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Breathing : (External respiration) The process of exchange of O
from the atmosphere
with CO
2
[110]
2
produced by the cells.
Inspiration : Oxygen from fresh air taken by lungs and diffuses into the blood.
Expiration : CO
given up by venous blood in the lungs is sent out to exterior.
Respiration : The sum total of physical and chemical processes by which oxygen
2
and carbohydrates (main food nutrient) etc are assimilated into the system and the
oxidation products like carbon dioxide and water are given off.
Diaphragm : A muscular, membranous partition separating the thoracic cavity from
the abdominal cavity.
The pressure contributed by an individual gas in a mixture of gases. It is represented as
pO
for carbondioxide.
Pharynx : The tube or cavity which connects the mouth and nasal passages with
2
oesophagus. It has three parts
(i) Nasopharynx (anterior part)
(ii) Oropharynx (middle
part) and
(iii) Laryngopharynx (posterior part which continues to larynx)
Adam’s Apple : The projection formed by the thyroid cartilage and surrounds the
larynx at the front of the neck.
Tidal volume (TV) : volume of air during normal respiration (500 ml.)
Inspiratory Resrve colume (IRV) : Additional volume of air inspired by a forcible
inspiration. 2500 ml to 300 ml.
Expiratory Reserve Volume (ERV) : Additional volume of air, a person can expire
by a forcible volume (RV) volume of air remaining in the lungs even after a forciable
expiration (1100 mL to 1200 mL)
PURMONARY CAPACITES : Use in clinical diagnosis.
Inspiratory capacity (IC) = (TV + 1 RV)
Expiratory Capacity (E.C) = (T.V + ERV)
Functional Residual Capacity (FRC) = (ERV + RV)
Vital Capacity (VC ) = ( ERV + TV + IRV ) or the maximum volume of air a
person can breathe out after a forced inspiration.
Total Lung Capacity : It is cludes RV, ERV,TV and IRV or vital capacity + residual
volume.
Steps involved in respiration –
(i) Breathing or pulmonary respiration
(ii) Diffusion of gases (O
2
and CO
) across alveolar membrane.
(iii) Transport of gases by the blood
(iv) Diffusion of O
2
and CO
2
2
between blood and tissues.
(v) Utilisation of O
by the cells for catabolic reactions and resultant release of
CO
.
2
Inspiration : It the pressure with is the lungs (intro pulmonary pressure) is less than the at
maspheric pressure, ie there is negative pressure in the lungs with respect to the
atmospheric pressure.
♦ The contraction of diaphragm increases the volume of thoracic chamber in
antero-posterior axis.
♦ The contraction of external intercostal muscles lifts up the ribs and the sternum
causing an increase in the volume of thoracic chamber in the dorso ventral axis.
♦ It causes an increase in pulmonary volume decrease the intra-pulnonary
pressure to less than the atmospheric pressure.
♦ It forces the air out side to move in to the lungs, i.e, inspiration.
Expiration : Relexation of diaphragm and sternum to their normal positions and reduce the
thoracic and pulmonary volume.
It increases in intrapulmonary pressure slightly above the atmospheric pressure.
It causes the expulsion of air from the lungs, i.e, expiration.
Transport of CO
CO + HO
22
2
in the blood :- Carbonic anhydrase
about 20% of CO
2
H CO (Carbonic acid)
23
is transported by combining
with free amino group of Haemoglobin, in RBC.
HbNHCOOH (Carbamino haemoglobin)
Carbonic anhydrase
CO + HbNH
22
70% of CO
2
is transported as bicarbonates of sodium (NaHCO
) and
potassium (KHCO
)
3
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