The Lymphoid System and Immunity

Vocabulary flashcards covering the structure, functions, fluid dynamics, and pathways of the lymphatic and immune systems based on Chapter 22 of Principles of Anatomy and Physiology.

Pathogens

Disease-producing microbes.

Immunity

The body’s ability to ward off damage or disease through natural defense.

Susceptibility

The body’s lack of resistance or vulnerability to a pathogen.

Nonspecific Resistance (Innate Immunity)

Defenses present at birth that provide general protection against invasion by a wide range of pathogens.

Adaptive Immunity

Immune response that involves the activation of specific lymphocytes (T and B cells) that combat a particular pathogen or other foreign substance.

Lymph

A fluid (about $3\,\text{L}$ per day) that flows within lymphatic vessels, circulates following the bloodstream (veins), and fights disease-causing agents.

Lymphatic System

The body system consisting of structures and organs containing lymphatic tissue, bone marrow, and lymph that carries out immune responses.

Functions of the Lymphatic System

1. Drains excess interstitial fluid and returns it to the blood to maintain blood volume; 2. Transports dietary fats and lipid-soluble vitamins; 3. Carries out immune responses by attacking abnormal cells.

Lymphatic Capillaries

Microscopic vessels that are closed on one end and located between cells of many tissues, serving as the beginning point of lymphatic vessels.

Lymphatic Vessels

Vessels formed by merging lymphatic capillaries that feature thin walls and numerous valves to direct the flow of lymph toward lymph nodes for filtration.

Lymph Nodes

Organs positioned along lymphatic vessels through which lymph passes to be filtered.

Lymph Trunks

Large vessels formed after lymph exits lymph nodes (including lumbar, intestinal, bronchomediastinal, subclavian, and jugular trunks) that drain various organs and body regions before merging into ducts.

Thoracic Duct

One of the two main collecting ducts formed by merging lymph trunks that returns lymph into the venous system.

Right Lymphatic Duct

One of the two main collecting ducts formed by merging lymph trunks that returns lymph from the upper right portion of the body into the venous system.

Areas Drained by Right Lymphatic and Thoracic Ducts

The right lymphatic duct drains the upper right quadrant of the body, whereas the thoracic duct drains the rest of the body including both lower limbs, the abdomen, and the left upper body.