Is a potential space that lie on either side of the larynx. They are two in number. It is shaped like a pyramid with the base point above and the apex below. They belong to the hypopharyngeal area of the pharynx. It has two parts; the shallow upper part and a deeper lower part.
Lateral - Mucosa lining the lamina of thyroid cartilage
Medial - Aryepiglottic fold and arytenoid cartilages above
cricoid cartilage below
Superiorly - lateral glosso epiglottic fold
Inferiorly - continues as the oesophagus
Deep to the mucous membrane of the pyriform fossa lies the internal laryngeal nerve branch of superior laryngeal nerve. This nerve supplies sensation to this area.
Importance of pyriform fossa:
1. Anatomically it is a hidden area. Any malignancy in this area will initially cause fewer symptoms and has a tendency to present late
2. This area is rich in lymphatics. These lymphatics drain into the upper deep cervical group of nodes. Malignancy in this area has a tendency for distant metastasis
3. Foreign bodies commonly gets lodged here
4. Since superior laryngeal nerve lies just under the mucosa of pyriform fossa it can be blocked using a gauze dipped in 4% xylocaine. This is known as pyriform fossa.
5. Pooling of saliva occurs in pyriform fossa if there is any obstruction in the food passage (Jackson's sign)