Excretory system, lacrimal

Figure 24-4 Cut-away view showing the lacrimal excretory system. Tears drain through the punctum (A) and eventually under the inferior turbinate bone of the nose. Dimensions of the canaliculi serve as references for probing and irrigation. B, canaliculus C, common canaliculus. (Redrawn with permission from Jones LT. Ophthalmic anatomy a manual with some clinical appHcations. 1. The orbital adnexa. Am Acad Ophthalmol 1970 70.)...

The nasolacrimal drainage system consists of three parts the secretory systan, the distributive system, and the excretory system. The secretory portion is composed of the lacrimal gland that secreted tears and is spread over the ocular surface by the eyelids during blinking. The secretory system is stimulated by blinking and temperature change due to tear evaporation and reflux secre-tors that have an efferent parasympathetic nerve supply and secrete in response to a physical and emotional state, for example, crying. 

Diseases and disorders involving the lacrimal system are among the more common conditions experienced by ophthalmic patients, with as many as 25% complaining of dry eye symptoms alone.The lacrimal system is most easily considered as having three components—the secretory system, the distribution system, and the excretory or drainage system.These components must work in harmony to support a healthy, moist, and comfortable ocular surfece. 

The excretory part of the nasolacrimal drainage system consists of the lacrimal puncta the superior, inferior, and conunon canaliculi the lacrimal sac and the nasolacrimal duct. In humans, the two puncta are the openings of the lacrimal canaliculi and are situated on an elevated area known as the lacrimal papilla. It is thought that tears are largely absorbed by the mucous membrane that lines the ducts and the lacrimal sac only a small amount reaches the nasal passage. 

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