Lacrimal Apparatus

The eyeball is suspended in the orbit and faces outward. Helping to fill the orbit are a number of structures associated with the eyeball; these are the adnexa. Among these other structures is the lacrimal apparatus.

a. The lacrimal gland is located in the upper outer corner in front. Via small ducts, it secretes the lacrimal fluid into the space between the external surface of the eyeball and the upper eyelid.

b. The inner surface of the eyelids and the outer surface of the eyeball are covered by a continuous membrane known as the conjunctiva. The lacrimal fluid keeps the conjunctiva transparent. Also, with the blink reflex, the lacrimal fluid washes away any foreign particles that may be on the surface of the conjunctiva.

c. The free margins of the upper and lower eyelids have special oil glands. The oily secretion of these glands helps prevent the lacrimal fluid from escaping.

d. With the movement of the eyeball and the eyelids, the lacrimal fluid is gradually moved across the exterior surface of the eyeball to the medial inferior corner. Here, the lacrimal fluid is collected into a lacrimal sac, which drains into the nasal chamber by way of the nasolacrimal duct. Thus, the continuous production of lacrimal fluid is conserved by being recycled within the body.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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