Lymph node - structure and functional zones, sentinel lymph node, lymphatic tissue in organs, main lymphatic ducts

Structure and functional zones:

Lymph nodes are small, capsulated lymphoid tissue that are located along lymph vessels.

They are made of multiple functional zones:

CORTEX:

Outer cortex- mostly B cells. There is a germinal center that produces these cells.

Inner cortex (Paracortex)- contains T cells. The inner cortex has HEV (High endothelial venules)-->allows lymphocytes to enter the lymph node from the bloodstream.

MEDULLA:

Medullary cords- extensions of cortical tissue into the medulla

Medullary sinuses- spaces that divides the medullary cords-->lymph runs through towards the EFFERENT VESSEL

SINUSES:

Subcapsular sinus- located just under the capsule. It is the first place of lymph filtration. Contains MACROPHAGES.

Trabecular (cortical) sinus- found in cortex of lymph node, between the trabeculae. Provide a pathway for lymph to flow and provide interaction with immune cells

Medullary sinus- deliver lymph to the EFFERENT VESSELS

Sentinel lymph nodes:

-The first lymph nodes that cancer cells are most likely to spread to from a primary tumor. Used to determine the presence (or absence) of metastatic cancer.

Sorguis- left supraclavicular lymph node. This node is considered a sentinel lymph node in cases of abdominal cancer, particularly cancers originating in the stomach, pancreas, or esophagus

Virchow- inguinal region. This node is particularly associated with genital and lower abdominal cancers, such as those from the penis, vulva, or rectum.

Bayers- axillary sentinel lymph node. Important in drainage of breast. Therefore it is used to detect the spread of breast cancer.

Lymphatic tissue in organcs:

PRIMARY LYMPHATIC ORGANS- Places where immune cells (specifically LYMPHOCYTES) are produced and matured.

-Bone marrow- site of hematopoeisis. The production of both B-Lymphocytes and T-Lymphocytes occur here. However, the maturation of both differ in location. B-Lymphocytes are produced AND MATURED in the bone marrow

-Thymus- receives immature T-Lymphocytes from the bone marrow and matures them.

SECONDARY LYMPHATIC ORGANS- places in the immune system where mature immune cells are activated and engage with antigens. These organs are involved in immune responses and immune surveillance.

-Lymph nodes

-Spleen

-Tonsils

-Peyer's Patches

-Appendix

-MALT (Mucosa associated lymphatic tissue)

-GALT (Gut associated lymphatic tissue)

-BALT (Bronchus associated lymphatic tissue)

Main lymphatic ducts

There are 2 main lymphatic ducts in the body which drain the lymph into the venous circulation.

-RIGHT LYMPHATIC DUCT

The things that drain into it:

-Right jugular trunk

-Right subclavian trunk

-Right bronchomediastinal trunk

Where the right lymphatic duct drains into:

Right venous angle ( junction between right internal jugular vein and right subclavian vein)

-THORACIC DUCT

The things that drain into it:

-Left jugular trunk

-Left subclavian trunk

-Left bronchomediastinal trunk

-Left intercostal

-CISTERNA CHYLI- located at level of T12. It is formed from the confluence of INTESTINAL TRUNKS and LUMBAR LYMPHATIC TRUNKS

Where the thoracic duct drains into:

Left venous angle (junction between left internal jugular vein and left subclavian vein)