Chapter 39 – Lymphatics




Abstract




The lymphatic system is part of the systemic circulation. Its two main components are the conducting system and lymphoid tissue.





Chapter 39 Lymphatics




Describe the anatomy of the lymphatic system


The lymphatic system is part of the systemic circulation. Its two main components are the conducting system and lymphoid tissue.


Key aspects of the conducting system are:




  • Small lymphatic capillaries drain lymph into larger lymphatic vessels, which converge on the right lymphatic duct and the thoracic duct.



  • The right lymphatic duct is quite short (around 1.5 cm). It drains lymph into the right subclavian vein.



  • The thoracic duct (also known as the left lymphatic duct) is much larger, and drains into the left brachiocephalic vein. It collects lymph from the majority of the body (everywhere except the right arm, right chest and right side of the head and neck) and returns it to the systemic circulation.



  • Lymphatic vessels are pulled opened as a result of radial traction by the surrounding connective tissue. This permits fluid, proteins and even cells to enter. Like veins, lymph flow is promoted by skeletal muscle activity and deep inspiration. The larger lymph vessels have valves to ensure unidirectional flow.


The lymphoid tissue consists of:




  • Primary lymphoid organs – thymus and bone marrow. These organs are involved in the production of lymphocytes from progenitor cells.



  • Secondary lymphoid organs – these include lymph nodes and lymphoid follicles within the tonsils, spleen, Peyer’s patches and other mucosa-associated lymphoid tissue. This lymphoid tissue contains mature lymphocytes and is the site where foreign antigens activate the adaptive immune response (see Chapter 75).




Clinical relevance: central venous cannulation


Internal jugular and subclavian vein cannulation is a commonly performed procedure in major surgical and critical care patients. There is a long list of potential complications, including infection, air embolus, pneumothorax and arterial puncture.


Left-sided central venous cannulation also risks damage to the thoracic duct, which is in close proximity to the junction of the internal jugular and subclavian veins. Puncture of the thoracic duct can lead to a chylothorax. Damage to the thoracic duct can be prevented by using the right-sided internal jugular and subclavian veins, using a high-neck approach to the internal jugular vein and most importantly by cannulating under ultrasound guidance.

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Sep 27, 2020 | Posted by in ANESTHESIA | Comments Off on Chapter 39 – Lymphatics
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