4. Some are capable of phagocytosis (neutrophils, eosinophils and monocytes).
50-70% of all WBC's
Their cytoplasm is packed with pale granules containing lysosomal enzymes and bacteria killing compounds. The breakdown of used neutrophils in an infected wound forms pus.
2-4% of all WBC's
Their mode of attack is the excrete toxic compounds such as nitric oxide and cytotoxic enzymes, which are effective against parasites that are too large to engulf. Also Eosinophils are sensitive to allergenad and increase during allergic reactions. They release enzymes that counteract the inflammatory effects of neutrophils and mast cells.
<1% of WBC's
Small; accumulate in damaged tissue and release histamine, which dialates blood vessels and heparins, which prevents blood clotting.
2-8% of WBC's
Large; they become macrophages to engulf large particles and pathogens.
20-30% of WBC's
Migrate in and out of the blood. Spend most of their time in connective tissues and lymphatic organs.
T-Cells - attack foreign cells directly.
B-Cells differentiate into plasma cells which synthesize antibodies
NK natural killer cells - detect and destroy abnormal tissue cells, such as cancer.
Where are white blood cells
All WBC's except monocutes develop fully in the bone marrow. (Monocytes develop into macrophages in peripheral tissues).
All WBC's originate from hemoblasts:
Hemoblasts -> Myeloid Stem Cells -> Progenitor Cells -> All other WBC's
Hemoblasts -> Lymphoid Stem Cells -> Lymphocytes
What are platelets and their 3 main functions?
Platelets are cell fragments involved in the clotting system.
1. Release of chemicals inportant to the clotting process
2. Formation of a temporary patch in the walls of damaged blood vessels
3. Active tissue contraction after clot formation has occurred.
How are platelets formed?
Thrombocytopoiesis occurs in bone marrow. Giant cells called megakaryocytes manufacture platelets by shedding cytoplasm packets until they are used up. The process is controlled by thrombopoietin (TPO).