Biology 122 Spring, 2008

Laboratory 26

The Orbit and its contents

OBJECTIVES

At the end of this laboratory you should know and understand:

1. The major bony elements that form the walls of the orbit.

2. The bony structures of the orbit: fissures and foramina and the neural and vascular structures that pass through them (see “Structures of the Orbit” on the web site).

3. The origin, course, distribution, function of the cranial nerves (II, III, IV, V, VI and VII) associated with the eye, eyelids and orbit. The origin and distribution of sympathetic fibers to the eye should also be known.

4. The origin, insertion, innervation and function of the extraocular and palpebral muscles.

5. The structure, position and function of lacrimal apparatus, including: a) the lacrimal gland and its ducts; b) the parts that collect the secretions; and c) the terminal collecting system.

6. The origin and site of synapse of the parasympathetic fibers of CN VII to the lacrimal gland.

7. The origin, course, and distribution of the ophthalmic artery, anterior ethmoid artery and the supraorbital artery.

PRELAB PREPARATION

1. Study “Structures of the Orbit” on the web site.

2. Read descriptions of the orbit, the eyeball and its internal structure in your textbook (pp. 957 – 976). Concentrate on the structures of the orbit, rather than the eye itself

3. Review the functional components of the cranial nerves associated with the eye and orbit (pp 1132 - 1146). These include: II, III, IV, V₁ (ophthalmic division), VI and VII.

4. Review the origin, course and distribution of the sympathetic fibers distributed to the head, with specific reference to those distributed to the eye. Study the origin and site of synapse of the GVE parasympathetic fibers to the lacrimal gland and ciliary muscles of eye, and Special Visceral Efferent to orbicularis oculi (this does not pass through the orbit).