Crypts are anatomical structures that are narrow but deep invaginations into a larger structure.

One common type of anatomical crypt is the Crypts of Lieberkühn.^[1] However, it is not the only type: some types of tonsils also have crypts. Because these crypts allow external access to the deep portions of the tonsils, these tonsils are more vulnerable to infection.

• Histology image: 06601loa – Histology Learning System at Boston University - "Lymphoid Tissues and Organs: tonsil"
• Histology of crypt of tonsil at siumed.edu