Lymphatic System Overview

Lymphatic System Overview

• The lymphatic system plays multiple crucial roles in the body, including absorbing dietary fats and lipid-soluble vitamins, removing excess extracellular fluid, acting as an immune filter for lymph, and providing a pathway for the spread of infections or malignancies.
• Lymph nodes, lymphoid organs, and lymphatic vessels are all integral parts of the system.
• Lymph node locations include the pharynx, tonsils (palatine, lingual, pharyngeal), respiratory tracts, skin, spleen, intestines (Peyer's patches, appendix), and urogenital tracts.
• Lymphoid tissue exists in various locations in the body.
• Lymph is formed when interstitial fluid enters lymphatic capillaries. This fluid is often termed lymph when it is in the lymphatic vessels.
• Lymph capillaries are microscopic vessels that collect interstitial fluid (lymph) and transport it to larger lymphatic vessels.
• Lymphatic capillaries, also known as lymph capillaries, are characterized by their unique 'one-way valve' structure; this helps prevent fluid backflow.
• The lymph travels through the lymphatic vessels, eventually draining into veins. Before entering the veins, lymph passes through lymph nodes, performing filtration.

Lymph Formation

• Lymph formation occurs in the tissue spaces, where lymph capillaries uptake interstitial fluid.
• Interstitial fluid is the fluid that exists between the cells in tissues.
• Blood capillaries are permeable, allowing some interstitial fluid to escape. This fluid becomes lymph once passed into the lymphatic capillaries.
• Lymphatic vessels have valves to prevent the backflow of lymph.
• Specialized endothelial cells with overlapping edges form the walls of lymphatic capillaries. The overlapping structure creates one directional flow.

Lymph Drainage

• Lymph drains into two main trunks: right lymphatic trunk (drains the right upper quadrant) and thoracic duct (drains the rest of the body).
• The right lymphatic trunk empties into the right subclavian vein.
• Lymph from the rest of the body is collected in the thoracic duct, which then drains into the left subclavian vein.
• The thoracic duct contains a swelling called the cisterna chyli.

Lymph Vessels

• Lymph vessels often run parallel to arteries in the body.
• The pulsatile nature of the arteries helps to push the lymph along.
• Lymph vessels typically follow an arterial pattern.

Imaging

• Imaging techniques such as ultrasound and CT scans are used to diagnose lymphatic system pathology.
• There are various imaging methods to assess the lymphatic system.

Absorption

• Lymph plays a role in nutrient absorption. Specifically, it transports absorbed dietary fats and lipid-soluble vitamins from the digestive tract to the bloodstream.
• Lymph vessels collect and transport absorbed fats from the small intestine.

Immune Function

• Lymphatic tissue serves as an essential filter for lymph, trapping and removing foreign particles, such as bacteria and viruses.
• The lymphatic system actively contributes to the immune response.
• Lymphoid tissue is associated with both primary and secondary lymphoid organs, crucial for immune responses. Cell-mediated and antibody-mediated responses are two significant components of the immune response.

Lymph Nodes

• The human body has approximately 500-600 lymph nodes.
• Lymph nodes are crucial for the immune response, as they filter lymph and contain immune cells.
• Within lymph nodes, B-cells reside in the outer cortex, while T-cells reside in the inner cortex.

Spleen

• The spleen is a vital lymphoid organ responsible for filtering blood and responding to infections.
• The spleen's structure is comprised of red pulp (filtering blood) and white pulp (immune responses).

Thymus

• The thymus is an important primary lymphoid organ, playing a critical role in the development of T-cells.
• Thymus function typically declines with age.

Pathology

• Various pathologies, such as lymphadenitis, lymphadenopathy, lymphedema, and lymphangitis, affect the lymphatic system.
• Imaging techniques contribute significantly to diagnosing lymphatic system diseases.

Sentinel Lymph Node Biopsy

• In breast cancer, sentinel lymph node biopsy is a procedure employed to detect the presence of cancer cells to determine whether lymph node metastasis has occurred.
• The technique involves injecting a radioactive tracer or colored dye into the area surrounding the tumor to identify the sentinel lymph node(s) which are the first lymph nodes draining that region. These nodes are then excised and examined for the presence of cancer.
• If cancer is found in the sentinel(s) lymph node(s) , a complete axillary lymph node dissection is often subsequently conducted.

Neck Lump/Lymphadenopathy

• Neck lumps and lymphadenopathy are conditions involving abnormal swelling of lymph nodes in the neck region.
• Possible causes often necessitate further medical evaluation and testing.