BLOOD
BLOOD
The circulatory system is made up of the heart, blood and blood vessels. Blood is the fluid that flows in the circulatory system and carries substances around the body.
BLOOD COMPONENTS:
Blood is made of a liquid called plasma and blood cells that float in plasma. If the test tube of blood is left to stand for a while, the blood cells will sink to the bottom of the test tube and separate from the plasma which is a clear yellow liquid. There are 55% of plasma and 45% of blood cells in your blood. Blood plasma carries three types of blood cells: red blood sells, white blood cells and platelets. They have different shapes and carry out different functions. When blood reaches the lungs, gas exchange occurs when carbon dioxide is diffused out of the blood and oxygen is diffused from the alveoli into the blood. This oxygenated blood is pumped to the left hand side of the heart in the pulmonary vein and enters the left atrium. From here it passes through the mitral valve, through the ventricle and it is pumped all around the body by the heart. Blood contains antibodies, nutrients, oxygen and much more to help the body work. |
PLASMA
Plasma is the blood fluid that surrounds blood cells and carries them along as it flows through the blood vessels. Plasma is the mostly water and contains other substances that are dissolved in it. Useful substances dissolved in plasma are digested food and it will be transported to where it is needed in the body. Waste substances dissolved in plasma are carbon dioxide and urea.
WHITE BLOOD CELLS
White blood cells are the largest type of blood cell. They have a large nucleus and can change their shape. White blood cells protect the body from disease by fighting invading microbes that can cause infection. Some white blood cells fight against infection by surrounding invading microbes and then digesting them. Other white blood cells produce antibodies or antitoxins to fight against infection .
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RED BLOOD CELLS
Red blood cells are the most common type of blood cell. Red blood cells transport oxygen from the lungs to the body's cells, where is used in respiration. It contains Haemoglobin (which is a special pigment that combines with oxygen). It has disc-shaped, with a dent on each side to create a large surface area for gas exchange. There is no nuclear in the red blood cells, therefore, there will be more space for Haemoglobin and so more oxygen.
PLATELETS
Platelets are cell fragments that have broken off from other larger cells. They are much smaller than red and white blood cells and do not have a nucleus. Platelets help to make tiny fibres that form a net at the site of a cut. Therefore, red blood cells are trapped in this net forming a blood clot to prevent blood keep bleeding. The clot dries and forms a scab which protects the cut while new skin grows.
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