Covers the orbit as a pyramid-shaped bony cavity: its shape and position, and how its axis diverges from that of the eyeball. It then goes through the roof, floor, medial and lateral walls with the bones forming each and the structures and relations that matter, followed by the openings and what passes through them, and finally the contents such as the eyeball, extraocular muscles, nerves, vessels and lacrimal apparatus. A labelled picture accompanies several sections.
Topic 10 of 236 in the MU Pleven syllabus for Anatomy Bones and Muscles (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 305 words (2 min of reading), with 14 flashcards.
In this note
Orbit – Anatomy Notes
Definition
Shape & Position
Boundaries of Orbit
Openings of Orbit
Contents of Orbit
Definition
The orbit is a bony cavity in the skull that contains and protects the eyeball and its associated structures (muscles, vessels, nerves, fat, glands).
Shape & Position
Shape: 4-sided pyramid (like an ice-cream cone)
Base: anterior opening → orbital margin
Apex: posterior end → at optic canal
Axis of orbit: points backward and medially
Axis of eyeball: points straight forward → so orbit and eyeball axes diverge ~23°
Boundaries of Orbit
Roof
Formed by: orbital plate of frontal bone (main), lesser wing of sphenoid (posteriorly)
Relations: above is anterior cranial fossa & frontal sinus
Important structures: trochlea (pulley for superior oblique muscle), lacrimal fossa (for lacrimal gland)
Floor
Formed by: maxilla (main), zygomatic bone, palatine bone (posterior small part)
