generally...–oval, bean shaped structures scattered throughout body along lymphvessels–Usually 1-25 mm in length–may be deep or superficial–concentrated along the respiratory tree and GI tract, in the mammaryglands, axillae, and groin–filter lymph fluid to trap foreign organisms, cell debris, and tumor cells
Usually 1-25mm in length,but they canbe larger.Greatestconcentrationnear groin,axilla, neck,thorax, andalong guttube inabdomen.
Structure of a Lymph Node➢Outermost is the covering called capsulecomposed of fibrous connective tissue➢Capsule contains theparenchyma or stroma➢Stroma isdifferentiated intocortex & medulla•Trabeculae extendfrom cortex to medulla
● outer cortex ● - filled with lymph follicles -outer edge of follicle contains more T cells- inner germinalcenter is the site of B-cell proliferation●inner medulla-medullary cords oflymphocytes, Cortexmacrophages, plasmacells. Medulla
Cytology of the lymph nodeThe normal or reactive lymph node iscomposed of ➢ Transient B and T lymphocytes➢ Antigen processing and presenting cells➢ Replicating B and T lymphocytes (in response to antigen)➢ Persistent and transient final effector cells➢ Macrophages
B lymphocytes arelocated primarily in the follicles andperifollicular areas T lymphocytes arefound primarily in the interfollicular orparacortical areas of the lymph node.
•Macrophages and lymphocytes reside in theouter ("cortex") region of a node.Afferent (entering) vessels bring lymph in.●●Lymph first enters into a large subcapsularsinus & then into many small sinuses.●Throughout the node are lymph sinusescrisscrossed by reticular fibers
•Macrophages reside on these fibers wherethey phagocytise foreign matter. •The node acts as a “settling tank,” because there are fewer efferent vessels, lymph stagnates somewhat in the node.
●This allows lymphocytes and macrophages timeto carry out their protective functions●Reticular fibres filter and trap damagedcells, microorganisms, foreign substances, tumorcells.●Macrophages phagocytize some, lymphocytesdestroy some by immune defenses. "Medulla" is the inner collecting area. Efferent (exiting) vessel leaves at the "hilus.
Lymph nodes of clinical importance have been put under 5 main groups:➢ Cervical groups➢ Axillary groups➢ Inguinal groups➢ Epitrochlear lymph nodes➢ Popliteal lymph nodes
Cervical groups● Right & left groups● each divided into: horizontal (circular)and vertical The horizontal group include: > sub-mental > sub-mandibular > parotid > pre-auricular > post-auricular > occipital
The vertical group include:> superficial (along external jugular vein) > deep (along internaljugular vein) > Prelaryngeal > Pretracheal > Paratracheal
Axillary groups● Right & left groups● each divided into 5 groups: > Anterior (pectoral) > posterior (sub-scapular) > medial (along chest wall) > lateral (humeral) > central
Inguinal groups Horizontal group lies along theinguinal ligament (both above and over) Vertical group is beside thegreat saphenous vein in the proximal thigh.Iliac nodes:aboveand deep to inguinalligament
Epitrochlear nodes 3 cm proximal to the medialhumeral epicondyle, in the groove between thebiceps and triceps brachii.