anatomy of lymph node

LYMPH NODE

–oval, bean shaped structures scattered throughout body along lymph vessels–Usually 1-25 mm in length

–may be deep or superficial

–concentrated along the respiratory tree and GI tract, in the mammary glands, axillae, and groin

–filter lymph fluid to trap foreign organisms, cell debris, and tumor cells

generally...

Anatomical picture

Usually 1-25 mm in length, but they can be larger.

Greatest concentration near groin, axilla, neck, thorax, and along gut tube in abdomen.

Structure of a Lymph Node➢Outermost is the covering called capsule composed of fibrous connective tissue➢Capsule contains the parenchyma or stroma

➢Stroma is differentiated into cortex & medulla

•Trabeculae extend from cortex to medulla

Cortex

Medulla

- inner germinal center is the site of B-cell proliferation●inner medulla -medullary cords of lymphocytes, macrophages, plasma cells.

●outer cortex● - filled with lymph follicles -outer edge of follicle contains more T cells

Cytology of the lymph nodeThe normal or reactive lymph node is composed 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 are located primarily in the follicles and perifollicular areas

T lymphocytes are found primarily in the interfollicular or paracortical areas of the lymph node.

physiology

•Macrophages and lymphocytes reside in the outer ("cortex") region of a node.

●Afferent (entering) vessels bring lymph in.

●Lymph first enters into a large subcapsular sinus & then into many small sinuses.

●Throughout the node are lymph sinuses

crisscrossed by reticular fibers

•The node acts as a “settling tank,” because there are fewer efferent vessels, lymph stagnates somewhat in the

node.

•Macrophages reside on these fibers where they phagocytise foreign matter.

●This allows lymphocytes and macrophages time to carry out their protective functions●Reticular fibres filter and trap damaged cells, microorganisms, foreign substances, tumor cells.●Macrophages phagocytize some, lymphocytes destroy some by immune defenses.

"Medulla" is the inner collecting area. Efferent (exiting) vessel leaves at the "hilus.

Distribution

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 internal jugular 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

Horizontal group lies along the inguinal ligament (both above and over)

Vertical group is beside the great saphenous vein in the proximal thigh.

Iliac nodes:aboveand deep to inguinal ligament

Inguinal groups

3 cm proximal to the medial

humeral epicondyle, in the groove between

the biceps and triceps brachii.

Epitrochlear nodes

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