Thrombosis

What factors are included in the classical Virchow's triad?

The classical Virchow's triad includes three main pathogenetic factors contributing to the activation of thrombogenesis.

• Vascular wall injury — disruption of endothelial structure and function (due to trauma, infections, or atherosclerosis).
• Slowing of blood flow — stasis or venous congestion (e.g., in heart failure or immobilization).
• Hypercoagulability — increased blood clotting capacity and suppression of fibrinolysis.

What biologically active substances do platelets release upon degranulation during thrombogenesis?

During degranulation and the release reaction, platelets secrete biologically active substances involved in thrombogenesis. These include:

• ADP — released upon platelet activation and stimulates neighboring platelets via purinergic receptors.
• Thromboxane A2 — exerts a vasoconstrictive effect, slows blood flow, and enhances platelet aggregation.
• Serotonin.
• Histamine.
• Platelet-derived growth factor.
• Platelet coagulation factors, including thromboplastin, which initiates coagulation hemostasis.

What types of thrombi are distinguished based on their macroscopic structure and composition?

Depending on macroscopic structure and composition, four main types of thrombi are distinguished.

What are the favorable and unfavorable outcomes of thrombosis?

Thrombosis outcomes are divided into two main groups.

Favorable outcomes:

• Organization of the thrombus — replacement by connective tissue.
• Canalization — formation of channels within the thrombotic masses.
• Vascularization — ingrowth of blood vessels into the thrombus.
• Calcification — deposition of calcium salts (phleboliths form in veins).
• Ossification — formation of bone tissue.
• Aseptic autolysis — dissolution of the thrombus by the fibrinolytic system.

Unfavorable outcomes:

• Thromboembolism — detachment of the thrombus or its part.
• Septic softening — occurs when pyogenic bacteria invade the thrombus.

In which vessels do red thrombi predominantly form?

Red thrombi predominantly form in veins. The process of their formation occurs rapidly and under conditions of slow blood flow. By composition, such a thrombus includes erythrocytes, fibrin, and platelets. Examples of venous thrombosis include marantic thrombus, which forms during venous stasis against the background of dehydration and hemoconcentration, as well as thrombi in polycythemia vera.

What macroscopic parts (sections) does a mixed thrombus consist of?

A mixed thrombus consists of three macroscopic sections.

• Head — structurally represents a white thrombus, tightly attached to the vessel wall.
• Body — the mixed thrombus proper, having a layered structure.
• Tail — structurally corresponds to a red thrombus, loosely attached to the intima. This is the part that most commonly detaches, becoming a thromboembolus.