February 26 Lecture - The Respiratory System The Exchange...

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February 26, 2009 The Respiratory System The Exchange of Gases - Occurs at the alveoli - Deoxygenated blood comes from the heart via the pulmonary artery to the alveolus - Blood will then become oxygenated and return to the heart via the pulmonary vein o Enters the heart on the left side to the left atrium o Transferred to the left ventricle and brought into systemic circulation - Inside of the alveolus has a moist surface o This allows oxygen to go into a solution to allow for the transfer of oxygen to reach the pulmonary vascularization - Networks of capillaries surround the alveolus o Pulmonary circulation and alveolus is separated by a double membrane layer - Blood in capillaries are moving in opposite directions depending on oxygenated content - Oxygen in the alveoli is contained by hemoglobin molecules in the blood - Once the oxygen molecules are taken up by the hemoglobin molecule they cannot dissociate (it is non-reversible) o This is because the oxygen molecules have a very high affinity for hemoglobin Component which attracts and binds oxygen molecule is iron It is through the Fe that the oxygen is held in the chemical embrace Oxyhemoglobin complex is formed - Amount of oxygen taken up by the blood is determined by activity (exertion) o Low exercise → ½ litres o High exercise → 5-6 litres - In order for the body to maintain homeostasis, oxygen must be extract to support processes and remove metabolic wastes such as carbon dioxide o Carbon dioxide must be picked up at the cellular level and transmitted back to the lung surface and released out of the blood stream o Once CO 2 is released at the alveolus it is released via the same tract that the O 2 entered - 97% of oxygen is extracted from alveolus by the hemoglobin molecule - RBC count is so important as they provide oxygen to metabolically active tissues o If cells are low, the ability to bring oxygen will be hindered - Some O 2 is absorbed by the plasma (3%) but major carrier is the RBC - CO 2 is released from the venous drainage of the tissue and carried as the carbonate form in the plasma (70%) about 23% in the hemoglobin and 7% is dissolved into the plasma o Plasma plays a larger role in the transport of CO 2 to the alveolus - CO 2 will then dissolve outwards at the alveolus and be released
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February 26 Lecture - The Respiratory System The Exchange...

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