Which of the following structures are tubes?
A. Cilia, adenoids, mucous, epiglottis
B. Apex, base, hilum
C. Frontal, maxillary, sphenoidal, ethmoidal
D. Eustachian, pharynx, bronchi
To determine which of the structures mentioned are tubes, we need to understand what a tube is. A tube is a hollow and cylindrical structure that allows substances, such as air, fluids, or even cells, to pass through it. We can examine the given options and identify which structures possess these characteristics.
A. Cilia, adenoids, mucous, and epiglottis are not tubes. Cilia are hair-like structures on the surface of cells, adenoids are a collection of lymphoid tissue, mucous is a slimy substance, and the epiglottis is a flap of tissue that covers the windpipe during swallowing.
B. Apex, base, and hilum are not tubes. The apex refers to the pointed end of a structure, the base refers to the bottom or lower portion, and the hilum is a depression or an entrance into an organ.
C. The structures mentioned - frontal, maxillary, sphenoidal, and ethmoidal - are not tubes. They are the names of specific sinuses in the skull.
D. The structures Eustachian, pharynx, and bronchi are indeed tubes. The Eustachian tubes connect the middle ear to the back of the throat, the pharynx is the part of the throat that connects the mouth to the esophagus and nasal passages, and the bronchi are the major air passages in the lungs.
Therefore, the correct answer is D. Eustachian, pharynx, bronchi.