1. Аудирование 20 мин

Тема – “A world guide to good manners. Japan.” (New Headway Intermediate, T.29, p. 130)

2. Аналитическое чтение. 40 мин

Выполните предтекстовые упражнения 1-3, 7-9 на стр 74-75 учебника Масловой А.М.

Прочтите текст The Heart and the Vascular System

Выучите лексический минимум из упр.7-8

3. Работа над грамматикой. 30 мин

Прочтите теоретический материал по теме Причастие на стр 296-297 и 301-302 грамматического справочника учебника Масловой А.М и выполните упр 3, 4 на стр 74 и упр 13, 15 на стр 76-77 учебника.

4. Краткое изложение содержания текста. 30 мин

BLOOD

In its liquid state blood contains a fluid called plasma plus microscopically visible cellular elements - 1) erythrocytes (red blood cells) of which 4,5 to 5 million are found in each cubic millimetre: the mature erythrocytes are non-nucleated red cells. 2) leucocytes (white blood cells) from 4,000 to 10,000 per cubic millimetre are of different types: leucocytes have nuclei. 3) thrombocytes (blood platelets) are much smaller fragments of protoplasm containing nuclear material. About 400,000 platelets occur per cubic millimetre.

The plasma which is mostly water, also has a very complex chemical nature. It contains dissolved gases - oxygen, carbon dioxide, and nitrogen. The proteins include albumin, globulin, and fibrinogen. The lipids include lecithin, fats and cholesterol. Carbohydrates are present as glucose, and blood also contains nitrogenous substances and inorganic salts. All these substances are found in varying quantities.

The plasma is the fluid portion of the blood before clotting has occurred. The serum is the fluid portion of the blood remaining after the coagulation process is complete.

Red blood cells, called also erythrocytes are filled with a solution of a red material known as haemoglobin. They contain no nucleus and have lost the power of reproducing themselves. After an active life of 120 days they are destroyed. Red cells, when placed in solution whose salt concentration is less than that of the haemoglobin, take up water, swell and burst.

DEVELOPMENT OF BLOOD CELLS

In health¹ the number of cells in the circulating blood remains very constant. The cells are continously being added to and removed from the blood stream but do not multiply there.

In the embryo, certain groups of mesodermal cells form blood islands. The outer cells of these groups flatten to form a lining for a small space, the inner cells float free in this space and multiply as primitive blood cells.

They are called megeloblasts. Megeloblasts - large nucleated cells - by successive divisions approximate in size to normal erythrocytes, develop haemoglobin in their protoplasm and finally lose their nuclei to form adult red corpuscles. The cites of these centres of red-cell formation (this process is called haemopoiesis) are widespread in the embryo and are found in liver and spleen and in the marrow cavities of bones where they form red bone marrow.

After birth the extent of haemopoietic tissues becomes less. In young children all the bones of the body are filled with red bone-marrow: with increasing age the extent of red marrow lessens and it gradually disappears from the limbs and is found only in the bones of the central skeleton; in the ribs, sternum, vertebrae, skull, clavicle, and pelvis in adults. In those bones from the age of 25 years onwards, it persists unchanged. The red marrow consists of a network of reticulin or stroma supporting many blood spaces or sinusoids (expanded capillaries). In these sinusoids, all kinds of immature red and white (granular) blood cells are found. The marrow, from which the blood-forming tissue has receded, consists of fatty tissue and is therefore yellow in colour. In certain diseases haemopoiesis is excessive and blood formation may revert to its embryonic sites: nest of developing blood cells will then be found in all bone marrow as well as in the spleen and liver.

Granular leucocytes are formed along with the red cells in the red bone marrow. There is a difference of opinion as to whether a very similar type of cell will produce a leucocyte series. Immature leucocytes are found along with immature forms of erythrocytes in the bone marrow.

Lymphocytes are found in large numbers in lymphoid tissues. Lymphoid tissues are found widely spread in the body and form the bulk of such organs as the spleen, tonsils and lymphatic glands. Structurally they consist of a framework of a loose fibres known as a reticulin network and formed by reticulin cells. The network is packed with lymphocytes. These are derived through intermediate cells from reticulin cells and groups of young lymphocytes are found in germinal centres that can be identified microscopically in many lymphoid tissues.

When blood is lost, for example by haemorrhage or by the action of certain poisonous substances the number of circulating corpuscles is reduced, and the blood forming tissues are called on to replace the losses. They do so by turning immature cells into the circulation, and the greater the need, the more primitive are the cells appearing in the blood stream.