Final answer:
The vocal cords, located in the larynx, vibrate to produce sound and open widely to allow for minimal resistance during breathing. Changing pitch involves altering vocal cord tension, and louder sounds result from increased airflow. The glottis, epiglottis, and mucus production also play roles in voice production and respiratory protection.
Step-by-step explanation:
The vocal cords, or true vocal cords, are a pair of folded, white membranes located in the larynx (voice box) with a free inner edge that oscillates as air passes through, producing sound. When the vocal cords open widely, they provide minimal resistance to airflow, which is essential for breathing rather than sound production. During speech or singing, these cords open and close rhythmically, creating variations in air pressure and causing the cords to vibrate, which in turn produces sound. If one wants to change the pitch of their voice, the muscles of the larynx can either relax or tighten, altering the tension of the vocal cords, while an increase in airflow from the lungs can make the voice louder, enhancing the amplitude of the sound pressure wave.
Another relevant anatomical feature is the glottis, an opening between the vocal folds through which air passes during speech. The size of the glottis and the tension of the vocal cords can significantly affect voice pitch and volume. Moreover, when swallowing, the epiglottis acts as a protective flap to prevent food from entering the airways.
Vocal cords also contribute to protecting the respiratory tract; located just above the trachea, these cords are part of an epithelial layer that produces mucus to trap debris and pathogens, with cilia moving mucus upward towards the throat for swallowing. This mechanism is vital for maintaining clear airways and preventing infections.