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Gas Exchange System

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Gas exchange in mammals takes place in the lungs which are internally located within the chest cavity. The lungs are sac-like organs which play one of the main roles in the respiratory system. To begin with, air is breathed in through the nose and mouth. This process of taking air into the system is called inspiration or inhalation. When mammals inhale, their external intercostal muscles contract and the diaphragm (arched set of muscles between thorax and abdomen) located beneath the lungs also contracts, and moves down. This causes the rib cage to expand and move up, resulting in an increase in the chest/ thoracic cavity volume and a decrease in its pressure. Hence, due to the difference in the external atmospheric air pressure and the internal…show more content…
When insects inspire, air is taken in through the spiracles which are paired openings/ pores located on the outside along the thorax and abdomen of the insect. These spiracles are lined with hairs which filter the air entering the system to prevent clogging of the airway and reduction of the surface area available for gas exchange. Spiracles also aid in minimising water loss by the hairs which trap humid air, and the valves which help to control opening and closing. As insects are terrestrial organisms which may be prone to desiccation, and therefore loss of water by evaporation, closing their spiracles can allow them to help conserve water and ensure that the gas exchange surface is kept moist (for respiratory gases to be dissolved and diffuse into the muscle fibres). However, closing the spiracles may also mean that oxygen rich airflow is limited and so gas exchange efficiency would decrease, consequently affecting the rate of cellular respiration and production of energy required to meet the metabolic demands of an insect. Air then travels from the spiracles into the internal tracheae/ tracheal tubes that are supported by chitin rings or bands (a strong, lightweight material) which help to reinforce and provide flexibility to its structure. This ensures that the tracheae are held open instead of being compressed when vigorous body movements are made and that the gas exchange surface is still sufficiently ventilated with oxygen necessary for supplying the large amounts of energy needed for such body movements, especially flight when trying to escape predation. As there are numerous tracheal tubes which further branch out into tiny tracheoles, the surface area to volume ratio is increased so that maximum oxygen absorption can occur. The tracheoles are tiny tubes which end with a fluid filled tip that the respiratory gases are soluble in to allow for the diffusion of oxygen from the highly oxygenated air
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