Organs of the Immune System Flashcards
The ___________ system is a collection of vessels, tissues, and organs.
Lymphatic
Lymph fluid flows through the vessels, eventually draining into the ________.
Heart
The lymphatic systems plays a major role in immunity, is part of the circulatory system, and is important for fat _________ and fluid balance.
Absorption
The vessels include the smaller, tubular vessels called lymph ___________, and the larger collecting vessels, such as the right and left (thoracic) collecting ducts.
Capillaries
As blood circulated under pressure, its fluid component seeps through the capillaries, with in excess of ____L being lost every 24 hours.
2.9
The seepage is called ________ fluid.
Intersitital
Much fluid is returned to the blood, and the remainder is absorbed in the lymph capillaries, becoming _______.
Lymph
Much fluid is returned to the blood, and the remainder is absorbed in the lymph capillaries, becoming _______.
Lymph
The cells of the lymph are mostly _____________.
Lymphocytes
The lymphatic vessels then propel lymph into the right and left (thoracic) __________ _______.
Lymphatic ducts
The________ duct drains into the left subclavian vein (75% of lymph); the right lymphatic duct drains into the right subclavian vein (25% of lymph).
Thoracic
Name two primary lymphoid organs.
Bone marrow and thymus
Which primary lymphoid organ does the following passage describe? Each lobe is arranged into lobules of a cortex and medulla. Trabeculae separates the lobules. The cortex, or outer compartment, is densely packed with thymocytes. The medulla is more scarcely populated, with mostly mature T-cells. Hassall’s corpuscles contain degenerating epithelial cells. Scattered throughout are nonlymphoid epithelial cells (nurse cells), bone marrow-derived macrophages, and interdigitating dendritic cells (located at cortico-medullary junctions).
Thymus
The thymus reaches its maximum size at _______, before atrophying with a decrease in cortical and medullary cells, and an increase in the total fat content of the organ.
Puberty
________ syndrome is a rare genetic disorder, caused by mutations of Chromosome 22, required for thymic development. It results in almost complete T-cell deficiency, and an absence of cell-mediated immunity.
DiGeorge
Outline the thymic generation of T-cells.
Early lymphoid progenitors arrive from the bone marrow, enter into the thymus, and complete their immunogenic education, before leaving as fully-functional T-cells. They learn to differentiate between self and foreign antigens, with many potentially self-reactive T-cells being destroyed along the way. Maturing thymocytes undergo a series of distinct changes in T-cell receptor genes, expression of the T-cell receptor, expression of CD4 and CD8, and others. Earliest cell population arriving in the thymus lacks T-cell markers, and is double-negative CD4-CD8-. As the T-cell moves through the thymus, it matures into double-positive T-cell CD4+CD8+, and rearranges T-cell receptor genes to give rise to a T-cell receptor. Maturing T-cells undergo positive and negative selection, and then there is loss of either CD4 or CD8. Result is the expression of mature, single positive CD4+ or CD8+ T-cells, which exit via the medulla. Positive selection occurs when T-cells mature into double-positive phenotype, bearing both CD4 and CD8 molecules in the cortex. This allows for further maturation of T-cells into single positive cells, and is based on the ability of double-positive T-cells to bind to self MHC complexes, expressed by cortical epithelial cells. Negative selection occurs in the medulla; T-cells become single positive, expressing only CD 4 or CD8. Here, T-cells bind to MHC. Negative and positive selection is mediated by avidity of T-cells to bind to MHC antigens.
Regions of the bone marrow serve as the _______ equivalent, where B-cell maturation occurs.
Bursal
