After that read the text aloud, trying to imitate the intonation

a- granules contain a set of specific, as well as non-specific peptide mediators of coagulation and anticoagulation, inflammation, regeneration and immunity. Their membranes reveal an early platelet-leukocyte activator of aggregation (P-selectin) that appears on their surfaces during the activation of platelets. a- granules also contain thrombospondin (another aggregation activator), nWF, and VIII and V coagulation factors, 4th thrombocytic heparin-neutralizing factor, b-thrombomodulin, and, finally, fibrinogen and fibronectin.

d- granules (dense bodies) are rich in biogenous amines (histamine, serotonin and epinephrine), adenine nucleotides (ADP and ATP), ionised calcium.

So-called l- granules are lysosomes with typical enzymatic content including acid hydrolases.

Major functions of platelets are:

- forming of a white thrombus (also called primary, or agglutination, or the Zahn thrombus) which is responsible for primary hemostasis (hemostasis in the vessels of diameters less than 50 -100 mcm);

- triggering out a spasm in the injured blood vessels through lipid and amine vasoconstrictors;

- speeding up fibrin formation (activation of platelets results in decrease of sphyngomyelin content on their surface while its phosphatidylcholine content increases – formerly this phenomenon was called “blood thromboplastin” or “3^rd platelet factor”; this results, in its turn, in the development of phospholipide-glycoprotein cradle for fibrinogenesis and growth of the thrombus; in addition, platelets produce I, V, and VIII coagulation factors);

- initiation of tissue reparation and angiogenesis on account of the growth factors (chronic thrombocytopenias result in faulty reparation of blood vessels and development of secondary vasopathiae);

- stabilization of fibrin (XIII factor) and thrombus retraction;

- anti-hemostatic functions effected through storage and liberation of antithrombin III, S- and C- proteins;

- pro- and anti- inflammatory functions effected through a set of mediators.

Hemostasis in the vessels of diameters more than 50 -100 mcm takes place owing to the formation of a secondary (coagulation) thrombus. The thrombus of such kind consists of a head, a body and a tail. The head is the primary agglutination thrombus. For the coagulation thrombus to form, the presence of a great amount of stabilized fibrin polymer is necessary. This task is accomplished through the coagulation system (that is, fibrin-formation), which is activated in response to the appearance of the primary white thrombus with a negatively charged surface, or the activation of the system may be initiated by the contact of the system’s proteins with polyanion molecules, or as a result of contact of f. XII with a rough surface of basal membrane revealed after endothelium damage.

3Do the following statements agree with the information given in the reading passage?

Write

TRUE if the statement agrees with the information

FALSE if the statement contradicts the information

NOT GIVEN if there is no information

1. Platelet granules are responsible for forming thrombi.

2. There are more than three types of platelet granules.

3. a- granules are rich in biogenous amines.

4. d- granules also contain fibrinogen and fibronectin.

5. l- granules contain hydrolase.

6. A white thrombus is the same as an agglutination thrombus.

7. An agglutination thrombus is the same as Zahn thrombus.

8. Zahn thrombus is responsible for primary hemostasis in the vessels of diameters more than 50 -100 mcm.

9. Platelets trigger out spasm in the injured blood vessels.

10. Activation of platelets results in increase of sphyngomyelin content on their surface while its phosphatidylcholine content decreases.

11. Chronic thrombocytopenias result in regular reparation of blood vessels.

12. Platelets are responsible for stabilization of fibrin (XIII factor) and thrombus retraction.

13. Hemostasis in the vessels of diameters more than 50 -100 mcm takes place owing to the formation of an agglutination thrombus.

14. A coagulation thrombus consists of a head, a body and a tail.