BRAINCAKEAgranulocytes
Agranulocytes are leucocytes with no visible granules in their cytoplasm and a nucleus that is not lobed. They make up about 30% of all leucocytes. There are two types: monocytes and lymphocytes.
Monocytes
• the largest leucocytes, up to about 20 µm across
• large kidney-shaped (bean-shaped) nucleus
• about 2 to 8% of leucocytes
• circulate in the blood for a day or two, then leave the capillaries and enter the tissues, where they develop into macrophages
• macrophages are long-lived phagocytes that engulf pathogens and debris. After digesting a pathogen they display its antigens on their surface, acting as antigen-presenting cells that activate lymphocytes
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Key terms in this lesson
- antibody
- A protein produced by B lymphocytes (plasma cells) that binds specifically to an antigen, helping to destroy pathogens.
More in Circulatory Systems
- Plasma
- Erythrocytes
- Leucocytes
- Granulocytes
- Platelets
- Haemoglobin and Oxygen Transport
- Oxygen Dissociation Curve for Haemoglobin
- The Bohr Effect
All 33 lessons in Circulatory Systems · All Edexcel AS-level Biology topics