Accessory Bones and Muscles of the Eye
By: Lance Schroeder and Kaycee Klinedinst

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Functions of the Accessory Bones and Muscles
The functions of the accessory bones are protection of the eyeball, provide points of attachment for muscles, house blood, production of cells, storage of inorganic salts, and to form passageways for blood vessels and nerves. The functions of the eye accessory muscles are movement of the eyeball which increases the range of vision.

Types of Eye Muscles
Extrinsic Muscles- The muscles of the eye have been designed to help stabilize and move the eyes in various directions. There are six extrinsic muscles which move the eye. These muscles arise from the bones of the orbit and connect by the broad tendons of the eye's tough outer surface. With any given eye movement more than one extrinsic muscle can be utilized, however each muscle is
only associated with one primary direction.

Intrinsic Muscles- These muscles enable the eye to focus and control the amount of light that enters the eye. The muscles are the iris sphincter which relaxes or contracts depending on light conditions, and the ciliary muscles, flattening or allowing the rounding of the lens of the eye to focus the light on retina.


Extrinsic Muscles of the Eye
Muscle Name
Function
Cranial Nerve Associated With Muscle
Superior Rectus
Rotates eye upward and towards midline
Oculomotor nerve III
Inferior Rectus
Rotates eye downward and towards midline
Oculomotor nerve III
Medial Rectus
Rotates eye toward midline
Oculomotor nerve III
Lateral Rectus
Rotates eye away from midline
Abducens nerve VI
Superior Oblique
Rotates eye ownward and away from midline
Trochlear nerve IV
Inferior Oblique
Rotates eye upward and away from midline
Oculomotor nerve III

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Actions of the Ocular Muscles



How the Intrinsic Muscles Aid in Focusing




Orbital Cavities
Orbital cavities are the bony cavities containing the eyeball along with its associated muscles, vessels and nerves. It is also called the eye socket or orbit. The orbit protects, supports, and maximizes the function of the eye. It is shaped like a quadrilateral pyramid. There are seven cranial and facial bones that conjoin to form the orbital structure.
The Seven Skull Bones That Make Up The Orbital Cavities
  1. Frontal
  2. Sphenoidexternal image 834279-835021-19tn.jpg
  3. Ethmoid
  4. Lacrimal
  5. Zygomatic
  6. Maxillary
  7. Palatine






What are the Functions of the Optic Foramen and the Supraorbital Fissure?
Optic Foramen- The optic foramen is the passage through the orbit (bony socket of the eye) of the eye in the lesser wing of the sphenoid bone, this opening allows a passage way for the optic nerve and the ophthalmic artery to enter the eye.

Supraorbital Fissure- The supraorbital fissure is the foramen between the greater and lesser wings of the sphenoid bone. This establishes a channel of communication between the middle cranial fossa and the orbit. There are five nerves and a vein that pass that pass through the fissure.
  • Oculomotor nerve (III)
  • Trochlear nerve (IV)
  • Ophthalmic division of the Trigeminal nerve (V)
  • Abducens nerve (VI)
  • Ophthalmic veins

Works Cited

"Actions of the Ocular Muscles." YouTube. YouTube, 06 Aug. 2008. Web. 07 Nov. 2013.

"Anatomy of the Eye." OphthoBookcom. N.p., n.d. Web. 04 Nov. 2013.

"How the Body Works : The Focusing Mechanism." YouTube. YouTube, 03 Aug. 2007. Web. 07 Nov. 2013.

"Medical Atlas." Medical Atlas. N.p., n.d. Web. 06 Nov. 2013.

"Muscles of Facial Expression." Muscle Identification. N.p., n.d. Web. 4 Nov. 2013.

"Orbit Anatomy ." Orbit Anatomy. N.p., n.d. Web. 07 Nov. 2013.

"Orbital Cavity." TheFreeDictionary.com. N.p., n.d. Web. 04 Nov. 2013.

Shier, David, Jackie Butler, and Ricki Lewis. Hole's Essentials of Human Anatomy & Physiology. 10th ed. New York:

McGraw-Hill, 2009. Print.

"Superior Orbital Fissure." TheFreeDictionary.com. N.p., n.d. Web. 04 Nov. 2013.

Swenson, Rand. "Chapter 4 - Extraocular Movement." Chapter 4: Eye Movements. Dartmouth, 2008. Web. 06 Nov. 2013.

The Eye: Structure and Function Discovery Education, 2004 . Full Video.