Mastoid process antrum begins to develop in the

*MASTOID* *ANTRUM* *DEVELOPEMENT* The antrum, which is the biggest of all mastoid air cells, stas its development between the 22nd and the 24th week of fetal life. It reaches its adult size on the 35th week The antrum develops at the center of the mastoid process on both sides of the petrosquamous fissure. The medial pa of the antrum, the petrous pa, develops from the saccus medius and the lateral pa, the squamous pa, develops from the saccus superior The fusion plane between the petrous pa and the squamous pa gives the petrosquamous fissure. Failure of complete fusion between the two sacci leads to a septation of the mastoid antrum by a bony paition called the Korner's septum Developmental arrest of the vestibule The antrum is well developed at bih and has a mean surface of 1 cm2 The size of the antrum does not change after bih; however, it undergoes medial displacement because of the growth of the mastoid process. The mastoid process continues to grow until pubey and even beyon REF : VISHRAM SINGH EMBRYOLOGY