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How the respiratory system is adapted for the purposes of gas exchange

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Introduction

The purpose of this essay is to explain how the respiratory system is adapted for the purposes of gas exchange, including the processes by which the diffusion of gases occur and the factors that may affect this. Firstly, there will be an explanation of what respiration and gas exchange are. Then, the essay will look at the respiratory and cardiovascular systems and how they work together for gas exchange. Moving on, there will be an explanation on what happens to inhaled air as it is inspired and prepared for gas exchange in the body. Fick's law of diffusion will be explored, also pressure gradients and the solubility of gases will be described and the factors affecting these. All living cells need a source of energy in order to survive. All cells obtain energy through the process of respiration. Indge B. et al (2000) explains that "Respiration occurs in every cell within the body, generating adenosine triphosphate (ATP), using oxygen and producing carbon dioxide as a waste product" (pg. 73), see figure one. The organelle within cells that is responsible for respiration is the mitochondrion. Gas exchange is the movement of oxygen (O2) and carbon dioxide (CO2) in opposite directions across cell membranes. Gas exchange is achieved by diffusion. This is "the movement of particles (molecules or ions as the case may be) from a region where they are at a comparatively high concentration to a region where they are at a lower concentration" (Roberts M.B.V. ...read more.

Middle

CO2 also binds to haemoglobin, known as carbominohaemoglobin, and is transported back to the lungs to be expelled from the body. As CO2 is much more soluble in fluid than O2, it can also be transported within the blood plasma. The heart controls this transportation, using vessels called arteries and veins, which pump the blood to the lungs to collect O2 and dispose of CO2 and then the blood returns to the heart where it is pumped around the body, see figure seven. Fick's law, shown below, can calculate the rate of diffusion. Ficks Law Rate of diffusion = Surface are X difference in concentration Thickness of membrane (Indge B. et al 2000, pg. 77) For a fast rate of diffusion, the surface area and difference in concentration have to be as large as possible, also the thickness of membrane, i.e. distance to travel, has to be as small as possible. A large surface area for diffusion is obtained in humans by the alveoli in the lungs. The structure of alveoli enables them to have a large surface area in relation to volume ratio, see figure eight. A factor affecting gas exchange with regards to surface area is a condition called emphysema, which is caused by smoking, also from coughing (creating pressure) and a congenital deficiency of elastic tissue in the lungs. It is where "the walls between adjacent alveoli break down" (Waugh A. and Grant A. ...read more.

Conclusion

So much nitrogen is forced into the blood that it causes a narcotic effect called nitrogen narcosis. Nitrogen is more soluble in lipids than water, so it tends to affect lipid-rich tissues like the central nervous system, bone marrow and fat deposits. "The diver becomes dizzy, giddy, and appears to be intoxicated" (Marieb E. 1998, pg. 830), which causes potential danger to the life of the diver under water. Any further danger can be avoided by a gradual ascend to the surface, so that the nitrogen has time to driven out of the tissues once again without causing any problems. In conclusion to this essay, it is clear that both the respiratory and cardiovascular systems work together to create the best environment for gas exchange and the most efficient organs to do so. The air is conditioned throughout the respiratory system in preparation for contact with the lower respiratory tract. The body is also adapted for as fast a rate of diffusion as possible. A large surface area in relation to volume ratio is gained by the structure of the alveoli, the difference in concentration is maintained by the constant flow of blood through the capillaries transporting the gases to and from the alveoli, and the distances for the gases to diffuse across is at an absolute minimum, using single celled layers. It is also clear that the human body is adapted for efficient gas exchange at sea level. Differing altitudes have an effect on the partial pressures and solubility of gases and so this affects gas exchange. Word Count - 1633 ...read more.

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