Lymphatic System Overview

Created by

@WellEstablishedHeliotrope9485

Study Notes

Thymus

A single, unpaired gland located in the mediastinum.
Primary gland of the lymphatic system, producing thymosin hormone.
Stimulates red bone marrow to generate T lymphocytes (T cells).
Facilitates the development of T lymphocytes before they migrate to lymph nodes and spleen.

Lymph Nodes and Vessels

Drain fluid from tissues and return it to blood supply.
Transport lymph; filter and phagocytize antigens.
Generate monocytes and lymphocytes; develop antibodies essential for immunity.
Lymphocytes are key immune system defenders, monitoring for antigens.

Spleen

Largest lymphatic organ; removes damaged erythrocytes through macrophages.
Stores blood and platelets; filters and purifies blood.

Tonsils and Mucosal Tissues

Defend against microorganisms and harmful substances entering through the mouth and nose.

Peyer’s Patches

Located in the wall of the small intestine (ileum).
Part of small lymphoid tissues collection.

Kupffer Cells

Also called Browicz-Kupffer cells; fixed macrophages in the liver.
Protect upper respiratory tract and gastrointestinal tract from foreign invaders.

Specific Immunity

Humoral Immunity (Antibody-Mediated)

Involves antibodies found in body fluids, produced by B lymphocytes.
Characterized by antibody production in response to specific antigens.
B cells transform into plasma cells, producing immunoglobulins (antibodies).
Key antibody classes: IgG, IgA, IgM, IgE.
Mechanisms of action include neutralization, lysis, and opsonization.

Cellular Immunity (Cell-Mediated)

T lymphocytes defend the body directly.
Helper T cells activate the immune response; stimulate proliferation of B and other T cells.
Cytotoxic T cells directly attack antigens, lysing them.
Memory T cells remember specific antigens for rapid response upon re-exposure.
Suppressor T cells regulate and suppress immune responses to prevent overactivity.

Comparison of Immunity Types

Humoral Immunity: Involves B lymphocytes, produces antibodies, effective against extracellular pathogens (e.g., bacteria).
Cellular Immunity: Involves T lymphocytes, produces sensitized cells, effective against intracellular infections (e.g., viruses, fungi).

Non-Specific Immunity

Provides general defense against harmful agents; discriminates self from non-self.
Includes physical barriers (skin, mucous membranes), chemical barriers (acidic secretions), and biological response modifiers like interferons.

White Blood Cells in Non-Specific Immunity

Neutrophils are first responders in inflammation.
Eosinophils and basophils are activated during allergic reactions.
Monocytes/macrophages engage in phagocytosis of foreign substances.

Inflammatory Response

Initiated by tissue injury or pathogens; includes vasodilation and increased permeability.
Cardinal signs: redness, heat, swelling, pain, and loss of function.
Involves the release of chemical mediators and recruitment of leukocytes.

Phagocytosis Steps

Recognition: Phagocytic cells identify non-self or debris.
Ingestion: Cell membrane engulfs target, forming a vacuole.
Phagosome Formation: Granules release enzymes to destroy target.
Degradation: Target is broken down into smaller debris particles.

Cardinal Signs of Inflammation

Redness (rubor)
Heat (calor)
Swelling (tumor or turgor)
Pain (dolor)
Loss of function (functio laesa)

Stages of Inflammatory Response

Vascular Phase: Initial vasoconstriction followed by increased blood flow and swelling.
Cellular Exudate: Increase in circulating neutrophils and formation of pus; neutrophilia occurs.

In summary, the immune system comprises various specialized cells and organs working together to recognize and eliminate harmful agents, with both specific and non-specific mechanisms contributing to overall defense.