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Composition and functions of blood
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Blood
Blood is a kind of liquid connective tissue. It consists of intercellular substance – plasma, and blood cells.
Blood has following functions:
respiratory (supplies oxygen to body cells) nourishing
excretory (mainly harmful metabolism products – carbon dioxide and nitrogen)
immunological and thermoinsulating.
Blood cells are produced in red bone marrow (that is between bone trabeculi of spongy bone tissue).
Plasma - chemical composition:
90% water
9% organic compounds (immunological proteins, fibrinogen proteins, hormones, glucose, urea, amino acids)
1% mineral substances (e.g. sodium chloride, calcium and potassium ions)
Division of blood cells:
Erythrocytes (red blood cells)
they are the smallest, but the number of them is the biggest (about 5 million in 1 cubic millimetre)
they cannot move themselves, so they are transported with the blood current
they have no nuclei
they live for a very short period of time – about 100-120 days
they die eaten by spleen that resolves haemoglobin, contained in them.
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