Vocabulary - Lymphatic System

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1

Lymphatic System

The lymphatic System consists of three parts:

1.a meandering network of lymphatic vessels

2.lymph, the fluid contained in those vessels

3.lymph nodes that cleanse the lymph as it passes through them.

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Lymphatic vessels (Lymphatics)

Lymphatic vessels (Lymphatics)

an elaborate system of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

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Lymphatic Capillaries

Lymphatic Capillaries

The lymphatic transport system begins in microscopic blind-ended

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Lacteals

Lacteals

Highly specialized lymphatic capillaries are present in the fingerlike villi of the intestinal mucosa.

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Lymphatic Collecting Vessels

Lymphatic Collecting Vessels

Have the same three tunics as veins, but the collecting vessels are thinner walled, have more internal valves, and anastomose more.

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Lymphatic Trunks

Lymphatic Trunks

Formed by the union of the largest collecting vessels, and drain fairly large areas of the body.

Paired
lumbar trunks
bronchomediastinal trunks
subclavian trunks
jugular trunks

Single
intestinal trunk

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Right Lymphatic Duct

Right Lymphatic Duct

Drains lymph from the right upper limb and the right side of the head and thorax

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Thoracic Duct

Thoracic Duct

Receives lymph from most of the body except the right upper limb and the right side of the head and thorax

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Lymphedema

Lymphedema

Short-term severe localized edema

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Lymphoid (lymphatic) Tissue

Lymphoid (lymphatic) Tissue

Important component of the immune system
• houses and provides a proliferation site for lymphocytes
• furnishes an ideal surveillance vantage point for lymphocytes and macrophages.

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Lymphocytes

Lymphocytes

The main warriors of the immune system, mature into one of the two main varieties of immunocompetent cells that protect the body against antigens

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T cells

T cells

T lymphocytes
Manage the immune response, and some of them directly attack and destroy infected cells.

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B cells

B cells

B lymphocytes
Protect the body by producing plasma cells, daughter cells that secrete antibodies into the blood

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Antigens

Antigens

Anything the body perceives as foreign, such as bacteria and their toxins, viruses, mismatched RBCs, or cancer cells.

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Antibodies

Antibodies

Mark antigens for destruction by phagocytes or other means.

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Lymphoid Macrophages

Lymphoid Macrophages

Play a crucial role in body protection and in the immune response by phagocytizing foreign substances and by helping to activate T cells.

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Dendritic Cells

Dendritic Cells

Capture antigens and bring them back to the lymph nodes.

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Stroma

Network that supports the other cell types in the lymphoid organs and tissues

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Reticular Cells

Reticular Cells

Fibroblast-like cells that produce the reticular fiber stroma

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Diffuse Lymphatic Tissue

Diffuse Lymphatic Tissue

Consisting of a few scattered reticular tissue elements, is found in virtually every body organ, but larger collections appear in the lamina propria of mucous membranes and in lymphoid organs.

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Lymphoid Follicles (nodules)

Lymphoid Follicles (nodules)

They lack a capsule, but follicles are solid, spherical bodies consisting of tightly packed reticular elements and cells.

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Germinal Centers

Germinal Centers

Lighter staining center of lymphoid follicles where proliferating B cells predominate

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Lymph Nodes

Lymph Nodes

The principal lymphoid organs in the body, act as lymph “filters” and help activate the immune system.

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Lymph Capsule

Lymph Capsule

Dense fibrous tissue surrounding the lymph node

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Trabeculae

Trabeculae

Connective tissue strands extend inward from the capsule to divide the node into a number of compartments

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Lymph Node Cortex

Lymph Node Cortex

Outer area of node

Superficial part of the cortex contains densely packed follicles, many with germinal centers heavy with dividing B cells. Dendritic cells nearly encapsulate the follicles and abut the deeper part of the cortex, which primarily houses T cells in transit. The T cells circulate continuously between the blood, lymph nodes, and lymph, performing their surveillance role.

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Lymph Node Medulla

Lymph Node Medulla

Center area of node

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Medullary Cords

Medullary Cords

Thin inward extensions from the cortical lymphoid tissue, and contain both types of lymphocytes plus plasma cells.

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Lymph Sinuses

Lymph Sinuses

Large lymph capillaries spanned by crisscrossing reticular fibers. Numerous macrophages reside on these reticular fibers and phagocytize foreign matter in the lymph as it flows by in the sinuses.

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Afferent Lymphatic Vessels

Afferent Lymphatic Vessels

Vessels where lymph enters the node on convex side.

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Subcapsular Sinus

Subcapsular Sinus

Large, baglike sinus the lymph moves to after entering the node.

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Hilum

Hilum

The indented region on the concave side

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Efferent Lymphatic Vessels

Efferent Lymphatic Vessels

Vessels where lymph exits the node on concave side.

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Buboes

Buboes

Infected lymph nodes which are inflamed, swollen, and tender to the touch

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Spleen

Spleen

About the size of a fist and is the largest lymphoid organ. The spleen provides a site for lymphocyte proliferation and immune surveillance and response. Important are its blood-cleansing functions.

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White Pulp

White Pulp

Areas of the spleen composed mostly of lymphocytes suspended on reticular fibers , involved with the immune functions

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Red Pulp

Red Pulp

Essentially all remaining splenic tissue, that is, the venous sinuses (blood sinusoids) and the splenic cords, regions of reticular connective tissue exceptionally rich in macrophages. Red pulp is most concerned with disposing of worn-out red blood cells and bloodborne pathogens

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Thymus

Thymus

Important functions primarily during the early years of life. The thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.

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Thymic (Hassall’s) Corpuscles

Thymic (Hassall’s) Corpuscles

Consisting of concentric whorls of keratinized epithelial cells, they were thought to be sites of T cell destruction. Recent evidence suggests that Hassall’s corpuscles are involved in the development of a class of T lymphocytes called regulatory T cells, which are important for preventing autoimmune responses.

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Tonsils

The simplest lymphoid organs. They form a ring of lymphatic tissue around the entrance to the pharynx (throat), where they appear as swellings of the mucosa. The tonsils gather and remove many of the pathogens entering the pharynx in food or in inhaled air.

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Palatine Tonsils

Palatine Tonsils

Located on either side at the posterior end of the oral cavity. These are the largest of the tonsils and the ones most often infected.

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Lingual Tonsil

Lingual Tonsil

Lumpy collection of lymphoid follicles at the base of the tongue.

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Pharyngeal Tonsil

Pharyngeal Tonsil

(referred to as the adenoids if enlarged) is in the posterior wall of the nasopharynx.

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Tubal Tonsils

Tubal Tonsils

Surround the openings of the auditory tubes into the pharynx.

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Peyer’s Patches

Peyer’s Patches

Aggregated lymphoid nodules, are large clusters of lymphoid follicles, structurally similar to the tonsils. They are located in the wall of the distal portion of the small intestine

• destroy bacteria (which are present in large numbers in the intestine) before these pathogens can breach the intestinal wall

• generate many “memory” lymphocytes for longterm immunity.

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MALT

Mucosa-Associated Lymphatic Tissue (MALT)

Protects passages that are open to the exterior from the never-ending onslaughts of foreign matter entering them.

Appendix
Tonsils—all located in the digestive tract
Lymphoid follicles in the walls of the bronchi (organs of the respiratory tract)
Mucosa of genitourinary organs

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Elephantiasis

Elephantiasis

Typically a tropical disease in which the lymphatics (particularly those of the lower limbs and scrotum) become clogged with parasitic roundworms, an infectious condition called filariasis. Swelling (due to edema) reaches enormous proportions.

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Hodgkin’s Disease

Hodgkin’s Disease

A malignancy of lymphoid tissue; symptoms include swollen, nonpainful lymph nodes, fatigue, and often intermittent fever and night sweats. Characterized by presence of giant malignantly transformed B cells called Reed-Sternberg cells. Infection with Epstein-Barr virus and genetic susceptibility appear to be predisposing factors. Treated with chemotherapy and radiation; high cure rate.

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Lymphadenopathy

Lymphadenopathy

Any disease of the lymph nodes.

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Lymphangiography

Lymphangiography

Diagnostic procedure in which the lymphatic vessels are injected with radiopaque dye and then visualized with X rays.

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Lymphoma

Lymphoma

Any neoplasm (tumor) of the lymphoid tissue, whether benign or malignant.