Breathing : (External respiration) The process of exchange of O from the atmosphere with CO2 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 pO2 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 (O2 and CO2) across alveolar membrane.
(iii) Transport of gases by the blood
(iv) Diffusion of O2 and CO2 between blood and tissues.
(v) Utilisation of O by the cells for catabolic reactions and resultant release of CO2
MECHANISM OF BREATHING
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.
Respiratory Tract :
A pair of external nostrils nasal chamber through nasal passage→
nasopharynx→ glottis→ larynx→ trachea→ Left and right primary bronchi
→secondary and tertiary bronchi→ bronchioles→ vascularised bag like structures (alveoli) or air-sacs. Each lung is covered with double layered membrane known as pleura with pleural fluid between them.
Respiratory organs in animals :
(i) General body surface - Protozoans, annelids
(ii) Gills - Fishes, tadpole stage of frog and many other aquatic animals.
(iii) Air bladder - Bony fishes (Lung fishes)
(iv) Tracheae or Tracheal Tube - Insects and a few other arthropods.
(v) Lungs - All land vertebrates (amphibians, reptiles, aves and mammal)
Intercostal muscles : The muscles present between the sibs.
Physiology of Respiration :
(a) Exchange of gases - Diffusion of gases takes place from the region of
higher partial presure to lower (lesser) partial pressure)
(i) pO2 in alveolar air = 104 mm Hg.
pO2 in venous blood = 40 mm Hg.
O2 diffuses from alveoli to venous bllosd.
(ii) pCO2 is venous blood = 45 mm Hg.
pCO2 is alveolar air = 40 mm Hg
CO2 diffuses from venous blood to aveoli
(b) Transport of O2 by the blood - about 10%of CO2 forms caronic acid
with water of plasma.
(c) Transport of CO2 in the blood :-
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