Which of the following is not a speech organ?

Option 4 : Cervix 

Speech mechanism:

• Phonetics is the study and science of speech sounds. When we produce speech sounds we use the Speech Mechanism which comprises certain organs of the body, such as the muscles of the chest, the tongue, the lips, and so on.
• The movement of these organs causes some disturbance which travels to the ear of the listener in the form of sound waves. The listener then interprets them as sounds. The organs of speech perform different functions in the production of speech.
• In other words, the air that we breathe is modified in different ways to result in various combinations of consonants and vowels. That is probably why Speech is popularly known as 'modified breathing.'

The organs of speech and their speech functions can be described with reference to three systems: the Respiratory System, the Phonatory System, and the Articulatory System. 

• The Respiratory System: The organs of speech of which the Respiratory system is' comprised are the lungs, the muscles of the chest, and the windpipe or trachea. The windpipe through which the air we breathe in travels to the lungs, and the air we breathe out joins the outside air. 
• The Phonatory System is comprised of the larynx in the throat. The larynx is a muscular structure. The larynx contains a pair of muscular bands or folds called the vocal cords. These are placed horizontally from front to back, joined at the front but separated at the back. The space between the cords is called the glottis. 
• Pharynx is the part of the Articulatory System. The pharynx extends from the top of the larynx to the root of the tongue which lies opposite it. The muscles of the pharynx can greatly modify the shape and size of the pharyngeal cavity by contracting or expanding. Each modification affects the clarity of the sound we produce.

From the above points, it is clear that the cervix is not a speech organ.