The Complete process of
respiration Can be explained under following headings:
* Breathing or pulmonary
ventilation
* Exchange of gases in alveolie
* Transport of oxygen
* Exchange of gases in Cells (at
Cellular level)
* Transport of Carbon dioxide
* Release of Carbon dioxide in alveolie.
⇒ Intercoastal muscles: are muscles lying in between Ribs. 11 pairs of Intercoastal muscles are present in between 12 Pairs of Ribs and are of two types ; External intercoastal or Inspiratory muscles and Internal intercoastal or expiratory muscles.
when EICM contracts the IICM
relaxes and Ribs move upward and outward which increases size of thoracic
Cavity and inspiration occurs.
When IICM Contracts the EICM
relaxes and ribs move downward and inward which decreases size of thoracic
Cavity and expiration occurs.
*Breathing
or pulmonary ventilation: is the
process of intake of atmospheric air up to lungs and through out of air from lungs
to atmosphere. It Consists of inspiration and expiration.
⇒ Inspiration: It is the process
by which atmospheric air reaches up to lungs. During it;
-
Inspiratory muscles or EICM Contracts while IICM relaxes
- Ribs
move upward and outward.
-
Diaphragm Contracts
- size of
thoracic Cavity increases and size of lungs also increases
-
Air
pressure inside lungs decreases and atmospheric air Comes into lungs through
respiratory tract.
This
Completes inspiration.
⇒ Expiration: It is the process by which air in
lungs Passes out to atmosphere. During it;
-
Expiratory muscles or IICM Contracts while EICM relaxes
- Ribs
move downward and inward
-
Diaphragm relaxes & become dome Shaped
- size of
thoracic Cavity decreases and size of lungs also decreases.
- Air
pressure inside lungs increases and air in lungs passes out to atmosphere
through respiratory tract.
This
Completes expiration.
* Exchange of gases in alveolie: In alveolie exchange of gases takes
place by the process of diffusion. The inspired air ultimately reaches into
alveolie of lungs and exchange of gases takes place between the air in alveolie
and the blood in the Capillaries around the alveolie. During this exchange the oxygen of the
inspired air passes into blood and Carbondioxide in blood is released into
alveolie. these respiratory gases move freely by diffusion which takes place
from higher concentration to lower Concentration. The process of diffusion is
directly proportional to the partial pressure of gas and solubility of the gas.
During diffusion gas has to pass through respiratory membrane.
The Partial pressure of oxygen ( PO2 ) in alveolie is higher (100mm Hg) than that in the deoxygenated blood in the Capillaries of pulmonary artery(40mm Hg). Thus, the movement of oxygen is from alveolie to blood.
The partial pressure of Carbondioxide (PCO2) is higher in deoxygenated blood
in the Capillaries of pulmonary artery (46mm Hg) than in alveolie (40mm Hg).
Thus, the movement of Carbondioxide is from blood to the alveolie.
* Transport of oxygen: The oxygen is transported from alveolie up to
cellular level in two ways :
⇒
As dissolve oxygen: About (1-3)% O2 is transported as dissolved oxygen.
the oxygen dissolves in water of plasma.
⇒
As oxyhaemoglobin: About (97-99)% O2 is transported as oxyhaemoglobin
(Hb.02). The oxygen combines with haemoglobin (Hb) to form oxyhaemoglobin.
Haemoglobin:
Hb is iron containing pigment in RBC and is Called respiratory pigment.
Hb Contains globin (protein) and heme group (iron) part.
⇒
The globin part is 95% part and Consists of four polypeptide Chains ; two alpha
chains and two beta chains. These polypeptide Chain ( Chains of aminoacids
linked by peptide bond ) are linked by disulphide bond.
⇒
The heme group is 5% part and Consists of Four heme group
each attached with each polypeptide Chain. Each heme group Consists of
tetrapyrrole ring (or porphyrine ring) with Fe++ (Ferrous iron) at Centre.
Each iron can get attached with one molecule of oxygen. Thus, Each Hb Can
Carry up to 4 molecules of Oxygen.
⇒ In adult, about (12-16) gm Hb is present in 100 ml of blood. Each gm Hb Carries about 1.34 ml of oxygen. Thus, About 20 ml oxygen is carried by 100 ml of blood.
*Exchange of gases at Cells: The oxygenated blood is carried from the blood capillaries of alveolie to heart by pulmonary veins and heart distributes this oxygenated blood to Various body parts through arteries. these arteries divides to form arterioles Which further divide to form Capillaries. the exchange of oxygen and Carbondioxide between tissue blood Capillaries and tissue Cells take place by diffusion and is Called internal respiration.
when oxyhaemoglobin reaches at tissue
level, the oxyhaemoglobin dissociates to release oxygen. The rate of
dissociation depends upon nature of the Cell. If the Cell is metabolically
active , the rate of dissociation become high. In metabolically active Cell,
PCO2 is high while PO2 is low and temperature of the Cell is also higher.
The partial pressure of oxygen is higher (95 mm Hg) in blood capillaries than
that of body cells(40 mm Hg) and the Partial pressure of Carbon dioxide is
lesser ( 40mm Hg) in blood Capillaries than that of body cells (46 mm Hg).
Therefore, oxygen diffuses from Capillary blood to cells through tissue fluids
and Carbondioxide diffuses from the body Cells to the Capillary blood via
tissue fluid. Now, the blood become deoxygenated.
* Transport of Carbon dioxide: Carbon dioxide is transported from
tissues to lungs by blood. Both plasma and haemoglobin transports Carbon
dioxide. In 100 ml of arterial blood about 48ml CO2 is present while in venous
blood 52ml CO2 is present. Thus, 100ml blood receives about 4mI of Carbon
dioxide from tissue and gives to alveolie. The Carbondioxide is transported In
three ways:
⇒
As Carbonic acid: About 7% Carbon dioxide is transported as Carbonic
acid which is formed by dissolution of
C02 in Water. Each 100 ml of blood transfers about 0.28ml of C02 in
dissolved form.
⇒
As carbaminohaemoglobin: About 23% Carbon dioxide ( About 0.92ml CO2 is
transferred by 100ml of blood as
carbaminohaemoglobin) is transported as Carbaminohaemoglobin which is formed by
reversible Combination of Carbondioxide with amino group of globin part of
haemoglobin.
Hb. NH2 + CO2 → Hb.NHCOOH
⇒
As bicarbonates of sodium and potassium: About 70% Carbon dioxide( about
2.8ml) is transported as bicarbonates of Sodium and potassium. The CO2 enters
inside RBC where it Combines with Water to form Carbonic acid in presence of
enzyme Carbonic anhydrase which acts as Catalyst. In presence of Same enzyme
Carbonic anhydrase, the Carbonic acid dissociates to form hydrogen ion and
bicarbonate ion. most of the bicarbonate ions diffuses into plasma. TO maintain
electroneutrality , equal amount of Chloride ions diffuses into RBC from
plasma. This exchange of bicarbonate ions of RBC and Chloride ions of plasma is
Called Chloride shift or Hamberger effect.
The bicarbonate ions in plasma combines with sodium and potassium ions in
plasma to form bicarbonates of sodium and potassium.
* Release of Carbon dioxide in alveolie: when Compounds with Carbon
dioxide like Carbonic acid, Carbamino compound of haemoglobin and bicarbonates
of sodium and potassium reaches at alveolie where PO2 is high these Compounds
dissociates to release CO2.
H2CO3 → H20 + CO2
Hb.NHCOOH → Hb.NH2 + CO2
2NaHC03 → Na2C03 + H20 + 2CO2
2KHCO3→ K2C03 + H20 + 2CO2
* percentage saturation of Hb: The amount of 02 Carried by Hb at a
particular time is called percentage Saturation of blood. It depends upon pO2,
PCO2, PH, temperature and
2,3 BPG ( 2,3 Biphosphoglycerate).
* oxygen dissociation curve: when
a graph is plotted between PO2 and percentage saturation of blood a
curve is obtained Called Oxygen dissociation curve. It is sigmoid.
* Factors affecting oxygen dissociation curve: po2 , pco2, pH , H+ ions , temperature and 2,3 BPG( Biphosphoglycerate) affect oxygen dissociation curve.
The oxygen dissociation curve get shifted towards right when PO2 decreases, PCO2 increases, pH decreases or H+ ions increases, temperature Increases and 2,3 BPG increases while get Shifted towards left when po2 increases , PCO2 decreases, PH increases or H+ ions decreases, temperature decreases and 2,3 BPG decreases.
* Haldane effect: When Po2
increases and PH increases the C02 carrying Capacity of blood decreases. It
occurs at alveolie to release CO2. Due to it, the oxygen dissociation Curve get
shifted towards left.
• P50
value of Hb: It is the value of PO2 at which Hb is 50% saturated. It is
27mmHg. At this 100ml blood carries 10ml of blood.
• Myoglobin
is pigment (protein) present in skeletal muscles. It combines with one molecule
of O2. Its P50 value is 3mmHg.it means myoglobin has high affinity with oxygen
and combines with oxygen even Po2 is very low. It is store house of O2 in
muscles. Its dissociation curve is hyperbolic.
• CO
poisoning: Hb has 250 times more affinity with Carbon monoxide than that
with O2. Thus, CO combines with Hb to form carboxyhaemoglobin and blocks Hb
from carrying O2 effectively to cells. High level of CO causes headache,
dizziness and may leads to death.
• Rate
of respiration: No. of respiratory cycles in a minute is called
respiratory cycle. Each respiratory cycle consists of one inspiration and one
expiration. So, it is number of inspiration or expiration in a minute. It is
12-16 times per minute.
• Respiratory
quotient(RQ): The ratio of amount of CO2 produced with amount of O2 consumed is called Respiratory quotient.
It is 1 for Carbohydrate, 0.8 for protein and 0.7 for fat. For anaerobic
respiration it is 0 as no O2 is consumed.