Blood Cells
Blood Cells
Leukocytes (WBC’s)
Leukocytes also known as white blood cells (WBCs) are cells which play a defensive roll in the body against injury and infection. They migrate towards tissues where they are needed and become functional performing various activities. WBCs can be divided into 2 groups: Polymorphonuclear granulocytes and mononuclear agranulocytes. Both types are spherical while suspended in blood plasma but when they invade tissues after leaving the blood vessels they become amoeboid and motile. The sizes referred to in the diagrams are as observed in blood smears (where cells are spread out, here they can appear slightly larger than they are when in circulation in the blood plasma). Granulocytes have 2 types of granules:
• Specific granules – these have specific functions and bind to several stains (neutral, basic or acidic)
• Azurophilic granules – these are specialized lysosomes which stain darkly and are present at some level in all forms of leukocytes.
When WBCs phagocytise microorganisms many azurophilic granule proteins work together to kill and digest the microorganisms. Bacterial proteins include:
• Myeloperoxidase – which generates hypochlorite and other reactive agents which are toxic to bacteria
• Defensins – which bind and produce holes in cell membranes of microorganisms
• Lysozymes – which dissolve the components of the walls of bacterial cells
Granulocytes contain nuclei with two or more lobes including – neutrophils, eosinophils and basophils. These terminally differentiated cells only have a life span of a few days. They have poorly developed Golgi complexes and rough ER and they contain only a few mitochondria. Leukocytes depend largely on glycolysis for their low energy requirements this allows them to function in tissue which has little oxygen present e.g. inflamed areas. These cells usually die by apoptosis in the connective tissue. Billions of neutrophils die apoptotic deaths every
Leukocytes (WBC’s)
Leukocytes also known as white blood cells (WBCs) are cells which play a defensive roll in the body against injury and infection. They migrate towards tissues where they are needed and become functional performing various activities. WBCs can be divided into 2 groups: Polymorphonuclear granulocytes and mononuclear agranulocytes. Both types are spherical while suspended in blood plasma but when they invade tissues after leaving the blood vessels they become amoeboid and motile. The sizes referred to in the diagrams are as observed in blood smears (where cells are spread out, here they can appear slightly larger than they are when in circulation in the blood plasma). Granulocytes have 2 types of granules:
• Specific granules – these have specific functions and bind to several stains (neutral, basic or acidic)
• Azurophilic granules – these are specialized lysosomes which stain darkly and are present at some level in all forms of leukocytes.
When WBCs phagocytise microorganisms many azurophilic granule proteins work together to kill and digest the microorganisms. Bacterial proteins include:
• Myeloperoxidase – which generates hypochlorite and other reactive agents which are toxic to bacteria
• Defensins – which bind and produce holes in cell membranes of microorganisms
• Lysozymes – which dissolve the components of the walls of bacterial cells
Granulocytes contain nuclei with two or more lobes including – neutrophils, eosinophils and basophils. These terminally differentiated cells only have a life span of a few days. They have poorly developed Golgi complexes and rough ER and they contain only a few mitochondria. Leukocytes depend largely on glycolysis for their low energy requirements this allows them to function in tissue which has little oxygen present e.g. inflamed areas. These cells usually die by apoptosis in the connective tissue. Billions of neutrophils die apoptotic deaths every