Which airway segment is the smallest lacking cartilage but with abundant smooth muscle?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

As airways get smaller, cartilage support disappears and smooth muscle becomes the main modulator of diameter. The bronchioles are the smallest airway segments that lack cartilage while still containing abundant smooth muscle, so they can constrict or dilate to regulate resistance to airflow. The trachea has cartilage rings, and bronchi have cartilage plates, which stop before reaching the bronchioles. Alveoli, by contrast, are gas-exchange sacs with no cartilage or smooth muscle. The ability to adjust airway size mainly at the bronchioles explains why this segment fits the description.