CONTENTS OF THE ORBIT

CONTENTS OF THE ORBIT

The orbit is a bony cavity in the front of the skull that houses the eyeball and its associated structures. It is a pyramid-shaped bone cavity with a base that forms the orbital plate of the frontal bone, a roof formed by the orbital plate of the sphenoid bone, and a floor formed by the orbital surface of the zygomatic bone and the maxilla.

NAME THE CONTENTS OF ORBIT

1. Eyeball
2. Extraocular muscles
3. Ciliary ganglion
4. Optic nerve
5. Lacrimal gland
6. Ophthalmic artery
7. Oculomotor nerve
8. Trochlear nerve
9. Abducens nerve
10. Nasolacrimal duct

DESCRIBE THE FASCIAE AROUND EYE BALL

1. Tenon's capsule: A fibrous layer that envelops the eyeball and is attached to the sclera.
2. Scleral fascia: A thin layer of fibrous tissue that covers the sclera.
3. Orbital fascia: A layer of fibrous tissue that forms the roof and floor of the orbit.
4. Conjunctival fascia: A thin layer of fibrous tissue that covers the conjunctiva.

Course and distribution of the ophthalmic nerve (V1):

The ophthalmic nerve arises from the trigeminal nerve (CN V) and enters the orbit through the superior orbital fissure.

• It gives off branches to the lacrimal gland, frontal sinus, and skin of the forehead.
• It divides into three branches: lacrimal, frontal, and nascociliary nerves.
• The lacrimal nerve supplies the lacrimal gland and surrounding skin.
• The frontal nerve supplies the frontal sinus and skin of the forehead.
• The nascociliary nerve gives off branches to the ciliary ganglion and the nasal cavity.

Blood vessels in the orbit:

• The ophthalmic artery is the main artery that supplies the orbit.
• It arises from the internal carotid artery and enters the orbit through the optic canal.
• It gives off branches to the eyeball, extraocular muscles, and surrounding tissues.
• The short posterior ciliary arteries supply the choroid and ciliary body.
• The long posterior ciliary arteries supply the ciliary body and choroid.

Connections and distribution of the ciliary ganglion:

The ciliary ganglion is a parasympathetic ganglion located in the orbit.

• It receives preganglionic fibers from the oculomotor nerve (CN III).
• It gives off postganglionic fibers to the ciliary muscle and sphincter pupillae muscle.
• The ciliary ganglion is connected to the oculomotor nerve via the short ciliary nerves.

Step-wise explanation of the connections and distribution of the ciliary ganglion:

1 → preganglionic fibers from the oculomotor nerve (CN III) enter the ciliary ganglion 2 → synapse occurs within the ciliary ganglion 3 → postganglionic fibers are transmitted to the ciliary muscle and sphincter pupillae muscle 4 → the ciliary muscle is responsible for changing the shape of the lens 5 → the sphincter pupillae muscle is responsible for constricting the pupilNote: This explanation is based on standard anatomy textbooks and is relevant to the MUHS exam format.