In other words at the particular pressure difference, the diffusion of carbon dioxide is 20 times faster than oxygen and that of oxygen is two times faster than nitrogen. It is further dependent on the solubility of the diffusing gases. The diffusing capacity is defined as the volume of gas that diffuses through the membrane per minute for a pressure difference of 1 mm Hg. The respiratory membrane has a limit of gaseous exchange between alveoli and pulmonary blood. 17.10) consists mainly of:Īll these layers form a membrane of 0.2 mm thickness. Due to this, the alveolar wall seems to be a sheet of flowing blood and is called respiratory membrane (= alveolar-capillary membrane). The wall of the alveoli is very thin and has rich network of blood capillaries. The exchange of gases (i.e., oxygen and carbon dioxide) between lung alveoli and pulmonary capillaries is called external respiration. (A) Exchange of gases between alveoli and blood (Fig. The respiratory quotient indicates the type of food oxidized in the body of the animal during respiration. Carbon dioxide is produced in most of the cases. In anaerobic respiration, there is no consumption of oxygen. For glucose, RQ (RQ 6CO 2/6O 2 – 1), for fats it is about 0.7, for proteins it is about 0.9 and for organic acids it is about 1.3 or 1.4. Respiratory quotient varies with different foods utilized in respiration. RQ = Volume of CO 2 evolved/Volume of O 2 absorbed Respiratory quotient is the ratio of the volume of carbon dioxide produced to the volume or oxygen consumed over a period of time in respiration. All pulmonary volumes and capacities are about 20 to 25 per cent less in women than in men and they are greater in tall persons and athletes than in small and asthenic (slight build) people.
It includes vital capacity and the residual volume (VC + RV). It is the total volume of air present in the lungs and the respiratory passage after a maximum inspiration. The vital capacity is higher in athletes, mountain dwellers than in plain dwellers, in men than women and in the young ones than in the old persons. depending upon age, sex and height of the individual. In fact total lung capacity minus residual volume is called vital capacity. This includes tidal volume, inspiratory reserve volume and expiratory reserve volume (TV + IRV + ERV). The maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration is called vital capacity. This includes residual volume and the expiratory reserve volume (RV + ERV). Volume of air that will remain in the lungs after a normal expiration is called functional residual capacity. This includes tidal volume and expiratory reserve volume (TV + ERV). It is the total volume of air a person can expire after a normal inspiration. It includes tidal volume and inspiratory reserve volume (TV + IRV). It is the total volume of air a person can inspire after a normal expiration. Respiratory or Pulmonary Capacities (Lung Capacities) : It is the volume of air which remains still in the lung after the most forceful expiration. It is the extra amount of air that can be expired forcibly after a normal expiration. It is the extra amount of air that can be inspired forcibly after a normal inspiration. This is about 500 mL, i.e., a healthy man can inspire or expire about 6000 to 8000 mL of air per minute. It is the volume of air inspired or expired during normal breath.
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