Dynamic Study Module Chapter 20 Flashcards

Mucosa-Associated Lymphatic Tissue (MALT)

• MALT stands for mucosa-associated lymphatic tissue, crucial for protecting mucous membranes from pathogens.
• Found in the gastrointestinal tract, respiratory passages, and to a lesser extent, in the genitourinary tract.
• Key locations of MALT include tonsils, Peyer's patches in the ileum, and the appendix.
• Non-MALT lymphatic organs include the liver, kidneys, and spleen.

Thymus and T Lymphocytes

• The thymus is essential for developing functional T lymphocytes (T cells) crucial for the immune response.
• Unlike other lymphoid organs, the thymus does not trap pathogens; its primary role involves hormone secretion to stimulate T cell maturation.

Interferons and Immune Responses

• Interferons are cytokines that impede pathogen infection in host cells, primarily during viral infections.
• They activate components of both innate and adaptive immunity, enhancing the immune response through various mechanisms, including stimulating neighboring cells.

Acquired Immunity

• Acquired immunity, also known as adaptive immunity, provides immunological memory through lymphocyte response to specific antigens.
• This immunity is slower in response but becomes dominant after initial exposure and is characterized by memory for rapid future responses.

Lymphatic Vessels and Nodes

• The only lymphatic organ equipped with afferent lymphatic vessels is the lymph node.
• Lymph nodes filter lymph through structures that trap pathogens and activate immune cells.

Surface Barriers as First Line of Defense

• The first line of defense includes cutaneous and mucous membranes, offering a physical barrier to pathogen entry.
• Surface barriers are followed by innate immunity responses, and then adaptive immunity as a third defense line.

Lymph Fluid and Composition

• Lymph, found in lymphatic vessels, is derived from interstitial fluid and is crucial for returning excess fluid to the circulatory system.
• The loss of 2-4 liters of fluid daily necessitates this transport mechanism to maintain blood volume and pressure.

Immune System Overview

• The immune system lacks specific organs but involves cells and proteins located in blood and other tissues, collaborating closely with the lymphatic system.
• It functions effectively against internal and external threats, exhibiting both innate and acquired responses.

Flow of Lymph from Lower Body

• Lymph from the right leg travels through the right lumbar trunk, cisterna chyli, thoracic duct, and drains into the left subclavian vein.

Antigen-Presenting Cells

• Antigen-presenting cells, such as macrophages, display ingested pathogens on their membranes, activating T cells and facilitating an immune response.

Lacteals and Dietary Fats

• Lacteals are specialized lymphatic capillaries in the small intestine that absorb dietary fats, allowing fat breakdown products to enter lymphatic circulation.

Pyrogens and Fever Response

• Pyrogens act on the hypothalamus, resetting the body's temperature thermostat to facilitate the immune response during infections, often leading to fever symptoms.

Lymphatic Drainage from Thoracic Cavity

• Bronchomediastinal trunks drain lymph from the thoracic cavity, while other trunks serve different parts of the body, highlighting the specificity of lymphatic drainage.

Composition Similarity

• Lymph is most similar in composition to interstitial fluid, as it originates from fluid that exits the extracellular space.

Cell Types in Lymphoid Tissues

• Lymphoid tissues primarily consist of lymphocytes (B and T cells), macrophages, and dendritic cells, whereas chondrocytes, associated with cartilage, are absent in these tissues.### Dendritic Cells and Reticular Cells
• Dendritic cells are spiny leukocytes crucial for lymphocyte activation.
• Reticular cells produce reticular fibers, a specialized thin type of collagen protein.
• Reticular cells are abundant in the spleen and lymph nodes, contributing to their structure.

Cytokines and Innate Immunity

• Opsonins, such as the complement protein C3b, enhance phagocytosis but are not cytokines.
• Innate immunity responds uniformly to all pathogens and is activated quickly within the first 12 hours post-exposure.
• Cytokines like tumor necrosis factor (TNF), interferons, and interleukins play a role in modulating the immune response.

Inflammation Response

• Cardinal signs of inflammation include redness, heat, swelling (edema), and pain, excluding cold.
• The inflammatory response involves damaged cells releasing mediators and phagocyte activity for tissue cleanup.

Tonsils and Crypts

• Deep indents in the tonsils called crypts trap bacteria and debris, often resulting in tonsillitis due to frequent pathogen exposure.

Interleukins

• Interleukins (IL), a class of 29 cytokines, facilitate communication between leukocytes and are key in stimulating immune responses.

Immune Cell Origin

• All immune cells in the lymphatic system originate from red bone marrow, which produces leukocytes, leading to leukocytosis during responses.

Pus Formation

• Pus, a whitish mixture of dead leukocytes, dead tissue cells, and fluid, forms as neutrophils and macrophages digest pathogens.

Leukocytosis Timeline

• Occurs 3-4 days after tissue damage due to cytokine activity stimulating leukocyte production in the bone marrow.

Second Line of Defense

• The second line of defense is composed of innate immunity cells and proteins which respond quickly to a wide array of pathogens.

Eosinophils and Parasitic Infections

• Eosinophils are effective against parasitic pathogens by releasing granule contents to damage and neutralize parasites.

Thymus Functionality with Age

• The thymus, largest in childhood, atrophies with age, leading to a significant decrease in T cell production by age 65.

Lymphatic System Functions

• The lymphatic system regulates interstitial fluid volume, absorbs dietary fats through lacteals, and provides immune functions by filtering pathogens from lymph.

Cisterna Chyli

• This structure receives lymph from the intestinal and lumbar trunks, draining into the thoracic duct which connects to major venous systems.

Adaptive Immunity

• Lymphocytes (B and T cells) are pivotal in adaptive immunity, which has the capacity for immunological memory against specific antigens.

Lymph Node Functions

• Lymph nodes filter pathogens from lymph through afferent vessels, trapping them in the reticular network, and facilitating immune response.

Spleen and Blood Pathogen Protection

• The spleen acts as a major defense organ against pathogens in the blood, filtering through macrophages and dendritic cells.

Lymphatic Ducts Drainage

• Lymph from the thoracic and right lymphatic ducts empty into the subclavian veins, facilitating the return to the bloodstream.

Subclavian Trunks

• The subclavian trunks are responsible for collecting lymph from the upper limbs, with several lymph trunks draining different body regions.

Thymus and Immune Function

• Removal of the thymus severely affects immune functions in infants due to its critical role in T cell production during early life.### Immune System Components and Functions
• Neutrophils play a crucial role in innate immunity through respiratory burst, escalating oxygen consumption to produce chemicals like hydrogen peroxide that kill pathogens.
• Natural Killer (NK) cells enhance immune response by recognizing and destroying abnormal or infected cells, and they release cytokines to activate macrophages.
• Cytotoxic T cells (TC cells) specialize in targeting and eliminating invaded or cancerous cells through recognition of antigens presented on class I MHC molecules.
• Basophils, a rare type of granulocyte, mediate inflammation and are primarily found in the blood; mast cells are their related counterpart in mucous membranes.

Lymphatic System and Organs

• The spleen contains both red pulp, which clears old erythrocytes, and white pulp, which filters pathogens and contains leukocytes.
• The thymus is essential for T-lymphocyte maturation, enabling them to effectively respond to pathogens by generating functional T cell populations.
• Clusters of lymph nodes, including axillary lymph nodes under arms, serve as filters to trap pathogens and limit their spread throughout the body.
• Peyer's patches, specialized clusters of MALT, are located in the small intestine's ileum, playing a crucial role in gut immunity.

Immune Responses and Antibody Functions

• Antibodies are not considered surface barriers; surface barriers like skin and mucous membranes form the first line of defense against pathogens.
• The primary immune response peaks after 7-14 days, while the secondary immune response is more rapid, peaking within 3-5 days due to the presence of memory cells.
• Antibody functions include agglutination, opsonization, neutralization, and complement activation, without functioning directly in phagocytosis.

HIV and Immune Surveillance

• HIV specifically targets Helper T (TH) cells due to their CD4 molecules, leading to the decline of these cells in AIDS, which drastically impairs the immune response.
• Immune surveillance by T cells and NK cells is crucial for detecting and eliminating tumor cells, thereby preventing cancer development.

Antibody Types and Functions

• IgG constitutes 75-80% of circulating antibodies, is pivotal in fetal immunity, and provides long-term protection.
• IgA, primarily found in mucosal areas and secretions, plays a vital protective role in mucosal immunity.
• IgM is the largest antibody and is the first to respond to initial infections.

Cancer Cell Characteristics

• Cancer cells result from mutations leading to loss of differentiation, cell cycle control, and adherence to surrounding tissues, allowing for uncontrolled growth and potential metastasis.

Test your knowledge with flashcards from Chapter 20 of the Dynamic Study Module. This quiz covers crucial concepts related to the lymphatic system, including MALT and its significance in protecting mucosal membranes. It’s designed to enhance your understanding and retention of important terms.