WHAT IS THE LACRIMAL APPARATUS?

The lacrimal apparatus is the system in the body that produces and drains tears. The lacrimal apparatus is made up of many parts, described below.

WHAT PARTS MAKE UP THE LACRIMAL APPARATUS?

The lacrimal apparatus is comprised of many parts. Here is a picture of some of these parts, followed by a brief description. Some parts that are described below are not in the picture.

• LACRIMAL GLANDS: Small organs that release tears. There are two types of lacrimal glands, known as main and accessory lacrimal glands. The main lacrimal glands (located in the upper and outer part of the eye sockets) release extra tears, such as when the eye is irritated and during crying. The main lacrimal glands drain tears into the conjunctiva. The conjunctiva is a layer that covers and protects the inside of the eyelids and the front part of the sclera (the white part of the eyes). Click here to see a picture of the conjunctiva. The accessory lacrimal glands (located within the conjunctiva) maintain a normal amount of tears on the surface of the conjunctiva. This helps overcome the effect of tears evaporating (changing from a liquid to a gas).

• LACRIMAL LAKE: A small open area of the conjunctiva of the eye where tears collect after bathing in the front part of the eyeball and in a slit-like space known as the conjunctival sac. The conjunctival sac is located between the eyelids and the conjunctiva-covered eyeball. See above for a description of the conjunctiva.

• EXCRETORY LACRIMAL DUCTS: Tube shaped areas that release tears from the lacrimal gland into the top part of the conjunctiva sac (see above).

• LACRIMAL PUNCTA: Tiny openings towards the inner part of each eyelid, that tears drain through. Picture the lacrimal puncta as being like a drain in a kitchen sink. The lacrimal puncta connect and send tears to narrow tubes, known as lacrimal canals.

• LACRIMAL CANALS (SUPERIOR & INFERIOR): Curved, tube shaped structures connected to the lacrimal puncta, that tears coming from the lacrimal lake drain into. As you can see in the picture, the superior (above) lacrimal canal is on the top and the inferior (below) lacrimal canal is on the bottom. Tears travel from the lacrimal canals to the lacrimal sacs. The lacrimal canals are also known as the lacrimal ducts and lacrimal canaliculi.

• LACRIMAL SACS: Hollow spaces that the lacrimal canals (see above) drain tears into. Each eye has a lacrimal sac for tears to drain into. The yellow structure pictured above, next to the lacrimal canals, is the lacrimal sac. Flat muscles that cover the lacrimal sac, squeeze and release it during blinking. This helps produce a suction effect that draws away extra tears when blinking. This is why people blink when they cry.

• LACRIMAL BONES: The bones that surround the lacrimal sac. They are located on each side of the nose, within the inner part of the eye socket.

• NASOLACRIMAL DUCTS: Tube shaped areas that are below the lacrimal sac and carry tears down through the bone, leading to an opening in the nose.

WHAT IS THE NASAL CAVITY AND INFERIOR NASAL CONCHAE SHOWN IN THE PICTURE ABOVE?

The nasal cavity is an opening on each side of the nose. The inferior nasal conchae are thin, spongy, bony plates in the nose.

WHY DO WE NEED TEARS ANYWAY?

The main function of tears is to keep the outer part of the eye and the conjuctiva moist. The conjunctiva is a clear layer that covers the whites of the eyes and the inner parts of the eyelids. Tears help keep the outer part of the eye clear and prevent it from developing sores. Tears also serve other roles such as helping express emotion, helping the eyelid move while blinking, and washing away material that gets in the eye from outside the body (such as dust and dirt). Tears also contain a natural substance called Iysozyme that fights off bacteria.

WHAT IS THE ORIGIN OF THE TERM, "LACRIMAL APPARATUS"?

Lacrimal apparatus comes from the Latin word "lacrima" meaning "tear," the Latin word "ad" meaning "toward," and the Latin word "parare" meaning "to make ready." Put the three words together and you have "toward to make ready tears."

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