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28 Cards in this Set
- Front
- Back
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What is the benefit of having fewer efferent than afferent lymphatics in lymph nodes?
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Having fewer efferents causes lymph to accumulate in lymph nodes, allowing more time for its cleansing.
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What are the general functions served by the lymphatic system?
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Lymphatic vessels, lymph nodes, and other lymphoid organs and tissues make up the lymphatic system. This system returns fluids that have leaked from the blood vascular system back to the blood, protects the body by removing foreign material from the lymph stream, and provides a site for immune surveillance.
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Describe the circulation of the lymphatic system.
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Lymphatic vessels form a one-way network - lymphatic capillaries, collecting vessels, trunks, and ducts - in which fluid flows only toward the heart. The right lymphatic duct drains lymph from the right arm and right side of the upper body. These ducts empty into the blood vascular system at the junction of the internal jugular and subclavian veins in the neck.
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Describe the flow of lymphatic fluid.
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The flow of lymphatic fluid is slow; it is maintained by skeletal muscle contraction, pressure changes in the thorax, and contractions of the lymphatic vessels. Backflow is prevented by valves.
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How permeable are lymphatic capillaries?
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Lymphatic capillaries are exceptionally permeable, admitting proteins and particulate matter from the interstitial space.
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What two types of detrimental body invaders can be spread by the lymphatic system?
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Pathogens and cancer cells may spread through the body via the lymphatic system.
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What types of cells might be found in the lymphatic system?
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The cells in lymphoid tissues include lymphocytes (immunocompetent cells called T cells or B cells), plasma cells (antibody-producing offspring of B cells), macrophages and dendritic cells (phagocytes and cells that initiate an immune response), and reticular cells that form the lymphoid tissue stroma.
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What kind of tissue makes up lymphoid tissue?
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Lymphoid tissue is reticular connective tissue. It houses macrophages and a continuously changing population of lymphocytes. It is an important element of the immune system.
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What are germinal centers, with respect to lymphoid tissue?
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Lymphoid tissue may be diffuse or packaged into dense follicles. Follicles often display germinal centers (areas where B cells are proliferating).
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What are the functions served by lymph nodes?
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Lymph nodes, the principal lymphoid organs, are discrete encapsulated structures containing both diffusely arranged and dense reticular tissue. Clustered among lymphatic vessels, lymph nodes filter lymph and help activate the immune system.
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What components comprise a lymph node?
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Each lymph node has a fibrous capsule, a cortex, and a medulla. The cortex contains mostly lymphocytes, which act in immune responses; the medulla contains macrophages, which engulf and destroy viruses, bacteria, and other foreign debris, as well as lymphocytes and plasma cells.
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Describe the flow of lymph via the lymph nodes.
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Lymph enters the lymph nodes via afferent lymphatic vessels and exits via efferent vessels. There are fewer efferent vessels; therefore, lymph flow stagnates within the lymph node, allowing time for its cleansing.
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How do lymph organs differ from lymph nodes?
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Unlike lymph nodes, the spleen, thymus, tonsils, and Peyer's patches do not filter lymph. However, most lymphoid organs contain both macrophages and lymphocytes.
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What are the functions served by the spleen?
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The spleen provides a site for lymphocyte proliferation and immune function, and destroys aged or defective red blood cells and bloodborne pathogens. It also stores and releases the breakdown products of hemoglobin as necessary, stores platelets, and acts as a hematopoietic site in the fetus.
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What is the function of the thymus?
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The thymus is most functional during youth. Its hormones cause T lymphocytes to become immunocompetent.
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What does MALT stand for? What does it do?
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Peyer's patches of the intestinal wall, lymphoid follicles of the appendix, tonsils of the pharynx and oral cavity, and follicles in the genitourinary and respiratory tract mucosa are known as MALT (mucosa-associated lymphatic tissue). They prevent pathogens in these passages from penetrating the mucous membrane lining.
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What tissue serves as the basis for lymphatic tissue and lymphoid organs during development?
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Lymphatics develop as outpocketings of developing veins. The thymus develops from endoderm, the other lymphoid organs derive from mesenchymal cells of mesoderm.
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What lymphoid organ develops first?
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The thymus, the first lymphoid organ to appear, plays a role in the development of other lymphoid organs.
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What do lymphocytes arise from?
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Lymphoid organs are populated by lymphocytes, which arise from heatopoietic tissue.
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Lymphatic vessels:
A) serve as sites for immune surveilance B) filter lymph C) transport leaked plasma proteins and fluids to the cardiovascular system D) are represented by vessels that resemble arteries, capillaries, and veins |
C) transport leaked plasma proteins and fluids to the cardiovascular system
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The saclike initial portion of the thoracic duct is the
A) lacteal B) right lymphatic duct C) cisterna chyli D) lymph sac |
C) cisterna chyli
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Entry of lymph into the lymphatic capillaries is promoted by which of the following?
A) one-way minivalves formed by overlapping endothelial cells B) the respiratory pump C) the skeletal muscle pump D) greater fluid pressure in the interstitial space |
A) one-way minivalves formed by overlapping endothelial cells
and D) greater fluid pressure in the interstitial space |
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The structural framework of lymphoid organs is:
A) areolar connective tissue B) hematopoietic tissue C) reticular tissue D) adipose tissue |
C) reticular tissue
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Lymph nodes are densely clustered in all of the following body areas except:
A) the brain B) the axillae C) the groin D) the cervical region |
A) the brain
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The germinal centers in lymph nodes are largely sites of:
A) macrophages B) proliferating B lymphocytes C) T lymphocytes D) all of these |
B) proliferating B lymphocytes
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The red pulp areas of the spleen are sites of:
A) venous sinuses, macrophages, and red blood cells B) clustered lymphocytes C) connective tissue septa |
A) venous sinuses, macrophages, and red blood cells
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The lymphoid organ that functions primarily during youth and then begins to atrophy is the:
A) spleen B) thymus C) palatine tonsils D) bone marrow |
B) thymus
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Collections of lymphoid tissue (MALT) that guard mucosal surfaces include all of the following except:
A) appendix follicles B) the tonsils C) Peyer's patches D) the thymus |
D) the thymus
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