Pharynx is a funnel shaped tube about 13cm long that starts at the internal nares and extends to the level of the cricoid cartilage. It lies posterior to the nasal and oral cavities, superior to larynx and just anterior to the cervical vertebrae. Its walls are composed of skeletal muscles and lined by mucous membrane. Three parts of pharynx are nasopharynx, oropharynx and laryngopharynx. The nasopharynx is posterior to nasal cavity. The two internal nares, to eustachian tubes and the oropharynx are the openings of nasopharynx. Oropharynx lies posterior to oral cavity, extends from the soft palate inferiorly to the level of hyoid bone, lined with non-keratinized stratified squamous epithelium. Two pairs of tonsil are found in oropharynx. Laryngopharyx begins at the layer of hyoid bone, lined by non-keratinized stratified squamous epithelium, opens into oesophagus posteriorly and the larynx anteriorly. Pharynx serves as a passage way for air, food and drink, and provides resonating chamber for speech sounds.
Larynx or voice box is a short passage way that connects the laryngopharynx with trachea. It lies in the midline of the neck anterior to oesophagus and corresponds with the levels of cervical 4 to 6 vertebrae. Its wall is composed of nine pieces of cartilage-3 single-thyroid, epiglottis and cricoid and 3 in pairs- arytenoid, cuneiform and comiculate cartilages. Arytenoid influencerhe positions and tensions of vocal folds. Thyroid cartilage, two fused plates of hyaline cartilage to form the anterior wall of the larynx giving a triangular shape. Epiglottis is large, leaf shaped having a stem which is attached to the anterior rim of the thyroid cartilage and hyoid bone and a broad superior 'leaf' portion unattached and free to move up and down. During swallowing epiglottis moves down and forms a lid over glottis closing the entrance to larynx to prevent the entry of food or drink. When small particles of food, drink or dust enter the larynx a cough reflex occurs to expel the material.
Arytenoid cartilages are two small structures situated on the upper surface of the expanded signet portion of the cricoids cartilage. They give attachment to the posterior ends of the true vocal cords. The true vocal cords are fibro elastic bands extending from the posterior aspects of the thyroid cartilage in front to the arytenoids cartilage behind. The false vocal cords are two loose folds of mucous membrane situated above the true cords. Larynx is lined by mucous membrane which, except over the vocal cords, is covered with ciliated columnar epithelium.