Excretory system Figure

The puncta on the medial aspect of the upper and lower lid margins mark the opening of the lacrimal drainage system. Each leads into a 2mm vertical dilatation of the canaliculus (ampulla) followed by an 8 to 10mm horizontal portion. It is important to recognise this canalicular configuration when performing tear sac wash-out and to hold the lid taut during the procedure. The superior and inferior canaliculus combine to form the common canaliculus which leads into the lacrimal sac. Its entry into the sac is normally partially covered by a flap of mucosa (Valve of Rosenmuller).

Superior canaliculus

Common canaliculus

Superior canaliculus

Common canaliculus

I 10mm [ body of sac

12mm > interosseous part

Inferior canaliculus

Figure 1.2 Lacrimal drainage system.

I 10mm [ body of sac

12mm > interosseous part

Lacrimal sac

Nasolacrimal duct

Inferior canaliculus

Figure 1.2 Lacrimal drainage system.

The lacrimal sac leads into the nasolacrimal duct. The duct has an upper intraosseous (12mm) segment, the direction of which is inferior and slightly lateral and posterior. The lower intramembranous segment (5mm) opens into the lateral wall of the nose beneath the inferior turbinate. The ostium is covered by a mucosal valve (of Hasner). The tear flow is actively pumped from the tear lake by the actions of the orbicularis muscle (Figure 1.3).

Figure 1.3 The lacrimal pump.

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