Final answer:
The tonsils located in the throat, including the palatine, lingual, pharyngeal, and tubal tonsils, defend against bacterial invasion through the mouth and nose. They are part of Waldeyer's ring and play an important role in the immune system's response to pathogens.
Step-by-step explanation:
The lymphoid organ(s) located in the throat that defend(s) against invading bacteria through the mouth and nose are the tonsils. These include the palatine tonsils which are visible on either side of the throat, the lingual tonsils located below the tongue, the pharyngeal tonsils located in the back of the nasal cavity, and the tubal tonsils located at the back of the nasopharynx.
The tonsils are part of Waldeyer's ring, which is a ring of lymphoid tissue located where the respiratory and gastrointestinal tracts intersect, providing an excellent site for the immune system to interact with incoming pathogens. The palatine tonsils, specifically, are often the ones implicated in throat infections and may swell when actively fighting an infection, which can obstruct breathing or swallowing in severe cases.