from blood to alveolar air
-
As a result: the exhaled air will be rich in CO2 gas and the blood leaving the lungs will be enriched by
oxygen.
Characteristics that favors this exchange include:
Great number of alveoli  Large surface area
Richness in blood capillaries (richly vascularized)
Thin wall
Direct contact with blood capillaries
1.
2.
3.
4.
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B) Exchange between tissues(group of cells) and blood:
Note: the exchange of gases between blood and tissue is done across the lymph.
-
Characteristics that favors the exchange between blood and tissues:
1. Rich in blood vessels
2. Slow speed of blood inside the blood capillaries
3. Thin wall of cells and blood vessels
4. Presence of lymph (fluid)
Transport of Respiratory Gases
20-30% by hemoglobin
98.5% by hemoglobin
Carbon
dioxide
gas
Oxygen
gas
60-70% in the form of
bicarbonate
1.5% dissolved in plasma
7-10% dissolved in
plasma
Hemoglobin + oxygen gas
Hb
+ O2
Oxyhemoglobin
HbO2
Hemoglobin + Carbon dioxide
Hb
CO2
Carbohemoglobin
HbCO2
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Hemoglobin and Color of Blood
Air pollution and nicotine addiction lead to the entry of many harmful substances into the body such as
carbon monoxide (CO). This gas combines with hemoglobin in an irreversible manner, leading to reduce the
amount of free Hb to carry respiratory gases. This can cause respiratory problems that maybe deadly in
severe case.
Hb + CO
HbCO
Some Respiratory Disorders
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