Английский язык для медиков - Страница 8

Monocytes possess an eccentric nucleus. The cytoplasm has a ground—glass appearance and fine azurophilic granules.

Monocytes are the precursors for members of the mo—nonuclear phagocyte system, including tissue macropha—ges (histiocytes), osteoclasts, alveolar macrophages, and Kupffer cells of the liver.

New words

mesodermal – мезодермальный

erythrocytes – эритроциты

leukocytes – лейкоциты

fibrous proteins – волокнистые белки

immune – иммунный

humoral – гуморальный

to contain – содержать

nuclei – ядра

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 fibrino—gen, 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 intravascular 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 en—dothelial cells, which begin as blind—ended tubules or sac—cules 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

aqueous – водный

solution – раствор

proteins – белки

inorganic – неорганический

salts – соли

organic – органический

albumin – альбумин

globulins – глобулины

alpha – альфа

beta – бета

gamma – гамма

fibrinogen – фибриноген

lymphatic – лимфатический

vessel – сосуд

endothelium – эндотелий

circulation – кровообращение

lymph – лимфа

ubiquitous – вездесущий

notable – известный

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, agranulocytes, and platelets. Red marrow is characterized by active hemato—poiesis; 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 chro—matin, 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 chroma—tin which appears in a «checkerboard» pattern. The po—lychnsia of the cytoplasm is due to the increased quantity of acidophilic hemoglobin combined with the basophilia of cytoplasmic polyribosomes.

Normoblast (orthochromatophilic erythroblast) is a cell with a small heterochromatic nucleus that comprises ap proximately 25 % of its mass. It contains acidophilic cytoplasm because the large amount of hemoglobin and degenerating organelles. The pyknotic nucleus, which is no longer capable of division, is extruded from the cell.

Reticulocyte (polychromatophilic erythrocyte) is an immature acidophilic denucleated RBC, which still contains some ribosomes and mitochondria involved in the synthesis of a small quantity of hemoglobin. Approximately 1 % of the circulating RBCs are reticulocytes.

Erythrocyte is the mature acidophilic and denucleated RBC. Erythrocytes remain in the circulation approximately 120 days and are then recycled by the spleen, liver, and bone marrow.

New words

reticular – сетчатый

sinusoids – синусоиды

granulocytes – гранулоциты

agranulocytes – агранулоциты

active – активный

yellow – желтый

glycoprotein – гликопротеин

erythropoietin – эритропоэтин

amount – количество

hemoglobin – гемоглобин

degenerating – дегенерирующие

condensed – сжатый

Granulopoiesis, thrombopoiesis

Granulopoiesis is the process of granulocyte formation. Bone marrow stem cells differentiate into all three types of granulocytes.

Myeloblast is a cell that has a large spherical nucleus containing delicate euchromatin and several nucleoli. It has a basophilic cytoplasm and no granules. Myeloblasts divide differentiate to form smaller promyelocytes.

Promyelocyte is a cell that contains a large spherical indented nucleus with coarse condensed chromatin. The cytoplasm is basophilic and contains peripheral azurophi—lic granules.

Myelocyte is the last cell in this series capable of division. The nucleus becomes increasingly heterochromatic with subsequent divisions. Specific granules arise from the Golgi apparatus, resulting in neutrophilic, eosinophilic, and basophilic myelocytes.

Metamyelocyte is a cell whose indented nucleus exhibits lobe formation that is characteristic of the neutrophil, eos—inophil, or basophil. The cytoplasm contains azurophilic granules and increasing numbers of specific granules. This cell does not divide. Granulocytes are the definitive cells that enter the blood. Neutrophilic granulocytes exhibit an intermediate stage called the band neutrophil. This is the first cell of this series to appear in the peripheral blood.