abnormalities aging anatomy anthropometry arabiclanguage careandhygiene child children choralsinging comparative diagnosis histology infant instructionandstudy mammals obstructions pathophysiology phonetics physiologicalaspects physiology physiopathology respirationdisorders respiratoryorgans speech surgery therapy trachea vocalcords voice voicedisorders ws280p36631995 wv500c725u1996 wv501c915h1987 wv501h318a1995