Question

A lymph node has many afferent vessels entering but a single efferent vessel leaving the node. Why is this important?

• A. To slow down the lymph retaining it for longer time in the node
• B. This gives more time for the macrophages to kill pathogens
• C. The lymph node is very small so it can accommodate only a single efferent vessel
• D. None of the above

Answer 1

Answer: (A), (B)

The correct options are
A To slow down the lymph retaining it for longer time in the node
B This gives more time for the macrophages to kill pathogens

The lymph has to flow slowly so that all the pathogens that it carries are effectively destroyed and the lymph flowing out of the lymph nodes is clean and clear of pathogens. To accomplish this the lymph has many afferent vessels bringing in unclean lymph from all parts of the body but just a single efferent vessel. This make the outflow very slow giving enough time for the lymph to stay in the nodes and immune cells to clear pathogens.