Blood - argomento di esame

Granulocytes and Platelets

Granulocytes, which are also known as granular cells, are so called because their cytoplasm is made up of fine particles or granulations and include basophils, neutrophils and eosinophils. Neutrophils act in cases of acute inflammatory processes, as their task is to phagocytize (fagocitare) pathogens or cell detritus whereas eosinophils defend the body against parasites while basophils are reaction-to-allergy mechanisms.

Monocytes are cells involved in the generation of other highly-specialized cells with a macrophage function. Lymphocytes are classified into B and T lymphocytes; the former (i primi) are essential for the production of antibodies.

Platelets or thrombocytes derive from the fragmentation of megakaryocytes and they are essential in the haemostatic process. Three types of granules can be made out in platelets: α granules, dense granules, lysosomes.

Haemostasis and Blood Clotting

Haemostasis is the process which the blood vessels (vasi) arising (deriva,

è causata) from trauma. It may be(può essere) characterised of four phases:

1. Vascular phase in which the blood vessel starts contracting, reducing the size of their lumen and hence(quindi) loss of blood;
2. Platelet phase in which platelets are activated and plug the vessel;
3. Coagulation phase characterised by the formation of a network (rete) of fibres which stabilises the clot (coagulo);
4. Fibrin phase in which the normal structure of the vessel is restored and the clot removed.

Coagulation involves (coinvolge) a series of enzymes which activate thrombin. The latter changes fibrinogen into fibrin, that forms a network which traps platelets and red blood cells forming a clot.

Thrombin activation follows two different enzyme pathways (percorsi), the intrinsic and the extrinsic pathway.

Haematopoiesis

Haematopoiesis is a process of blood cell formation. By the third month stem cells colonize the liver (fegato), the primary site for blood cell formation.

bone marrow is the sole source of blood cells. There are two types of bone marrow: red bone marrow, which actively produces blood cells, and yellow bone marrow, which is inactive and fatty, mainly in old age. The main bones involved in haematopoiesis are the proximal epiphyseal regions of the humerus and femur, vertebrae, sternum, ribs, and pelvis. The haemopoietic process can be divided into various parts: - Erythropoiesis: the production of red blood cells - Granulocytopoiesis: the production of granulocytes - Monocytopoiesis: the production of monocytes - Lymphocytopoiesis: the production of lymphocytes - Thrombocytopoiesis: the production of plateletsincrease in red blood cell production, which helps to transport more oxygen to the tissues. In addition to erythropoietin, other factors such as iron, vitamin B12, and folic acid are also important for red blood cell production. Iron is necessary for the synthesis of hemoglobin, while vitamin B12 and folic acid are essential for DNA synthesis in red blood cell precursors. The process of red blood cell production, known as erythropoiesis, takes place in the bone marrow. It involves several stages, starting with the differentiation of HSCs into MEPs. Under the influence of BACH-1, MEPs commit to becoming erythroblast precursors. During erythropoiesis, the nucleus of the developing red blood cell is expelled, allowing more space for the accumulation of hemoglobin. This process is known as enucleation. Once mature, red blood cells are released into the bloodstream, where they circulate for about 120 days before being removed by the spleen. Overall, the production of red blood cells is a tightly regulated process that ensures the proper functioning of our body's oxygen transport system.