Types of White Blood Cells

Infectious Agents and Exposure

• The body is continually exposed to infectious agents such as bacteria, viruses, fungi, and parasites.
• These infectious agents naturally occur in the environment, soil, water, and on various surfaces.

Consequences of Deep Tissue Invasion

• If infectious agents invade deeper tissues, they can cause severe infections, inflammation, and even systemic responses leading to sepsis.

White Blood Cells and Blood Clotting

• Platelets, a type of blood cell, are specifically responsible for activating the blood-clotting mechanism.

Formation of White Blood Cells

• Granulocytes and monocytes are formed in the bone marrow.
• Lymphocytes and plasma cells are primarily produced in lymphoid tissues, such as the lymph nodes and spleen.

Storage of White Blood Cells

• White blood cells are formed and stored in the bone marrow until they are needed in the circulatory system.

Myelocytic Lineage Function

• Myelocytic lineage plays a crucial role in the formation of granulocytes, which help in the immune response.

Megakaryocyte Formation

• Megakaryocytes are formed in the bone marrow and are responsible for producing platelets.

Lifespan of Platelets

• Platelets have a lifespan of about 7 to 10 days in the blood.

Storage of Lymphocytes

• Lymphocytes are mostly stored in the lymphatic system, particularly in the lymph nodes and spleen.

Function of Leukocytes

• The main function of leukocytes is to protect the body against infections and foreign substances.

Cell Types and Their Functions

• Cytotoxic T-cells possess the ability to 'seek out and destroy' foreign invaders such as infected cells and tumors.

Disease Prevention by Leukocytes

• Leukocytes prevent diseases through various mechanisms, including phagocytosis, production of antibodies, and release of cytokines.

Leukocyte Formation Sites

• Leukocytes are formed in the bone marrow and also in lymphoid tissues.

Granulocytes and Monocytes Role

• Granulocytes and monocytes play a key role in protecting the body by engulfing pathogens and releasing enzymes to destroy them.

Neutrophils and Macrophage Functions

• Neutrophils and tissue macrophages primarily function to engulf (phagocytize) bacteria and facilitate the inflammatory response.

Tissue Entry of White Blood Cells

• Neutrophils and monocytes enter tissue spaces through diapedesis, where they migrate out of blood vessels.

Movement Mechanism of White Blood Cells

• Both neutrophils and macrophages move through tissues using amoeboid movement, responding to chemical signals.

Attraction to Inflammation

• White blood cells are attracted to inflamed tissue areas due to the release of cytokines and chemokines from damaged cells.

Neutrophils and Bacteria

• The main function of neutrophils and macrophages in relation to bacteria is phagocytosis and destruction of pathogens.

Phagocytosis Process

• The process whereby a pathogen is selected for phagocytosis and destruction is called opsonization.

Phagocytosis Capacity

• A single neutrophil can typically phagocytize around 5 to 25 bacteria before becoming inactivated and dying.

Macrophage Functionality

• Macrophages mainly function within tissues by phagocytizing pathogens and debris, and presenting antigens to T-cells.

Total Monocyte Variants

• The total combination of monocytes, mobile macrophages, fixed tissue macrophages, and specialized endothelial cells in the bone marrow, spleen, and lymph nodes is called the mononuclear phagocyte system.

Local Tissue Macrophage Response

• Local tissue macrophages can divide in situ and form more macrophages when an infection begins in a subcutaneous tissue.

Fate of Foreign Particles in Lymph Nodes

• Foreign particles that enter the lymph nodes are trapped and processed by resident macrophages.

Common Routes of Infection

• Invading organisms frequently enter the body through mucosal surfaces, such as the respiratory and gastrointestinal tracts.

Kupffer Cells Function

• Kupffer cells, tissue macrophages in the liver, act as a defense against bacteria from ingested food.

Reticular Meshwork Entrapment

• Macrophages become entrapped by the reticular meshwork in tissues when foreign particles come into contact with them.