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Transport in animals Typeit
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Multicellular organisms need transport systems to ensure that their needs are met. While mammals have a separate system for transporting oxygenated and deoxygenated blood, fish just have a circulatory system taking all blood from the heart to the gills to the body and back again. Fish and mammals both have a network of vessels to enclose the blood in the body, but insects have circulatory systems which move blood by peristalsis.
There are several types of blood vessels in mammals, all with different adaptations for their functions. For example, carry blood at high pressure, so they have thick layers of smooth muscle, collagen and elastic tissue to give them strength and allow them to withstand pressure.
The composition of tissue fluid is different from that of blood plasma. Tissue fluid is formed when plasma is forced from by the high pressure of the blood at the arterial end. The pressure of solutes in the tissue fluid also causes more water to be drawn into it.
The heart receives its own blood supply via the arteries. The cardiac cycle is under careful control and occurs in three phases. During , the atria contract at the same time, creating a small increase in pressure. Then, when the ventricles contract, the are pushed open by a greater increase in pressure in the ventricles, and all the muscles then relax during the diastole phase. Electrocardiograms can be used to monitor the electrical activity of the heart, and they produce a recognisable PQRST shape, where the QRS segment corresponds to the excitation of the . By comparing ECG traces to what is normal, a number of abnormal heart conditions can be identified - for example, if far fewer pulses occur than normal in a given time period, a patient might be diagnosed with .
Haemoglobin is a protein in red blood cells which can bind reversibly to oxygen, depending on the partial pressure of oxygen. Fetal haemoglobin has a higher for oxygen than adult haemoglobin, so its dissociation curve is shifted compared to the standard curve. When the concentration of carbon dioxide in the blood is high, the enzyme catalyses the reaction which forms carbonic acid, which can dissociate into hydrogencarbonate and hydrogen ions. To prevent the pH of the blood from dropping too low, haemoglobin acts as a buffer and associates with hydrogen ions to form .