Embryology of the Lacrimal Drainage System

Abstract

The understanding of lacrimal embryology is very crucial to the understanding of lacrimal anatomy and its subsequent clinical and surgical applications. The lacrimal passages develop along the line of cleft between the maxillary process and the lateral nasal process [1–5]. The development of the lacrimal system begins at Carnegie Stage 16 (CRL, 11 mm), when an epithelial thickening of the lacrimal groove forms the lacrimal lamina [4]. At Carnegie Stage 19 (CRL, 17 mm), the lacrimal lamina separates from the surface ectoderm and forms the lacrimal cord. The lateral extreme of the cord closest to the surface ectoderm bifurcates, thus giving rise to the canaliculi (Fig. 1.2). At Carnegie Stage 20 (CRL, 19–21 mm), the lacrimal cord is arranged lateral to the nasal capsule and finally lateral and inferior to the inferior meatal lamina. At Carnegie Stage 22 (CRL, 26 mm), the cells of the lacrimal cord condense at its periphery but are more loosely organized centrally, toward the future lumen [4].