ЛЕКЦИЯ № 16. Plasma

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.

Distribution of lymphatics is ubiquitous with some notable excep tions, including epithelium, cartilage, bone, central nervous sys tem, and thymus.

New words

plasma – плазма

extracellular – внеклеточный

component – компонент

aqueous – водный

solution – решение

proteins – белки

inorganic – неорганический

salts – соли

organic – органический

com pounds – составы

albumin – альбумин

to maintain – поддерживать

globulins – глобулины

alpha – альфа

beta – бета

gamma – гамма

fibrinogen – фибриноген

equilibrium – равновесие

lymphatic – лимфатический

vessel – сосуд

endothelium – эндотелий

attenuated – уменьшенный

circulation – обращение

lymph – лимфа

distribution – распределение

ubiquitous – вездесущий

notable – известный

Перед названиями наук, учебных предметов и языков артикль не употребляется.

E. g. He studies _ chemistry.

I speak _ English.

Заполните пропуски, где необходимо.

1. My friend's. flat is very comfortable.

2. There are… three rooms in… flat:… living-room,… study and. bedroom.

3… living-room is not very large.

4… walls in… living-room are blue.

5. There are. pictures on. walls.

6. There is… table in… middle of… room with some chairs around it.

7. To… left of… door there is… sofa.

8. Near… sofa there are… two large armchairs.

9. They are very. comfortable.

10. There is. piano in my friend's liv ing-room.

11… piano is to… right of.

12… doors of… bedrooms and… study are small.

13. When my grandfather was… young man, he studied… physics.

14. Do you speak… Spanish?

15. My uncle is… great specialist in… biology.

16. Japanese is more difficult than… French.

17. We listened to. very interesting lecture.

18. My father speaks… English and… French, but he does not speak… German.

19. We had… lesson of… mathematics yesterday.

20. We wrote. test in… mathematics.

Answer the questions.

1. What component of blood is plasma?

2. What components does the plasma have?

3. Where do large blood proteins remain?

4. Do large blood proteins equilibrate with the interstitial fluid?

5. What colour is serum?

6. Where is serum separated from?

7. What com position does the serum have?

8. What do lymphatic vessels consist of?

9. How do lymphatics serve?

10. How is developed the smooth muscle in large lymphatic ducts?

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

Find the definite and indefinite articles in the text.