Untitled Quiz

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@HilariousTheory

Study Notes

The lymphatic system and lymphoid tissues work together to maintain cardiac function and protect the body from infection.
The lymphatic system returns fluids leaked from the vasculature back into circulation.
Lymph, a fluid, travels through lymphatic vessels.
Lymph nodes cleanse the lymph as it passes.
Lymphoid tissues/organs are the structural basis of the immune system.
These include the spleen, thymus, and tonsils.

Fluid is pushed out of circulation by hydrostatic and colloid osmotic pressures at capillary beds.
Approximately 3 liters of fluid daily becomes interstitial fluid.
This fluid is reabsorbed by the lymphatic system to maintain blood volume.
Absorbed fluid is called lymph.
Lymphatic vessels have valves to prevent backflow.
Lymphatic capillaries are highly permeable, allowing fluids, proteins, and large particles to enter.
These capillaries have overlapping endothelial cells that act as one-way valves.
Specialized lymphatic capillaries called lacteals absorb fat in the small intestine.

Lymphatics have no pump mechanism.
Lymph movement is aided by skeletal muscle contractions, pressure changes in the thorax during breathing, valves that prevent backflow, pulsation of nearby arteries, and rhythmic contractions of lymphatic vessel smooth muscle.
Lymph movement is sporadic and slow.

All immune system cells and supporting cells in lymphoid tissues are lymphocytes—the main warriors of the immune system.
These originate from bone marrow.
T cells (T lymphocytes) are managers of the immune response.
B cells (B lymphocytes) may mature into plasma cells and produce antibodies.
Macrophages phagocytose foreign materials and activate T cells.
Dendritic cells are superior at antigen presentation.
Reticular cells produce stroma, supporting other cells in lymphoid organs.

Lymphoid tissues/organs have two major functions: providing a site for lymphocyte proliferation and serving as a vantage point for surveillance by lymphocytes and macrophages.
Lymphoid tissue is found in virtually all organs.
Lymphoid follicles (nodules) are solid spherical bodies of reticular fibers and lymphoid cells.
Some lymphoid follicles are part of larger organs, whereas others are in non-lymphoid tissues (like Peyer's patches).
Examples of lymphoid organs: tonsils, thymus, spleen, Peyer's patches, appendix.

Lymph nodes are clustered around lymphatic vessels.
Lymph nodes have two main functions: filtration and immune system activation.
Lymph nodes have an external fibrous capsule and trabeculae that divide the node into compartments.
The cortex contains follicles (mostly B cells) with germinal centers.
The medulla contains lymphocytes and macrophages.
Lymph enters through afferent lymphatic vessels and exits through efferent lymphatic vessels.

The spleen is the largest lymphoid organ, acting as a filter for blood.
It cleanses blood of old/defective erythrocytes and platelets, removes debris, stores iron salvage & platelets for release, and may be a site of fetal erythrocyte production.
White pulp in the spleen contains many lymphocytes.
Red pulp in the spleen is responsible for erythrocyte and pathogen destruction.
The thymus is the site of T lymphocyte maturation (T cell maturation). Its activity decreases with age. The thymus is largely a site for T-cell development and maturation.
MALT (Mucosa-associated lymphoid tissue) is diffuse lymphoid tissue found in the mucosa of many organs. MALT helps to capture and destroy pathogens that enter the mucosa from air, food & drinks. Examples of MALT include tonsils, Peyer's patches, and the appendix.