Blood - argomento di esame

BLOOD

Definition and functions

Blood is a special type of connective tissue, the only liquid tissue in our body. Its main functions are:

• Transports oxygen from the lungs to all cells and vice versa;

• Transports molecules (for example carbohydrates, lipids, amino-acids) from the intestine to all the

body’s cells and, in particular, to the storage organs [= organi di accumulo] (for example liver or adipose

tissue);

• Removes metabolic waste from the tissues and transports them to the organs that allow their excretion;

• Diffuses the hormones produced by the endocrine glands;

• Assists in the maintenance of the body’s water balance;

• Contributes to the body’s defence mechanism against pathogens;

• Contributes to the distribution of the heat produced by cell metabolism which regulates the body’s

temperature;

Blood is divided into two parts: formed elements which include erythrocytes, leucocytes and platelets, and

plasma, the liquid portion in which the formed elements are suspended.

The haematocrit is defined as the percentage of formed elements in the total volume of a blood sample. It

can be measured on venous or capillary blood; the classic technique uses the venous sample.

Composition of blood: plasma

Plasma is the liquid part of the blood, 90% of which is water and 10% protein and other solutes, such as

+ + ++ 3- -

glucose, amino acids, urea, K , Na , Ca , HCO , Cl .

Blood contains the following proteins:

• →

Albumin is the major protein reserve in our body produced by the liver and it has many function, like

transports hormones and maintains osmotic pressure as a carrier.

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Alpha-globulin includes proteins which cluster through (che si raggruppano attraverso)

electrophoresis. Each protein has a special transport function, for example hormone, cholesterol and

fatty acid transport. Indeed, fatty acid and cholesterol cannot be transported through the blood freely

but require special proteins, such as HDL which function as carrier (che funzionano da trasportatori?).

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Beta globulin contains a low density lipoprotein (LDL) for the transport of fatty acids, cholesterol and

iron.

• →

Gamma globulin consisting of antibodies made by the immune system’s B cells. These protein are

able to bind pathogens with a high affinity and promote their elimination.

Composition of blood: formed elements

The formed elements of blood are:

• Red blood cells or erythrocytes: are the major component of blood, described as biconcave disks. Their

main function is to transport oxygen from the lungs to all the tissues with haemoglobin and, vice versa,

carbon dioxide to the lungs with carbonic anhydrase. Red blood cells