Which direction do cilia beat to move mucus toward the pharynx?

Cilia are microscopic hair-like structures lining the respiratory tract, including the trachea and bronchi, playing a crucial role in mucociliary clearance. They beat in a coordinated, wave-like manner to move mucus and trapped particles upwards towards the pharynx. This upward movement is essential for maintaining clear airways, as it helps to clear debris and pathogens from the lungs and respiratory passages.

The directionality of the ciliary movement is important for effective mucous transport. Mucus traps inhaled particles and microorganisms; by moving this mucus upwards, cilia facilitate its eventual swallowing or expulsion. This process is vital for protecting the respiratory system from infections and ensuring that the airways remain unobstructed. Thus, the correct answer reflects the physiological function of cilia in the respiratory system, highlighting their role in maintaining respiratory health.