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.
ЛЕКЦИЯ № 17. Hematopoietic tissue
Hematopoietic tissue is composed of reticular fibers and cells, blood vessels, and sinusoids (thin-walled blood channels). Myeloid, or blood cell-forming tissue, is found in the bone marrow and provides the stem cells that develop into erythrocytes, granulocytes, agranulo-cytes, and platelets. Red marrow is characterized by active hematopo-iesis; yellow bone marrow is inactive and contains mostly fat cells. In the human adult, hematopoiesis takes place in the mar row of the flat bones of the skull, ribs and sternum, the vertebral column, the pelvis, and the proximal ends of some long bones. Erythropoiesis is the process of RBC formation. Bone marrow stem cells (colony-forming units, CFUs) differentiate into proerythroblasts under the influence of the glycoprotein erythropoietin, which is produced by the kidney.
Proerythroblast is a large basophilic cell containing a large spherical euchromatic nucleus with prominent nucleoli.
Basophilic erythroblast is a strongly basophilic cell with nucleus that comprises approximately 75% of its mass. Numerous cytoplasmic polyribosomes, condensed chromatin, no visible nucleoli, and continued hemoglobin synthesis characteristics of this cell.
Polychromatophilic erythroblast is the last cell in this line undergoes mitotic divisions. Its nucleus comprises approximately 50% of its mass and contains condensed chromatin which appears in a «checker-board» pattern. The polychnsia of the cytoplasm is due to the increased quantity of acidophilic hemoglobin combined with the basophilia of cytoplasmic polyribosomes.