, or white blood cells, are the body's defense squad. They fight off invaders like bacteria and viruses, keeping us healthy. Each type of has a unique role in the , from that gobble up pathogens to that remember past infections.
are tiny cell fragments that spring into action when we're injured. They stick together to form clots, stopping bleeding and helping wounds heal. Understanding how work is key to grasping how our bodies protect themselves and repair damage.
Leukocytes
Characteristics and functions of leukocytes
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Leukocytes and Platelets | Anatomy and Physiology II View original
Leukocytes, or white blood cells (WBCs), are essential components of the immune system that defend the body against infectious agents (bacteria, viruses) and foreign substances
Leukocytes can exit the bloodstream and migrate to tissues where they are needed to fight infections or
Leukocytes are categorized into (, , ) which contain granules in their cytoplasm, and (lymphocytes, ) which lack granules
Leukocytes are produced in the through , where they originate from and differentiate into specific types based on the presence of and growth factors
Types of leukocytes in immune response
Neutrophils (50-70% of leukocytes)
Possess a multilobed nucleus and fine, pale pink granules in the cytoplasm
Primary role is of bacteria and fungi, serving as the first responders to sites of infection or inflammation
(2-4% of leukocytes)
Have a bilobed nucleus and large, coarse, reddish-orange granules in the cytoplasm
Involved in allergic reactions, defense against parasites, and release enzymes that neutralize inflammatory chemicals
(0.5-1% of leukocytes)
Contain a lobed nucleus and large, dark blue-purple granules in the cytoplasm
Release and other inflammatory mediators during allergic reactions, contributing to the inflammatory response
Lymphocytes (25-35% of leukocytes)
Characterized by a large, round nucleus with a thin rim of cytoplasm
Two main types: for cell-mediated immunity (direct attack on infected or cancerous cells) and for humoral immunity (antibody production)
Play a crucial role in recognizing and responding to specific
(3-8% of leukocytes)
Feature a large, kidney-shaped nucleus and abundant pale-blue cytoplasm
Migrate into tissues and differentiate into and
Phagocytose pathogens, cellular debris, and foreign substances, and present antigens to lymphocytes to initiate specific immune responses
Immune System and Inflammation
The immune system is a complex network of cells, tissues, and organs that work together to defend the body against pathogens and foreign substances
Inflammation is a protective response of the immune system to injury or infection, characterized by redness, swelling, heat, and pain
Bone marrow plays a crucial role in the immune system by producing and maturing various types of immune cells
Platelets and Hemostasis
Structure and function of platelets
Platelets () are small, disc-shaped cell fragments derived from in the bone marrow through a process of fragmentation
Platelets lack a nucleus but contain organelles, granules, and enzymes essential for their function in (stopping bleeding and repairing damaged blood vessels)
involves three main stages:
Vascular spasm
Platelet plug formation
Coagulation (blood clotting)
When a blood vessel is injured, platelets adhere to the damaged , become activated, and release granules containing clotting factors and growth factors
Activated platelets change shape and aggregate to form a platelet plug, sealing the damaged vessel
Platelets also contribute to the coagulation cascade by providing a surface for the assembly of clotting factors which convert into , forming a mesh-like network that stabilizes the platelet plug and creates a solid clot
Disorders of leukocytes and platelets
Leukocyte disorders:
Leukopenia: low leukocyte count, increases susceptibility to infections, caused by medications, autoimmune disorders, or bone marrow disorders
: high leukocyte count, often a sign of infection, inflammation, or , caused by stress, smoking, or certain medications
: blood cancer, uncontrolled production of abnormal leukocytes, impairs normal blood cell production and function, leads to anemia, infections, and bleeding disorders
Platelet disorders:
: low platelet count, increases risk of bleeding and impairs clotting, caused by autoimmune disorders, medications, or bone marrow disorders
: high platelet count, increases risk of blood clots and thrombosis, caused by , iron deficiency, or certain cancers
Platelet dysfunction: impaired platelet function despite normal count, can be inherited or acquired, leads to prolonged bleeding time and impaired clot formation, caused by medications (aspirin, NSAIDs)