Carbon dioxide transport in respiration The CO2 produced during metabolism is a waste product and has been eliminated. The flow of CO2 is effected under a continuous pressure gradient. The transport of CO2 is effected in the following ways as physically dissolved CO2 and transport in chemical combination. 1. Physically dissolved CO2 Compared with O2, CO2 is 24 times […]

Transport of Oxygen in respiration Oxygen is transported in blood in two forms as physically dissolved O2 and O2 in combination with hemoglobin. 1. Physically dissolved O2 The O2 diffuses across the alveolar membrane and the lung capillary endothelium into the blood plasma where it is physically dissolved according to its solubility co-efficient and partial pressure. 0.003ml

Humoral Control of respiration Humoral control refers to those factors in the body fluids that influence ventilation like CO2, O2 and H+. The respiratory system functions to bring in O2 and eliminate CO2 from the body. This function is assisted by specialized receptors called chemoreceptors that monitor the levels of CO2, O2 and H+, and then send such information

Hering-breuer reflex The receptors for these reflexes are located in the lungs, particularly in the bronchi and bronchioles. The nerve impulses generated by these receptors are transmitted by fibers in the vagus nerves to the respiratory center. The effect of inflation-receptor stimulation is to inhibit further inspiration (stimulation of neurons in the dorsal respiratory group)

Neural Control of respiration Pulmonary ventilation is regulated closely to maintain the concentrations of H+, CO2, and O2 at relatively constant levels while meeting the needs of the body under varying conditions. If either the H+ or the CO2 concentration increases or if the O2 concentration decreases, their levels will be returned to normal by increasing ventilation. Conversely, if

Dead Space Ventilation The tidal volume is used to ventilate not only the alveoli, but also the airways leading to the alveoli. Because there is little or no diffusion of oxygen and carbon dioxide through the membranes of most of the airways, they com­pose part of dead space. The other part of dead space ventilation

Ventilation-perfusion relationships (V/Q) in animals For optimal gas transfer to occur in the lung, ventilation and perfusion must be matched. In man for the whole lung, alveolar ventilation and pulmonary blood flow are both about 5 L/min. Therefore, for the whole lung V/Q is about 0.8 – 1.2. Local airway responses and hypoxic pulmonary vasoconstriction

Physiology of gas exchange Alveolar gas exchange Usually, gas pressure is considered in terms of ­ total pressure, regardless of whether it is a single gas or a mixture of gases. However each gas in the mixture separately contributes to the total pressure. It is defined as the pres­sure exerted by a particular gas in

Pulmonary blood flow Dual circulation of the lung Bronchial circulation – arterial supply of tracheobronchial tree (as far as the terminal bronchioles), and other thoracic structures. About 2% of cardiac output. Pulmonary circulation – site of gas exchange between alveolar air and capillary blood. Mixed venous blood in pulmonary artery. Main pulmonary artery is much

Pulmonary passageway and pulmonary vascular resistance Respiratory passageway resistance Upper respiratory passageways – relatively large, very little resistance to airflow (unless obstruction such as from food lodging or cancer) Lower respiratory passageways – from medium-sized bronchioles on down, can alter diameter based on autonomic stimulation Parasympathetic – causes bronchoconstriction Sympathetic – inhibits bronchoconstriction Epinephrine – used to treat life-threatening bronchoconstriction