What would be the effect of blockage of the left subclavian trunk?

Question

An infection with a tropical parasite may block a lymphatic vessel. What would be the effect of blockage of the left subclavian trunk?

Answer 1

As always, it's useful to start by defining the important terms.

• Lymph is fluid which leaves the bloodstream as the net movement of fluid at capillaries is out of the bloodstream and into the surrounding tissues. The system of lymph vessels serves to absorb this fluid from the tissues and return it to the bloodstream in order to prevent the tissues from swelling as a result of the accumulation of this excess fluid.

• A lymph trunk is a large lymph vessel formed by the convergence of several other large lymph vessels. Lymph trunks empty into lymph ducts - the largest lymph vessels. There are 9 lymph trunks in the body.

• The left subclavian lymph trunk is found near the base of the neck (subclavian means below the collarbone) and mostly receives lymphatic drainage from the left arm.

So what would happen if this vessel were clogged? Fluid wouldn't be able to continue on to the thoracic duct (the lymph duct into which the left subclavian trunk empties) and would build up. Think of it like a traffic jam - the line of stopped cars continues to get longer. In this case that would mean that fluid is backing up in the lymph vessels that converge to form the left subclavian trunk.

So what happens when fluid builds up? Swelling! The traffic jam will lead to the left arm being swollen - this condition is called lymphedema.