Also known as the piriform sinus (and sometimes wrongly spelt “pyriform”).The two piriform fossae (sinuses) are pear-shaped recesses on either side of the laryngeal inlet with the wider part anteriorly. Each has a medial wall formed by the aryepiglottic fold and an outer wall by the inner part of the thyroid cartilage and thyrohyoid membrane. There function is to provide channels for food to pass down during swallowing and the space within the fossa acts as a resonating chamber during speech and singing.