Human Anatomy - Kotsan I. Ya. 2009

Sense Organs
Visual Organ (Eye)
Lacrimal Apparatus

The lacrimal apparatus (apparatus lacrimalis) comprises the lacrimal gland and The system of lacrimal excretory ducts (Fig. 268).

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Fig. 268. Lacrimal apparatus of the right eye (after M. R. Sapin)

1 — lacrimal gland; 2 — upper eyelid; 3 — lacrimal canaliculus; 4 — lacrimal lake; 5 — lacrimal sac; 6 — nasolacrimal duct

The lacrimal gland (glandula lacrimalis) is a complex serous tubuloalveolar gland. It produces lacrimal fluid, commonly known as tears. The primary function of tears is to moisturize The surface of the Eyeball. Tears have a slightly alkaline reaction and consist mainly of Water containing about 1.5% NaCl, 0.5% albumin, and mucus. Additionally, tears contain Lysozyme, which exhibits pronounced bactericidal activity.

The lacrimal gland is located in the lateral angle of the upper wall of the Orbit, within the corresponding fossa. The tendon of the levator palpebrae superioris Muscle divides the gland into a larger upper orbital part (pars orbitalis) and a smaller lower palpebral part (pars palpebralis), which lies near the superior conjunctival fornix. Small accessory lacrimal glands (glandulae lacrimales accessoriae) may occasionally be found within the conjunctival fornix.

The excretory ducts (ductuli excretorii) of the lacrimal gland, numbering from 6 to 15, open into the conjunctival sac in the lateral part of the superior conjunctival fornix. The tears flowing from these ducts wash over the anterior part of the eyeball and eyelids, and via the lacrimal stream (rivus lacrimalis)—situated between the eyelid margin and the eyeball—drain into the medial corner of the eye, known as the lacrimal lake (lacus lacrimalis). From the lacrimal lake, tears enter the superior and inferior lacrimal canaliculi (canaliculi lacrimales). Each lacrimal canaliculus (upper and lower) begins in the lacrimal lake with a small opening, 0.25 mm in diameter, called the lacrimal punctum (punctum lacrimale), which is visible to the naked eye at the apex of the lacrimal papilla. Along its course, each canaliculus forms a bend directed superiorly in the upper canaliculus and inferiorly in the lower. Immediately after (medial to) this bend lies a slight dilatation, the ampulla of the lacrimal canaliculus (ampulla canaliculi lacrimalis). Continuing medially, both canaliculi narrow slightly and empty either together or separately into the lacrimal sac. The lacrimal sac (saccus lacrimalis) lies within the osseous fossa for the lacrimal sac, perfectly mirroring its shape. It features an upper, blind, slightly narrowed end called the fornix of the lacrimal sac (fornix sacci lacrimalis), and a lower, also somewhat narrowed end that transitions seamlessly into the nasolacrimal duct. The lacrimal part of the orbicularis oculi muscle is fused with the anterior wall of the lacrimal sac; upon contraction, it expands the sac, causing pressure within it to drop, which consequently draws tears into its cavity.

The nasolacrimal duct (ductus nasolacrimalis) is housed within the namesake canal of the Maxilla, measures 12–14 mm in length and 3–4 mm in diameter, and opens into the anterior part of the inferior nasal meatus beneath the Inferior nasal concha.