The Lymphatic System

Flashcards about the Lymphatic System

Lymphatic System

Aka the lymphoid system. Composed of organs, vessels, cells and tissues that help the body remain healthy (maintain homeostasis).

Lymphatic System

An extensive network of branching vessels, lymph nodes, bone marrow, thymus, spleen, appendix, and tonsils.

Lymph Nodes

Structures found along the vessels filled with a mesh of fibers and WBCs.

Lymph

Fluid that is pushed from the blood into tissue surrounding the capillaries and is carried by lymphatic vessels.

Nonspecific Defenses

Anatomical barriers and mechanisms that prevent or slow the entry of pathogens or attack them; they do not distinguish threats.

Specific Defense

The immune system, involving the lymphatic system.

Function of the Lymphoid System

Production, maintenance, and distribution of lymphocytes for defense against infections and hazards.

Lymphatic Vessels

Carry lymph from peripheral tissue to the venous system.

Lymphatic Capillaries

Smallest lymphatic vessels that branch through peripheral tissues, originating as pockets with larger diameters and thinner walls than blood capillaries.

Superficial Lymphatics

Located in the subcutaneous layer and mucus membranes lining various tracts, as well as areolar tissues lining cavities.

Deep Lymphatics

Accompany deep arteries and veins, supplying skeletal muscle, visceral walls, and organs in the neck, limbs, and trunk.

Thoracic Duct

Collects lymph from the body inferior to the diaphragm and the left side of the body superior to the diaphragm.

Cisterna Chyli

An expanded, sac-like chamber at L2 vertebra where the thoracic duct begins; receives lymph from the inferior abdomen, pelvis, and lower limbs.

Right Lymphatic Duct

Collects lymph from the right side of the body superior to the diaphragm.

Lymphedema

Blockage of lymphatic drainage from a limb, causing interstitial fluid accumulation and swelling.

Classes of Lymphocytes

T (thymus dependent) cells, B (bone marrow-derived) cells, and NK (natural killer) cells

Cytotoxic T Cells

Attack foreign cells or virus-infected body cells directly and are involved in cell-mediated immunity.

Helper T Cells

Stimulate the activation of both T and B cells.

Suppressor T Cells

Inhibit the activation and function of T and B cells.

B Cells

Differentiate into plasma cells, which produce and secrete antibodies for humoral immunity.

Antibodies

Proteins that bind to antigens and help destroy them.

NK Cells

Attack foreign cells, viral-infected body cells, or cancer cells and are involved in immunological surveillance.

Lymphopoiesis

Involves the bone marrow, thymus, and peripheral lymphoid tissue; generates lymphoid stem cells that form lymphocytes.

Lymphoid Tissues

Connective tissues dominated by lymphocytes, occurring in clusters deep to epithelia lining the respiratory, digestive (MALT), and urinary tracts.

MALT (Mucosa-Associated Lymphoid Tissue)

Collection of lymphoid tissues linked to the digestive system.

Tonsils

Large lymphoid nodules in the walls of the pharynx, including palatine, pharyngeal (adenoid), and lingual tonsils.

Lymphoid Organs

Lymphoid organs with a fibrous capsule, including lymph nodes, thymus, and spleen.

Afferent Lymphatics

Carry lymph to the node from the peripheral tissue.

Efferent Lymphatics

Attach at the hilum and carry lymph away from the node to the venous circulation.

Thymus

Located in the mediastinum, largest in infants, decreases in size after puberty (involution).

Spleen

Located inferior to the stomach, functions to remove abnormal blood cells, store iron, and initiate immune responses.

External Barriers (Nonspecific Defenses)

Physical barriers like skin, mucous membranes, and secretions that prevent infection.

Internal Defenses (Nonspecific Defenses)

Includes white blood cells (WBCs) and defensive proteins; phagocytes engulf microbes and debris.

Natural Killer (NK) Cells

Attack bacteria, virus-infected cells, and cancer cells by secreting perforins.

Interferons

Produced by activated lymphocytes, macrophages, and virus-infected cells; stimulate healthy cells to produce antiviral proteins.

Complement Proteins

Circulate in the blood and attach to microbes, causing them to lyse or be recognized by WBCs.

Inflammation

The body’s response to injured tissues, with symptoms of redness, heat, swelling, and pain.

Pyrogens

Chemicals that stimulate a fever, in order to discourage bacterial growth.