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SPM Notes on Chapter Respiration

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This is a short notes on Respiration
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  STRUCTURE OF HUMAN LUNG 1.Respiratory system of man: - consists of trachea, lungs, bronchus, bronchiole and air sacs ( or alveolus ) - structure of trachea is supported by cartilage tissue ( ring  –  shaped , preventing it from collapse when there is a change in air pressure inside I - bronchioles end up at numerous tiny air sacs, the alveoli. Alveolus has a wet and thin / single layer of squamous epithelial cells through which gaseous exchange takes place. - alveolus is well provided with a network of blood capillaries. Oxygen diffuses out of alveolar air into blood capillaries, combines with haemoglobin in the red blood cells to form oxyhaemoglobin . Oxygen is transported to body tisues in the form of oxyhaemoglobin. 2.Both lungs ( and the heart ) are situated and enclosed in the thoracic cavity by ribs, intercostal muscles and the diaphragm. 3.The contraction of external and internal intercostal muscles bring about the inhalation and exhalation of air during breathing.  RESPIRATION During inhalation  : - External intercostal muscle contracts, internal intercostal muscle relaxes ( both are antagonistic muscles) results in the raising up of the ribs - Diaphragm also contracts cuausing it to move downward and becomes less curved - The capacity ( volume ) of thoracic cavity increases and the air pressure iside it is lower than in the atmosphere. - Air from outside is pushed into the lungs. -The revers process occures during exhalation. Haemoglobin molecule is made up of 2 alpha- and two beta- polypeptides. It is nearly spherical. The hydrophobic R-groups are pointing towards the centre and the hydriphilic ones are pointing outwards. Each heme group contains Fe +  ion. Each haemoglobin molecule can combine with 4 oxygen molecules to form oxyhaemoglobin.  OXYGEN DISSOCIATION CURVE The rate at which haemoglobin in saturated with oxygen depends on the partial pressure oxygen in the al veolar air, blood and insterstitial fluid in body tissue. Haemoglobin takes up more oxygen molecules and becomes saturated with oxygen faster in the region where partial pressure of oxygen is higher. Oxyhaemoglobin dissociates to release oxygen and haemoglobin when partial pressure of oxygen is low (and higher partial pressure of CO2 ) An increase in partial pressure of carbon dioxide will tend to reduce the the rate of oxyhaemoglobin formation, and hence the saturation of oxyhaemoglobin with oxygen. Therefore the dissociation curve of oxygen will move to the right as more carbon dioxide enters / added to the blood. This phenomenon is called the Bohr Effect  Oxygen Dissociation Curve and Transport of CO 2  in Blood 5% CO2 dissolves in blood plasma / part of it forms carbonic acid and carried to the lungs. 10  –  20% is carried as carbamino-haemoglobin in the red corpuscles. Carbon dioxide combines with the amino group at one end of the haemoglobin polypeptide to form carbaminohaemoglobin. HHbNH 2  + CO 2  HHbNHCOOH Haemoglobin Carbaminohaemoglobin In the cytoplasm of red blood cell, CO 2  is converted into H 2 CO 3 , catalysed by the enzyme carbonic anhydrase. H2CO3 dissociates into H+ and HCO3-. HCO3 diffuses out into blood plasma and carried to the lungs ( about 80%) Chloride shift     –  diffusion of Cl -  (chloride) ions into red blood cell to balance the elecktric charges in the cell. + Oxygen dissociation curves for adult and foetal haemoglobin. Oxygen dissociation curves for mioglobin and adult and foetal haemoglobin compared.
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