Notes For Class 11 Biology Chapter 17 Breathing And Exchange Of Gases Download In Pdf
Breathing : (External respiration) The process of exchange of O from the atmosphere with CO 2  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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