The Orbit

Laboratory Activity

Bony Orbit or Orbital Cavity

The orbit is also known as?

Orbit

It is a paired skeletal cavity within the skull that houses and protects the globe and its associated structures.

Quadrangular Pyramid

Shape of the orbit?

30mL

The adult orbit has an average volume of?

35mm

Height of the orbit?

40mm

Width at the orbital opening?

45mm

Medial orbital wall in mm?

~35mm

Lateral orbital wall in mm?

Globe

It is the most prominent structure within the globe.

Base of the Orbit

It provides structural support and serves as the attachment site for the orbital septum.

Apex of the Orbit

It is where the major neuromuscular structures pass into the orbital cavity.

Orbital Fat

It surrounds the globe and extra ocular muscles.

Orbital Fat

It acts as a cushion that absorbs mechanical forces while allowing smooth movement of the eye within the orbit.

Orbital Fascia

It provides additional structural support by stabilising the globe and surrounding tissues.

Lacrimal Apparatus

It is responsible for tear production and contributes to the maintenance of a healthy ocular surface.

Orbital Margin

Orbital Rim is also known as?

• Frontal

• Sphenoid

• Zygomatic

• Maxillary

• Palatine

• Ethmoid

• Lacrimal Bones

7 bones that form the orbit are the?

Orbital Rim

It forms the anterior opening of the orbit and represents the base of the pyramidal orbital cavity.

Orbital Roof

It provides a strong protective barrier between the orbit and the cranial cavity while also serving as the site for several important neuromuscular structures and muscular attachments.

Lateral Orbital Wall

Among the four orbital walls, it is considered the strongest and thickest, providing significant protection to the globe and the deeper orbital contents.

Lateral Orbital Tubercle

An important landmark on the lateral orbital wall is the Whitnall’s tubercle.

Whitnall’s Tubercle

Lateral Orbital Tubercle is also known as?

Medial Orbital Wall

It is the thinnest and most delicate wall of the orbit.

The medial wall is anatomically the thinnest, whereas the orbital floor is more frequently involved in orbital fractures because of the direction and mechanism of the blunt facial trauma.

Medial Wall vs. Orbital Floor

Orbital Floor

Inferior Wall of the Orbit is also known as?

Paper-thin plate

Lamina papyracea means?

Optic Foramen

Optic Canal is also known as?

Optic Canal

It transmits the optic nerve and the ophthalmic artery, the principal arterial supply to the orbit and globe.

Common Tendinous Ring

It surrounds the optic canal and the medial portion of the superior orbital fissure.

Ophthalmic Artery

The first major branch of the internal carotid artery.

Central Retinal Artery

It enters the optic nerve and supplies the inner layers of the retina.

Lacrimal Artery

It supplies the lacrimal gland, lateral rectus muscle, portions of the eyelids, and adjacent structures.

Superior Muscle Artery

It supplies the superior rectus and superior oblique muscles.

Inferior Muscular Artery

It supplies the inferior rectus, medial rectus, and inferior oblique muscles.

Venous Drainage of the Orbit

It is primarily accomplished by the superior ophthalmic vein and the inferior ophthalmic vein.

Superior Ophthalmic Vein

This vein is larger and more consistent of the two veins.

Inferior Ophthalmic Vein

This vein is larger and more consistent of the two veins

Superior and Inferior Ophthalmic Vein

These veins collect blood from the globe, extra ocular muscles, eyelids, lacrimal gland, and other orbital structures before draining posteriorly towards the cavernous sinus.

Sutures

The bones of the orbit are connected by fibrous joints known as?

Fascial Sheath of the Eyeball

Surrounding the globe is the Tenon’s capsule, also known as?

Orbital Septum

It provides structural support to the eyelids and helps contain the orbital fat within the orbital cavity.

Periorbita

It covers the internal surfaces of the orbital walls and serves as the attachment site for several ligaments and connective tissue structures.

Orbita Septum

This fibrous partition provides structural support to the eyelids and helps contain the orbital fat within the orbital cavity.

Lacrimal Gland

It is the principal secretory gland responsible for producing the aqueous component of the tear film.

Extension of Tenon’s Capsule

It contributes to the formation of the check ligaments and Lockwood’s suspensory ligament, which help stabilise the globe during eye movements.

• Larger Orbital Lobe

• Smaller Palbebral Lobe

Lacrimal Gland consists of two interconnected lobes:

Orbital Fat

It helps maintain the normal position of the globe while allowing smooth ocular movements.