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Blood - moving around our bodies via the circulatory system, consisting of the arteries, veins and capillaries

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Introduction

Blood Blood constantly circulates throughout our body via the circulatory system, consisting of the arteries, veins and capillaries. The heart pumps this fluid to transport oxygen and nutrients to the body tissues and also removes wastes, in particular, carbon dioxide; a by-product of respiration. Blood consists of both red and white blood cells, as well as plasma. Each specific constituent of our blood serves a different purpose, all of which are vital for human survival. Red blood cells, also known as erythrocytes, make up the largest component of the blood, accounting for approximately 40% of blood volume. Without these specialised cells, the gaseous exchange involved in respiration would not be possible since red blood cells function to carry out the exchange of oxygen and carbon dioxide between the lungs and body tissues. However, for the red blood cells to successfully combine with oxygen, it is imperative that a normal amount of haemoglobin is present within the cell. The level of iron in the body determines the amount of this red protein pigment and consequently, if there is a deficiency of iron, less haemoglobin is produced, leading to anaemia and meagre oxygenation of the body's tissues. This can leave the sufferer feeling short of breath, fatigued and often very pale looking due to the diminished amount of the bright red haemoglobin. ...read more.

Middle

Because leukocytes are so vital for human existence, defects or problems with the white blood cells are often very serious. For example with Leukaemia, a cancer of the blood-forming tissues, the blood contains an abnormally abundant amount of white blood cells because of an uncontrolled proliferation that produces these atypical and immature leukocytes. The cells produced do not function properly and the overproduction suppresses the production of normal blood cells. Granulocytes account for approximately 70% of all white blood cells and are formed in the bone marrow. Neutrophils, eosinophils and basophils are all types of granulocytes and in their cytoplasm; all contain granules of varying consistencies. The main constituent of granulocytes is neutrophils, which are the first line of defence and can be distinguished by the fine granules in the cytoplasm and their lobed nucleus. This particular type of granulocyte is capable of ingesting and killing bacteria. Eosinophils and basophils both have coarse granules found in their cytoplasm and differ to neutrophils. Eosinophils act against infestations of parasitic larvae and are present in large numbers in covering or lining surfaces within the body. They are also involved in allergic responses. Basophils can release chemicals such as histamine and heparin and are also capable of ingesting foreign particles, as well as being involved to the inflammatory response to infection. ...read more.

Conclusion

When a wound begins to bleed, platelets congregate at the site to restrict the blood flow and begin coagulating the blood. The minerals that are transported in plasma and a protein called fibrinogen, help the sticky and irregularly shaped cells form a clot and when they are exposed to air, they begin to break apart. Fibrin is then produced because the platelets react with the fibrinogen and this leads to the fibrin threads forming a web-like mesh in which blood cells are trapped. Once this mesh of blood cells has hardened and dry, a scab is produced. Blood coagulation is extremely important, as without it we would bleed to death. Nevertheless, if blood clots in the wrong place, thrombosis may occur within a blood vessel of a diseased state. In an artery for example, a thrombus impedes the blood flow to the tissue it supplies and if the artery obstructed is one to the brain, this can cause a stroke since the brain cannot function normally without a steady supply of oxygen. Blood is not only the fluid of life by providing means for gaseous exchange but also the fluid of growth and protection because it transports nutrients from digestion and hormones throughout the body in addition to carrying bacteria fighting substances and wastes to the kidneys. Without blood, the human body would die and thus this rather incredible fluid is of uppermost importance to humans. Michelle Lockwood ...read more.

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