Английский язык для медиков: конспект лекций - Беликова Елена - Страница 14

В cells differentiate in bone marrow and possibly in the gut-associated lymphatic tissues (GALT). They are the principal mediators of humoral immunity through their production of antibodies. Once activated by contact with an antigen, they differentiate into plasma cells, which synthesize antibodies that are secreted into the blood, intercellular fluid, and lymph. В lymphocytes also give rise to memory cells, which differentiate into plas ma cells only after the second exposure to the antigen. They are responsible for the secondary, or amnestic response that occurs when the body is exposed to an antigen for a second time. Monocytes vary in diameter from 15-18 mm and are the largest of the peripheral blood cells. They constitute 3-7% of leukocytes.

Monocytes possess an eccentric U-shaped or kidney-shaped nucleus. The cytoplasm has a ground-glass appearance and fine azurophi-lic granules.

Their nuclei stain lighter than lymphocyte nuclei because of their loosely arranged chromatin.

Monocytes are the precursors for members of the mononuclear phagocyte system, including tissue macrophages (histiocytes), osteoclasts, alveolar macrophages, and Kupffer cells of the liver.

Platelets (thromboplastids) are 2-3 mm in diameter.

They are a nuclear, membrane-bound cellular fragments derived by cytoplasmic fragmentation of giant cells, called megakaryocytes, in the bone marrow.

They have a short life span of approximately 10 days.

There are normally 150 000-400 000 platelets per mm³ of blood. Ultrastructurally, platelets contain two portions: a peripheral, light-staining hyalomere that sends out fine cytoplasmic processes, and a central, dark-staining granulomere that con tains mitochondria, va-cuoles, glycogen granules, and granules. Platelets seal minute breaks in blood vessels and maintain endothelial integrity by adhering to the damaged vessel in a process known as platelet aggregation. Platelets are able to form a plug at the rupture site of a vessel because their mem brane permits them to agglutinate and adhere to surfaces.

Platelets aggregate to set up the cascade of enzymatic reac tions that convert fibrinogen into the fibrin fibers that make up the clot.

New words

blood – кровь

to be considered – рассматриваться

modified – измененный

mesodermal – мезодермальный

erythrocytes – эритроциты

leukocytes – лейкоциты

platelets – тромбоциты

fibrous proteins – волокнистые белки

cellular – клеточный

elements – элементы

immune – иммунный

humoral – гуморальный

important – важный

trans porting – транспортировка

carbon – углерод

dioxid – диоксид

to contain – содержать

circular – проспект

dark-stained – запятнанный

nuclei – ядра

scanty – скудный

precursors – предшественники

short – короткий

life – жизнь

span – промежуток

approximately – приблизительно

peripheral – периферийный

light-staining – легкое окрашивание

to aggregate – настраивать

to set up – устанавливать

Вставьте артикль, где необходимо.

1. He has… small family.

2. He has… father and… mother.

3. He has no… brother, but he has… sister.

4. His sister is… pupil.

5. She is… good girl, and she had… many Russian books, but she has no… English hooks.

6. There is… writing-desk in… room… writing-desk is good.

7. There is… lamp on.writing desk.

8. My uncle has… large family. They are six in… family.

9. My father is… engineer.

10. He works at… big factory.

11. We have… good library.

12. Our books are in… big bookcase.

13. In your sister… married?

14. What do you do after… breakfast?

15. I go to… school.

16. When do you come… home?

17. I come… home at… half past two.

18. Do you like to watch TV in… evening?

19. There is… paper on… writ ing-desk.

20. My… books and… exercise-books arc on… writing-desk, too.

Вставьте артикль, где необходимо.

1. What… colour is your new… hat?

2. It is… white.

3. Is there… refrigerator in your… kitchen?

4. Where is… refrigerator in your… kitchen?

5. IT is in… corner of… kitchen.

6. There are… mirrow in our… living-room.

7. There are… flowers in… vase.

8. I have… tea in my… cup.

9. He has no… coffee in his… cup.

10. What… book did take from… library on… Tuesday?

11. I have books,… exercise-books and pens.

12. I work.an office.

13. Whose.those pen?

Answer the questions.

1. How is the blood considered?

2. What is the blood composed of?

3. What does blood carry?

4. Where does the blood carry oxygen and nutrients?

5. What does the blood contain in the immune system?

6. What do the formed elements of the blood include?

7. Hoe do we also call red blood cells?

8. What area do erythrocytes have?

9. What do eosinophils have?

10. What appearance does the cytoplasm have?

Make the sentences of your own using the new words (10 sentences).

Find the definite and indefinite articles in the text.

Plasma is the extracellular component of blood. It is an aqueous solution containing proteins, inorganic salts, and organic com pounds. Albumin is the major plasma protein that maintains the osmotic pressure of blood. Other plasma proteins include the globulins (alpha, beta, gamma) and fibrinogen, which is necessary for the formation of fibrin in the final step of blood coagulation. Plasma is in equilibrium with tissue interstitial fluid through capil lary walls; therefore, the composition of plasma may be used to judge the mean composition of the extracellular fluids. Large blood proteins remain in the intravascu-lar compartment and do not equilibrate with the interstitial fluid. Serum is a clear yellow fluid that is separated from the coagulum during the process of blood clot formation. It has the same com position as plasma, but lacks the clotting factors (especially fib rinogen).

Lymphatic vessels

Lymphatic vessels consist of a, fine network of thin-walled vessels that drain into progressively larger and progressively thicker-walled collecting trunks. These ultimately drain, via the thoracic duct and right lymphatic duct, into the left and right subclavian veins at their angles of junction with the internal jugular veins, respectively. The lymphatics serve as a one-way (i. e., toward the heart) drainage sys tem for the return of tissue fluid and other diffusible substances, including plasma proteins, which constantly escape from the blood through capillaries. They are also important in serving as a conduit for channeling lymphocytes and antibodies produced in lymph nodes into the blood circulation.

Lymphatic capillaries consist of vessels lined with endothelial cells, which begin as blind-ended tubules or saccules in most tis sues of the body. Endothelium is attenuated and usually lacks a continuous basal lamina. Lymphatic vessels of large diameter resemble veins in their struc ture but lack a clear-cut separation between layers. Valves are more numerous in lymphatic vessels. Smooth muscle cells in the media layer engage in rhythmic contraction, pumping lymph toward the venous system. Smooth muscle is well-developed in large lymphatic ducts.

Circulation of lymph is slower than that of blood, but it is nonetheless an essential process. It has been estimated that in a single day, 50% or more of the total circulating protein leaves the blood circulation at the capillary level and is recaptured by the lymphatics.