Question

Although all of the structures of the respiratory system are in contact with the circulatory system, which respiratory structure is most closely associated with dense network of capillaries?

A. pharynx
B. vocal folds
C. trachea
D. alveoli

Answer 1

Here is a picture of an alveoli

http://www.visualphotos.com/photo/1x3747285/alveolus_in_lung_alveoli_of_the_lungs_colored_scanning_electron_micrograph_sem_of_a_section_th_P4490.jpg

Answer 2

alveoli