What does PH stand for?

Pharynx

The pharynx is an organ found in vertebrates and invertebrates, though the structure is not universally the same across the species. In humans the pharynx is part of the digestive system and also of the conducting zone of the respiratory system. The conducting zone also includes the nose, larynx, trachea, bronchi, and bronchioles, and their function is to filter, warm, and moisten air and conduct it into the lungs.